OM606 fuel supply issues
OM606 fuel supply issues
What got me going on this was the the engine had poor power and ran just a little rough past about 2800rpm. There was one exception though, and that was when the fuel tank was full, right up to the lip. The other clue was that one could see bubbles in the clear fuel lines whenever the engine was revved up (out of gear).
The answer is that A) the fuel system was poorly designed (by Bosch); and, B) not even built (by MB) the way it was designed. This gets to be a long story, but the basic problem is that the lift pump pulls so hard that it pulls gasses out of the diesel fuel on its intake stroke. Those gasses do not diffuse back into the fuel during the delivery stroke (basic physics). Once the bubbles form, they are in the system for a long time. This is because getting gasses out of solution is much easier (and faster) than diffusing a large bubble back in to the solution. The bubbles are large in the line before the fine fuel filter and get chopped into 10 micron bubbles by the filter. The tiny bubbles are harder to see, but they are still gas bubbles and haven’t recombined into the liquid. Since they are compressible, when the IP plunger starts delivering fuel it first has to compress the bubbles to the injector opening pressure, that introduces a delay in timing. Also, since part of the chamber was filled with gas, that effectively reduces the total fuel delivery. Both problems reduce power.
Background: The diagnosis took a while. As I said earlier, I’ve noticed bubbles in the line going to the fine fuel filter at elevated RPM’s. I always assumed that the problem was due to air sneaking past the o-rings. I believed this even though the leaks continued with fresh o-rings. How wrong I was.
Recently, while doing some work with the intake manifold off, I decided to run an experiment. I installed some clear soft 8mm Tygothane tubing in place of the line going from the tank to the fuel heater/thermostat. There were no bubbles in the line. In fact there were no bubbles anywhere in the system. Aha! I said. The fuel line must have been leaky. I did notice that the soft clear line was pulsating wildly with each stroke of the lift pump. Just for fun I squeezed the line with my fingers to see if that would kill the engine. As I started to squeeze the line, a foam of bubbles appeared in the flow just after the pinch spot. Clearly the tube wasn’t leaking. Rather, the suction of the pump was lowering the tube pressure below the vapor pressure of diesel fuel. Thinking about this more, I realized that the reason that the bubbles had disappeared was because the pulsating line was providing pressure stabilization. So, the conclusion is that pressure (or rather vacuum) pulses are the cause of the bubbles.
Now for the design mistakes. The OM606 has no hand primer. Bosch needed a way to self-prime the system before the battery died. They chose to increase the volume of the lift pump and re-design the overflow return valve. In the past, the valve was designed to maintain a minimum pressure in the IP. In order to self-prime, the OM606 valve was re-designed as a simple one-way valve with a rather large opening. It prevents fuel from flowing backwards, but provides little flow restriction. The pump and valve together can move a lot of fuel, more fuel than the old fuel lines were designed for.
“No problem”, the Bosch engineers said, “we’ll just make the fuel line bigger”. They made the inlet to the fuel thermostat ~10mm rather than the old 8mm. The larger pipe will flow 56% more fuel. What could go wrong? Well, the MB bean-counters got in there and managed to make it go wrong. To save money, they installed an 8mm hose with a ~10mm bulge at the end. Worse, they connected this to a thick walled fuel line that is <6mm in the inside and almost 3M long. The steel line only flows ~36% of the intended Bosch design. That restriction is enough to ensure massive pressure pulses. Ooops.
Technically, a 6mm ID tube would flow the required 3lpm. But only if that flow were smooth. Unfortunately the flow is driven by a piston pump at 1/2 RPM and it is definitely not smooth. It is the pulses that cause the vacuum and thus the bubbles.
This design is present on the E and G. The problem is made worse on the G, because the fuel needs to be lifted up ~20cm, even on flat ground. The G always ran better if I filled the G up all the way to the edge of the opening. After the first liter was burned off, performance returned to “normal”. The extra performance was because fuel was being pushed into the fuel line, rather than pulled. On a steep upslope this is, of course, even worse.
At altitude there is another phenomenon. Since the fuel system is a suction system, the only reason that fuel flows is because the pump inlet is at a lower pressure than the tank. From a basic physics perspective, air pressure in the tank is pushing the fuel into the lift pump. As you go higher there is less and less air pressure pushing on the fuel. So, all the problems listed above just get worse. On my G the problem can be severe at >3000M. With a low tank at 4000M the fuel line is full of bubbles and it hardly moves at all.
Simply because I had it handy, I installed a long 8mm hose all the way to the tank, eliminating the steel line. This noticeably improved the performance, particularly in uphill passing.
Request: Does someone have a OM606 fuel thermostat in hand? I'd like a verification of the inlet neck measurement. I recall 10mm, but it might have been 1mm larger or smaller. I don’t want to take off the manifold just to measure that. I need the measurement at the neck not the bead.
I thought I'd post some things I've discovered about the OM606 fuel system. You folks are always interested in performance issues and this is a basic design flaw in the MB implementation. While this is a bit of an oddball case (OM606 in a G-wagen - WDB46333117106xxx), the issues also apply to the OM606 in the E-class and probably in the S-class, too. The underlying issues are probably applicable to a wide range of inline IP pump diesels.
What got me going on this was the the engine had poor power and ran just a little rough past about 2800rpm. There was one exception though, and that was when the fuel tank was full, right up to the lip. The other clue was that one could see bubbles in the clear fuel lines whenever the engine was revved up (out of gear).
The answer is that A) the fuel system was poorly designed (by Bosch); and, B) not even built (by MB) the way it was designed. This gets to be a long story, but the basic problem is that the lift pump pulls so hard that it pulls gasses out of the diesel fuel on its intake stroke. Those gasses do not diffuse back into the fuel during the delivery stroke (basic physics). Once the bubbles form, they are in the system for a long time. This is because getting gasses out of solution is much easier (and faster) than diffusing a large bubble back in to the solution. The bubbles are large in the line before the fine fuel filter and get chopped into 10 micron bubbles by the filter. The tiny bubbles are harder to see, but they are still gas bubbles and haven’t recombined into the liquid. Since they are compressible, when the IP plunger starts delivering fuel it first has to compress the bubbles to the injector opening pressure, that introduces a delay in timing. Also, since part of the chamber was filled with gas, that effectively reduces the total fuel delivery. Both problems reduce power.
Background: The diagnosis took a while. As I said earlier, I’ve noticed bubbles in the line going to the fine fuel filter at elevated RPM’s. I always assumed that the problem was due to air sneaking past the o-rings. I believed this even though the leaks continued with fresh o-rings. How wrong I was.
Recently, while doing some work with the intake manifold off, I decided to run an experiment. I installed some clear soft 8mm Tygothane tubing in place of the line going from the tank to the fuel heater/thermostat. There were no bubbles in the line. In fact there were no bubbles anywhere in the system. Aha! I said. The fuel line must have been leaky. I did notice that the soft clear line was pulsating wildly with each stroke of the lift pump. Just for fun I squeezed the line with my fingers to see if that would kill the engine. As I started to squeeze the line, a foam of bubbles appeared in the flow just after the pinch spot. Clearly the tube wasn’t leaking. Rather, the suction of the pump was lowering the tube pressure below the vapor pressure of diesel fuel. Thinking about this more, I realized that the reason that the bubbles had disappeared was because the pulsating line was providing pressure stabilization. So, the conclusion is that pressure (or rather vacuum) pulses are the cause of the bubbles.
Now for the design mistakes. The OM606 has no hand primer. Bosch needed a way to self-prime the system before the battery died. They chose to increase the volume of the lift pump and re-design the overflow return valve. In the past, the valve was designed to maintain a minimum pressure in the IP. In order to self-prime, the OM606 valve was re-designed as a simple one-way valve with a rather large opening. It prevents fuel from flowing backwards, but provides little flow restriction. The pump and valve together can move a lot of fuel, more fuel than the old fuel lines were designed for.
“No problem”, the Bosch engineers said, “we’ll just make the fuel line bigger”. They made the inlet to the fuel thermostat ~10mm rather than the old 8mm. The larger pipe will flow 56% more fuel. What could go wrong? Well, the MB bean-counters got in there and managed to make it go wrong. To save money, they installed an 8mm hose with a ~10mm bulge at the end. Worse, they connected this to a thick walled fuel line that is <6mm in the inside and almost 3M long. The steel line only flows ~36% of the intended Bosch design. That restriction is enough to ensure massive pressure pulses. Ooops.
Technically, a 6mm ID tube would flow the required 3lpm. But only if that flow were smooth. Unfortunately the flow is driven by a piston pump at 1/2 RPM and it is definitely not smooth. It is the pulses that cause the vacuum and thus the bubbles.
This design is present on the E and G. The problem is made worse on the G, because the fuel needs to be lifted up ~20cm, even on flat ground. The G always ran better if I filled the G up all the way to the edge of the opening. After the first liter was burned off, performance returned to “normal”. The extra performance was because fuel was being pushed into the fuel line, rather than pulled. On a steep upslope this is, of course, even worse.
At altitude there is another phenomenon. Since the fuel system is a suction system, the only reason that fuel flows is because the pump inlet is at a lower pressure than the tank. From a basic physics perspective, air pressure in the tank is pushing the fuel into the lift pump. As you go higher there is less and less air pressure pushing on the fuel. So, all the problems listed above just get worse. On my G the problem can be severe at >3000M. With a low tank at 4000M the fuel line is full of bubbles and it hardly moves at all.
Simply because I had it handy, I installed a long 8mm hose all the way to the tank, eliminating the steel line. This noticeably improved the performance, particularly in uphill passing.
Request: Does someone have a OM606 fuel thermostat in hand? I'd like a verification of the inlet neck measurement. I recall 10mm, but it might have been 1mm larger or smaller. I don’t want to take off the manifold just to measure that. I need the measurement at the neck not the bead.
If not, a electric pump could be a good up grade,(improved performance). Although the old stroker pump is dependable.
Looking for answers (not guesses )
Thanks for sharing;good write-up. Would a electric pump near tank solve this problem? Lift pump pressure jumps wildly on the 617,616 and others also. WHY not a steady flow,at least on the pressure side. Dropping from 1 bar pressure to zero with every stroke of the pump. Was this in the design??? Is there any way the fuel to inter the oiling system in the injection pump?
If not, a electric pump could be a good up grade,(improved performance). Although the old stroker pump is dependable.
Looking for answers (not guesses )
(08-21-2012, 03:18 PM)Hercules Thanks for sharing;good write-up. Would a electric pump near tank solve this problem? Lift pump pressure jumps wildly on the 617,616 and others also. WHY not a steady flow,at least on the pressure side. Dropping from 1 bar pressure to zero with every stroke of the pump. Was this in the design??? Is there any way the fuel to inter the oiling system in the injection pump?A pump would certainly work. From a performance perspective, the ideal would be to remove the existing lift pump and add a 1-2bar electric pump at the tank. I take the G out to remote places and I'm not sure I want to depend on just the electric pump. I'm tempted to put a small pump at the tank, in-line with the existing lift pump. There are some low pressure pumps (0.3 bar) that are flow-through, meaning that if the electric pump fails, the lift pump can keep drawing.
If not, a electric pump could be a good up grade,(improved performance). Although the old stroker pump is dependable.
Looking for answers (not guesses )
For now, I'm going to reduce the restrictions in the line, or perhaps add some sort of fuel buffer near the lift pump (the fluid equivalent of a capacitor). I have yet to find such a device though. The shut off valve is another suspect. It seems to have some internal restrictions and is really not very useful since the IP stops injecting fuel whenever the rack solenoid current is cut off.
(08-21-2012, 03:18 PM)Hercules Thanks for sharing;good write-up. Would a electric pump near tank solve this problem? Lift pump pressure jumps wildly on the 617,616 and others also. WHY not a steady flow,at least on the pressure side. Dropping from 1 bar pressure to zero with every stroke of the pump. Was this in the design??? Is there any way the fuel to inter the oiling system in the injection pump?A pump would certainly work. From a performance perspective, the ideal would be to remove the existing lift pump and add a 1-2bar electric pump at the tank. I take the G out to remote places and I'm not sure I want to depend on just the electric pump. I'm tempted to put a small pump at the tank, in-line with the existing lift pump. There are some low pressure pumps (0.3 bar) that are flow-through, meaning that if the electric pump fails, the lift pump can keep drawing.
If not, a electric pump could be a good up grade,(improved performance). Although the old stroker pump is dependable.
Looking for answers (not guesses )
For now, I'm going to reduce the restrictions in the line, or perhaps add some sort of fuel buffer near the lift pump (the fluid equivalent of a capacitor). I have yet to find such a device though. The shut off valve is another suspect. It seems to have some internal restrictions and is really not very useful since the IP stops injecting fuel whenever the rack solenoid current is cut off.
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
sassparilla_kid
08-21-2012, 04:19 PM #4So for your fuel buffer, you need some sort of semi rigid (or semi flexible depending on how you look at it) container that can flex with the pump pulses? Flex enough that the vacuum won't be able to pull the gases out of the diesel, yet rigid enough that it won't get sucked flat?
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
That is why I'm leaning towards a larger and softer fuel line. The larger fuel line will introduce less resistance and the flex will help absorb the pulses.
There are more benefits than just getting the full power out of the engine. With no bubbles in the fuel, the timing is spot on and the spray pattern is better. Thus it smokes much less on hard acceleration and appears to get better mileage. I'm showing ~10% better, but need several more tank fills to prove that.
It would be really great if someone with an OM606 or OM605 could measure the diameter of the inlet to the fuel thermostat.
Yes, something like the gizmo's that prevent water hammer in plumbing pipes. Many fuel systems have these on the pressure side to reduce pressure waves and fuel noise. Even my '63 230SL has one. Except in this use the device has to work under vacuum rather than pressure. Also, I think that the pressure fluctuations are much greater and that might lead to a short life for the diaphragm.
That is why I'm leaning towards a larger and softer fuel line. The larger fuel line will introduce less resistance and the flex will help absorb the pulses.
There are more benefits than just getting the full power out of the engine. With no bubbles in the fuel, the timing is spot on and the spray pattern is better. Thus it smokes much less on hard acceleration and appears to get better mileage. I'm showing ~10% better, but need several more tank fills to prove that.
It would be really great if someone with an OM606 or OM605 could measure the diameter of the inlet to the fuel thermostat.
(08-22-2012, 04:57 AM)mantahead hi fuel thermostat is:
at top inside diameter 12mm
at side (where rubber pipe pushes on) inside diameter 6.8mm
Although it is 12mm the inside diameter of the pipe going on there is 6mm
Thanks!
So to be sure, the outside diameter of the hose nipple is 12mm and the inside is 6.8? 12mm seems a bit large, only because I managed to force an 8mm hose over it, all be it with a lot of grunting & swearing. Is that measured at the thickest or thinnest part of the nipple? The measurement that matters most is the diameter of the straight section of the nipple where the hose clamp is applied.
...Alan
(08-22-2012, 04:57 AM)mantahead hi fuel thermostat is:
at top inside diameter 12mm
at side (where rubber pipe pushes on) inside diameter 6.8mm
Although it is 12mm the inside diameter of the pipe going on there is 6mm
Thanks!
So to be sure, the outside diameter of the hose nipple is 12mm and the inside is 6.8? 12mm seems a bit large, only because I managed to force an 8mm hose over it, all be it with a lot of grunting & swearing. Is that measured at the thickest or thinnest part of the nipple? The measurement that matters most is the diameter of the straight section of the nipple where the hose clamp is applied.
...Alan
(08-22-2012, 10:49 AM)AlanMcRhi,(08-22-2012, 04:57 AM)mantahead hi fuel thermostat is:
at top inside diameter 12mm
at side (where rubber pipe pushes on) inside diameter 6.8mm
Although it is 12mm the inside diameter of the pipe going on there is 6mm
Thanks!
So to be sure, the outside diameter of the hose nipple is 12mm and the inside is 6.8? 12mm seems a bit large, only because I managed to force an 8mm hose over it, all be it with a lot of grunting & swearing. Is that measured at the thickest or thinnest part of the nipple? The measurement that matters most is the diameter of the straight section of the nipple where the hose clamp is applied.
...Alan
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
(08-22-2012, 10:49 AM)AlanMcRhi,(08-22-2012, 04:57 AM)mantahead hi fuel thermostat is:
at top inside diameter 12mm
at side (where rubber pipe pushes on) inside diameter 6.8mm
Although it is 12mm the inside diameter of the pipe going on there is 6mm
Thanks!
So to be sure, the outside diameter of the hose nipple is 12mm and the inside is 6.8? 12mm seems a bit large, only because I managed to force an 8mm hose over it, all be it with a lot of grunting & swearing. Is that measured at the thickest or thinnest part of the nipple? The measurement that matters most is the diameter of the straight section of the nipple where the hose clamp is applied.
...Alan
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
(08-22-2012, 12:04 PM)mantahead hi,
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
Excellent! I just dug up a picture off for the benefit of anyone reading this thread later.
i was talking to a parts man in a Mercedes dealership today about this issue and he told me:
over the years they had some problems with air bubbles in the fuel lines and some cars where hard to start if left overnight but they drove alright. Nine times out of ten the problem was the o ring behind the electric cut off valve on the side of the pump.
Almost forgot, on a few rare occasions some cars still had problems and there was a kit available which had some sort of pipe re-routing or something in it.
hi,
i was talking to a parts man in a Mercedes dealership today about this issue and he told me:
over the years they had some problems with air bubbles in the fuel lines and some cars where hard to start if left overnight but they drove alright. Nine times out of ten the problem was the o ring behind the electric cut off valve on the side of the pump.
Almost forgot, on a few rare occasions some cars still had problems and there was a kit available which had some sort of pipe re-routing or something in it.
(08-22-2012, 03:44 PM)mantahead hi,
i was talking to a parts man in a Mercedes dealership today about this issue and he told me:
over the years they had some problems with air bubbles in the fuel lines and some cars where hard to start if left overnight but they drove alright. Nine times out of ten the problem was the o ring behind the electric cut off valve on the side of the pump.
Almost forgot, on a few rare occasions some cars still had problems and there was a kit available which had some sort of pipe re-routing or something in it.
The kit would be interesting to hear about.
Yeah, everyone who has had an OM606 or OM605 for any length of time has experienced the leaky o-rings. It is a terrible design, especially when the pipes are under the intake manifold like that. The one behind the SOV is the one that most people miss. Usually those o-rings result in air creeping in with the engine off. I've replaced all of them more than once on both the E & the G. The Viton rings do seem to last much longer.
Still, I had "air bubbles" in the lines even after the fix. As stated in the long monolog, those bubbles were in fact not air but diesel vapors, vaguely analogous to vapor lock on a gas engine, but smaller bubbles and different cause.
(08-22-2012, 03:44 PM)mantahead hi,
i was talking to a parts man in a Mercedes dealership today about this issue and he told me:
over the years they had some problems with air bubbles in the fuel lines and some cars where hard to start if left overnight but they drove alright. Nine times out of ten the problem was the o ring behind the electric cut off valve on the side of the pump.
Almost forgot, on a few rare occasions some cars still had problems and there was a kit available which had some sort of pipe re-routing or something in it.
The kit would be interesting to hear about.
Yeah, everyone who has had an OM606 or OM605 for any length of time has experienced the leaky o-rings. It is a terrible design, especially when the pipes are under the intake manifold like that. The one behind the SOV is the one that most people miss. Usually those o-rings result in air creeping in with the engine off. I've replaced all of them more than once on both the E & the G. The Viton rings do seem to last much longer.
Still, I had "air bubbles" in the lines even after the fix. As stated in the long monolog, those bubbles were in fact not air but diesel vapors, vaguely analogous to vapor lock on a gas engine, but smaller bubbles and different cause.
Hope you dont mind, Ive copied this post onto a UK Veg-oil forum, where there's always someone bleating about air in fuel issues-(issue will be MUCH worse with thicker fuel, maybe with solvents added)
--Full credit to yourself and a link back to this thread here.
Here is the thread I started there--
http://www.vegetableoildiesel.co.uk/foru...?tid=33094
![[Image: 300TDnoplate.jpg]](http://i190.photobucket.com/albums/z128/alastairhcii/300TDnoplate.jpg)
Alastair E
08-25-2012, 05:21 PM #13AlanMcR--
Hope you dont mind, Ive copied this post onto a UK Veg-oil forum, where there's always someone bleating about air in fuel issues-(issue will be MUCH worse with thicker fuel, maybe with solvents added)
--Full credit to yourself and a link back to this thread here.
Here is the thread I started there--
http://www.vegetableoildiesel.co.uk/foru...?tid=33094
(08-25-2012, 05:21 PM)Alastair E AlanMcR--
Hope you dont mind, Ive copied this post onto a UK Veg-oil forum, where there's always someone bleating about air in fuel issues-(issue will be MUCH worse with thicker fuel, maybe with solvents added)
--Full credit to yourself and a link back to this thread here.
Here is the thread I started there--
http://www.vegetableoildiesel.co.uk/foru...?tid=33094
No problem at all, I posted this in the hopes that it would help others. You might want to edit out the last paragraph, as I've gotten confirmation that the fuel thermostat inlet is 10mm (roughly 3/8" for us in the US that have a tough time getting metric hose).
(08-25-2012, 05:21 PM)Alastair E AlanMcR--
Hope you dont mind, Ive copied this post onto a UK Veg-oil forum, where there's always someone bleating about air in fuel issues-(issue will be MUCH worse with thicker fuel, maybe with solvents added)
--Full credit to yourself and a link back to this thread here.
Here is the thread I started there--
http://www.vegetableoildiesel.co.uk/foru...?tid=33094
No problem at all, I posted this in the hopes that it would help others. You might want to edit out the last paragraph, as I've gotten confirmation that the fuel thermostat inlet is 10mm (roughly 3/8" for us in the US that have a tough time getting metric hose).
Yep i have one 605 N/A and all of a sudden the engine ceased to deliver normal power especially during climbs, in flat roads still goes to 160/170/ km. The thing is that the fuel system is very far from what it was standard. First deleted the fuel heater exchanger, after had a clog on the fuel tank lines , well O rings never replaced them, usually the fuel is a mix of waste engine oil and diesel half by half.
Noticeable differences is that the engine heats up to much from what it did. even in flat roads i have to switch on the E fan, started to smoke white when cold, and smoking a lot at high rev´s. something it didn´t. and of course does not start as fast as it did.
In the beginning i thought it was wear due to this fuel mix but after i analyze some surfaces and the mix (microscopic analysis) and found no reason or sign of wear.
It could be a lot of things, in almost 100.000 km i never checked chain stretch or wear, never checked IP timing (for the new fuel mix). sometimes it behaves like the fuel filter is clogged.
My bet is for troubles in the fuel system, does anyone of u know which is min pressure at IP inlet, and what min pressure should the lift pump build?
BTW anyone know where to find maintenance procedure for chain stretch, and timing in 605.
Thanks in advance
FD,
Powered by tractor fuel
Hello fine people,
Yep i have one 605 N/A and all of a sudden the engine ceased to deliver normal power especially during climbs, in flat roads still goes to 160/170/ km. The thing is that the fuel system is very far from what it was standard. First deleted the fuel heater exchanger, after had a clog on the fuel tank lines , well O rings never replaced them, usually the fuel is a mix of waste engine oil and diesel half by half.
Noticeable differences is that the engine heats up to much from what it did. even in flat roads i have to switch on the E fan, started to smoke white when cold, and smoking a lot at high rev´s. something it didn´t. and of course does not start as fast as it did.
In the beginning i thought it was wear due to this fuel mix but after i analyze some surfaces and the mix (microscopic analysis) and found no reason or sign of wear.
It could be a lot of things, in almost 100.000 km i never checked chain stretch or wear, never checked IP timing (for the new fuel mix). sometimes it behaves like the fuel filter is clogged.
My bet is for troubles in the fuel system, does anyone of u know which is min pressure at IP inlet, and what min pressure should the lift pump build?
BTW anyone know where to find maintenance procedure for chain stretch, and timing in 605.
Thanks in advance
FD,
Powered by tractor fuel
(08-22-2012, 01:37 PM)AlanMcR(08-22-2012, 12:04 PM)mantahead hi,
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
Excellent! I just dug up a picture off for the benefit of anyone reading this thread later.
I have bypassed that bugger on my om606 G wagon,460.No more air in my fuel lines also they have been replaced with 8 mm new hoses from the tank to lift pump.Another good idea is to remove all O ring plastic lines with rubber ones attached to Stainless Steel Hose Nipple.This way I got only 2 rubber O rings left on my fuel system:1 on the fuel filter and 2 behind the shut off valve.In order to heat the fuel I have installed heat exchanger.
![[Image: BSPT-NPT-DIN-Stainless-Steel-Hose-Nipple-HON-.jpg]](http://image.made-in-china.com/4f0j00LvRafCJYJipM/BSPT-NPT-DIN-Stainless-Steel-Hose-Nipple-HON-.jpg)
(08-22-2012, 01:37 PM)AlanMcR(08-22-2012, 12:04 PM)mantahead hi,
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
Excellent! I just dug up a picture off for the benefit of anyone reading this thread later.
I have bypassed that bugger on my om606 G wagon,460.No more air in my fuel lines also they have been replaced with 8 mm new hoses from the tank to lift pump.Another good idea is to remove all O ring plastic lines with rubber ones attached to Stainless Steel Hose Nipple.This way I got only 2 rubber O rings left on my fuel system:1 on the fuel filter and 2 behind the shut off valve.In order to heat the fuel I have installed heat exchanger.
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
hi,
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
(08-26-2012, 02:36 AM)TURBO_DAN I have bypassed that bugger on my om606 G wagon,460.No more air in my fuel lines also they have been replaced with 8 mm new hoses from the tank to lift pump.Another good idea is to remove all O ring plastic lines with rubber ones attached to Stainless Steel Hose Nipple.This way I got only 2 rubber O rings left on my fuel system:1 on the fuel filter and 2 behind the shut off valve.In order to heat the fuel I have installed heat exchanger.
I've contemplated this several times. What is the threading that you used? Any drawbacks to this modification that you've discovered?
(08-26-2012, 05:01 PM)mantahead hi,From a performance perspective this setup is good. What pressure does the system achieve at the IP? One possible modification is to install a smaller orifice in the overflow return valve. Mine "leaks" 1L/m back to the tank for cooling purposes.
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
From my reading, you have largely rigid (nylon) pipe in the fuel supply. You might want to include a section of flexible hose to absorb the pulses caused by the IP.
I've decided that I don't want to rely on an electric pump, simply for back-woods reliability.
(08-26-2012, 02:36 AM)TURBO_DAN I have bypassed that bugger on my om606 G wagon,460.No more air in my fuel lines also they have been replaced with 8 mm new hoses from the tank to lift pump.Another good idea is to remove all O ring plastic lines with rubber ones attached to Stainless Steel Hose Nipple.This way I got only 2 rubber O rings left on my fuel system:1 on the fuel filter and 2 behind the shut off valve.In order to heat the fuel I have installed heat exchanger.
I've contemplated this several times. What is the threading that you used? Any drawbacks to this modification that you've discovered?
(08-26-2012, 05:01 PM)mantahead hi,From a performance perspective this setup is good. What pressure does the system achieve at the IP? One possible modification is to install a smaller orifice in the overflow return valve. Mine "leaks" 1L/m back to the tank for cooling purposes.
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
From my reading, you have largely rigid (nylon) pipe in the fuel supply. You might want to include a section of flexible hose to absorb the pulses caused by the IP.
I've decided that I don't want to rely on an electric pump, simply for back-woods reliability.
(08-26-2012, 05:01 PM)mantahead hi,
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
What pump was used? Is it regulated,what pressure?
Just trying to catch -up. Thanks.
(08-26-2012, 05:01 PM)mantahead hi,
on my om605 drift car i used, electric inline pump near the tank which fed a twin filter housing of a renault truck. So, original lift pump and filter where taken off. Pipes where changed to 12mm nylon right to the tank.
I had nowhere to put the injector leak offs so i used a return banjo off a bmw 325tds which had the small fitting for the leak offs. This banjo was fitted to the return on the pump.
I was wondering, could i do anything to improve this setup?
What pump was used? Is it regulated,what pressure?
Just trying to catch -up. Thanks.
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
Hi,
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
it was 2bar at idle and then it would drop back under full load, can't remember exact pressure, i think a rising rate regulator would be best that increases with boost pressure, what you think?
(08-31-2012, 05:28 AM)tomnik Hi,
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
hi,
it was 2bar at idle and then it would drop back under full load, can't remember exact pressure, i think a rising rate regulator would be best that increases with boost pressure, what you think?
(08-31-2012, 05:28 AM)tomnik Hi,
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
no idea about the rising rate reg.
I mounted a lift pump off a MW pump (for the only reason that I like more the roller on the cam than the pin) and get 2.2 - 2.5 bar idle but then down to 1 bar at WOT with new filter and warm outside temperatures.
I don't feel this is too low pressure but on the other hand I never tried with 2 bar at WOT.
Tom
(08-31-2012, 07:05 AM)mantahead hi,
it was 2bar at idle and then it would drop back under full load, can't remember exact pressure, i think a rising rate regulator would be best that increases with boost pressure, what you think?
(08-31-2012, 05:28 AM)tomnik Hi,
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
Hi,
no idea about the rising rate reg.
I mounted a lift pump off a MW pump (for the only reason that I like more the roller on the cam than the pin) and get 2.2 - 2.5 bar idle but then down to 1 bar at WOT with new filter and warm outside temperatures.
I don't feel this is too low pressure but on the other hand I never tried with 2 bar at WOT.
Tom
(08-31-2012, 07:05 AM)mantahead hi,
it was 2bar at idle and then it would drop back under full load, can't remember exact pressure, i think a rising rate regulator would be best that increases with boost pressure, what you think?
(08-31-2012, 05:28 AM)tomnik Hi,
is this 2 bar under load or at idle/low load?
What is the pressure with WOT?
Tom
(08-28-2012, 07:55 AM)mantahead hi,
i have 2bar entering the ip.
Dont know the make of the pump, think its off a petrol fuel injected car.
The pressure is just regulated by the return banjo bolt.
One thing is for sure, it is so much easier to bleed the fuel system with electric pump feeding the ip.
When my mechanic removed the drain plug under the fuel tank, fuel would flow out even though the tank had more than 30 liters in.
Nasty stuff.
1992 Mercedes 190D 2.5 turbo 5sp manual. EGT+boost gauges. Boost controller set to ~14.5 psi. 1 1/4 turns on full load adjustment. LPG injection.
![[Image: 3803751914_8fdca63138_o.jpg]](http://farm4.static.flickr.com/3543/3803751914_8fdca63138_o.jpg)
I would also check the filter screen in the tank. I used fresh vegie oil for some time and it plugged the filter scree in the tank.
When my mechanic removed the drain plug under the fuel tank, fuel would flow out even though the tank had more than 30 liters in.
Nasty stuff.
1992 Mercedes 190D 2.5 turbo 5sp manual. EGT+boost gauges. Boost controller set to ~14.5 psi. 1 1/4 turns on full load adjustment. LPG injection.
Newbie-read this: Cheap Tricks
617.952-220k-Getting built up
larsalan I guess I need to look at this stupid ass drip shit. What you have to like mess with those elements on the pump? What a fucking hassle. then use some wire to hold the throttle open or some shit?
Simpler=Better
08-31-2012, 02:15 PM #25Cigar hose? What about a mini tank under the hood?
Newbie-read this: Cheap Tricks
617.952-220k-Getting built up
larsalan I guess I need to look at this stupid ass drip shit. What you have to like mess with those elements on the pump? What a fucking hassle. then use some wire to hold the throttle open or some shit?
Rising rate regulator wont work in this case. If its unregulated and still drops at WOT then you are exceeding the amount the pump can supply so the pressure is dropping. If you were to put a bigger higher flow pump in then yes a regulator would hold the pressure that you set it at. Rising rate is pointless in a diesel though. They are used in turbo petrol cars to overcome the increase in pressure at the injector due to higher boost. If your supplying 1bar fuel pressure and using 1 bar boost then no fuel would be injected because the pressures are equal. On a diesel though you are only supplying another high pressure pump so boost pressure doesn't affect it in any way.
Can someone help me out im looking for an electronic fuel pump for my 603 and i dont want to get the wrong one. Can someone tell what electronic fuel pump you use or where to get one? thanks. and the fuel filter does that need to be changed to an aftermarket one? like a higher flowing fuel filter?
(08-22-2012, 01:37 PM)AlanMcR(08-22-2012, 12:04 PM)mantahead hi,
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
Excellent! I just dug up a picture off for the benefit of anyone reading this thread later.
The inside of the thermostat fuel path is very small in it.
I opened mine long ago and there is a lot of restriction in it.
Olivier
(08-22-2012, 01:37 PM)AlanMcR(08-22-2012, 12:04 PM)mantahead hi,
no the one with the rubber hose is 10mm or 10.8mm at thickest point outside diameter.
the 12mm is the inside diameter of the other pipe with the plastic fitting.
Excellent! I just dug up a picture off for the benefit of anyone reading this thread later.
The inside of the thermostat fuel path is very small in it.
I opened mine long ago and there is a lot of restriction in it.
Olivier
I was thinking about pulling a vacuum on some fuel but instead did something better and googled the subject. I found a cool short .pdf on the "Phenomena of Air Separation in Diesel Fuel". This should further the conversation since it differentiates between entrapped air and fuel vapor.
http://www.parker.com/literature/Racor/M...l_Fuel.pdf
raysorenson
10-20-2012, 01:47 PM #29Wonderful thread. I skipped over it before because the title seemed 606 specific... I need to stop judging books by their covers.
I was thinking about pulling a vacuum on some fuel but instead did something better and googled the subject. I found a cool short .pdf on the "Phenomena of Air Separation in Diesel Fuel". This should further the conversation since it differentiates between entrapped air and fuel vapor.
http://www.parker.com/literature/Racor/M...l_Fuel.pdf
hansebanger77
10-25-2012, 01:23 PM #30Nice tread. I also Running Out of fuel since i adjust my Pump for more power. 606 na now with Little Turbo :-) i Bypass ? Avoid? The Thermostat but Nothing Happens better. So im waiting for next week for my harder spring and overflow valve same as i do it in my superturbo. And see what happens. Why I get in my 91 superturbo over 400 hp with stock line from the tank and in my other 93 not enough for about 150-160hp I think. Hmm
Cheers.
I have installed a non return valve on the Return, on the filter head, it help a bit as its a little restriction and the fuel stay a wee more under pressure as its recirculated back in the pump, I thought I may add this too
On the 606 W210 there is a big restriction on the filter head, right after the pre-filter. I think it go down to 6mm there. I drilled mine long ago on the first E to get better flow.
Is it a EDC 606 pump you are using Hansebanger? If yes, what valve did you use?
Cheers.
I have installed a non return valve on the Return, on the filter head, it help a bit as its a little restriction and the fuel stay a wee more under pressure as its recirculated back in the pump, I thought I may add this too
On the 606 W210 there is a big restriction on the filter head, right after the pre-filter. I think it go down to 6mm there. I drilled mine long ago on the first E to get better flow.
(10-25-2012, 01:41 PM)Olivier Is it a EDC 606 pump you are using Hansebanger? If yes, what valve did you use?
Cheers.
I have installed a non return valve on the Return, on the filter head, it help a bit as its a little restriction and the fuel stay a wee more under pressure as its recirculated back in the pump, I thought I may add this too
On the 606 W210 there is a big restriction on the filter head, right after the pre-filter. I think it go down to 6mm there. I drilled mine long ago on the first E to get better flow.
No the NA 606 in w124 is mechanic no edc. The Tuning valve Open later at higher pressure and helps to get more internal fuel pressure in the pump. Also the harder spring in the pump. In my superturbo the combination work really nice. Maybe the edc have the same? The valve is on the backside of the pump between engine and pump in the return hose ;-)
hansebanger77
10-25-2012, 02:15 PM #32(10-25-2012, 01:41 PM)Olivier Is it a EDC 606 pump you are using Hansebanger? If yes, what valve did you use?
Cheers.
I have installed a non return valve on the Return, on the filter head, it help a bit as its a little restriction and the fuel stay a wee more under pressure as its recirculated back in the pump, I thought I may add this too
On the 606 W210 there is a big restriction on the filter head, right after the pre-filter. I think it go down to 6mm there. I drilled mine long ago on the first E to get better flow.
No the NA 606 in w124 is mechanic no edc. The Tuning valve Open later at higher pressure and helps to get more internal fuel pressure in the pump. Also the harder spring in the pump. In my superturbo the combination work really nice. Maybe the edc have the same? The valve is on the backside of the pump between engine and pump in the return hose ;-)
I know the valve, I have dismantled one previously, on the EDC pump there is really little pressure on the teeny teeny spring and the inside it also made of plastic...
There was another valve we could used and that you could open and stretch the spring, it was on peachparts, but I can't remenber from which car it was
Waiting on Alastair to tell me if he remeber
here is the valve open, check post 406 and 407
http://www.peachparts.com/shopforum/dies...nt-28.html
It seems the valve from a 123 would fit, but that was never really confirmed
Cheers
I know the valve, I have dismantled one previously, on the EDC pump there is really little pressure on the teeny teeny spring and the inside it also made of plastic...
There was another valve we could used and that you could open and stretch the spring, it was on peachparts, but I can't remenber from which car it was
Waiting on Alastair to tell me if he remeber
here is the valve open, check post 406 and 407
http://www.peachparts.com/shopforum/dies...nt-28.html
It seems the valve from a 123 would fit, but that was never really confirmed
Not want to contradict anyone here is one very interesting fact. As i explain in a thread before my 124 with 605 engine was with some power problems and i suspected fuel supply, well it was and it was not.
So back to my garage and installed one of this BMW aftermarket all model electric fuel pump just after the tank, one 8 mm(inside) hose , those plastic ones used for air compressors, leads the fuel directly to the filter housing. The rest of the installation remains the same.(as it was from factory)
Installed a safety switch to kill the pump if needed. Normally the pump is switched when the ignition is turned for start.
The pump was said to supply fuel at 5 bar , maybe it is, what i can tell u is that the hose handles 10 bar and it swell when at idle. At WOT maintain the same swell. don´t ask me about the pressure cause i have no idea.
Some of my problems disappeared, but what was remarkable is that i eliminated the lift pump and guess?? with the electric pump off the IP is able to suck the fuel from the tank, start the engine, no noticeable differences when running, well when i need some torque there is some difference, less power available, engine is able to rev at 6k just with the IP sucking fuel. My engine has made a lot of KM on highway at 5.5 k and even 6K. maybe that's why is loosing power.
(this fuel pump i bough has no restrictions inside, so must be below the tank)
When i got some time i come with the pic´s.
Regards to u all
FD,
Powered by tractor fuel
Hello fine people,
Not want to contradict anyone here is one very interesting fact. As i explain in a thread before my 124 with 605 engine was with some power problems and i suspected fuel supply, well it was and it was not.
So back to my garage and installed one of this BMW aftermarket all model electric fuel pump just after the tank, one 8 mm(inside) hose , those plastic ones used for air compressors, leads the fuel directly to the filter housing. The rest of the installation remains the same.(as it was from factory)
Installed a safety switch to kill the pump if needed. Normally the pump is switched when the ignition is turned for start.
The pump was said to supply fuel at 5 bar , maybe it is, what i can tell u is that the hose handles 10 bar and it swell when at idle. At WOT maintain the same swell. don´t ask me about the pressure cause i have no idea.
Some of my problems disappeared, but what was remarkable is that i eliminated the lift pump and guess?? with the electric pump off the IP is able to suck the fuel from the tank, start the engine, no noticeable differences when running, well when i need some torque there is some difference, less power available, engine is able to rev at 6k just with the IP sucking fuel. My engine has made a lot of KM on highway at 5.5 k and even 6K. maybe that's why is loosing power.
(this fuel pump i bough has no restrictions inside, so must be below the tank)
When i got some time i come with the pic´s.
Regards to u all
FD,
Powered by tractor fuel
(08-21-2012, 12:33 PM)AlanMcR I thought I'd post some things I've discovered about the OM606 fuel system. You folks are always interested in performance issues and this is a basic design flaw in the MB implementation. While this is a bit of an oddball case (OM606 in a G-wagen - WDB46333117106xxx), the issues also apply to the OM606 in the E-class and probably in the S-class, too. The underlying issues are probably applicable to a wide range of inline IP pump diesels.
What got me going on this was the the engine had poor power and ran just a little rough past about 2800rpm. There was one exception though, and that was when the fuel tank was full, right up to the lip. The other clue was that one could see bubbles in the clear fuel lines whenever the engine was revved up (out of gear).
The answer is that A) the fuel system was poorly designed (by Bosch); and, B) not even built (by MB) the way it was designed. This gets to be a long story, but the basic problem is that the lift pump pulls so hard that it pulls gasses out of the diesel fuel on its intake stroke. Those gasses do not diffuse back into the fuel during the delivery stroke (basic physics). Once the bubbles form, they are in the system for a long time. This is because getting gasses out of solution is much easier (and faster) than diffusing a large bubble back in to the solution. The bubbles are large in the line before the fine fuel filter and get chopped into 10 micron bubbles by the filter. The tiny bubbles are harder to see, but they are still gas bubbles and haven’t recombined into the liquid. Since they are compressible, when the IP plunger starts delivering fuel it first has to compress the bubbles to the injector opening pressure, that introduces a delay in timing. Also, since part of the chamber was filled with gas, that effectively reduces the total fuel delivery. Both problems reduce power.
Background: The diagnosis took a while. As I said earlier, I’ve noticed bubbles in the line going to the fine fuel filter at elevated RPM’s. I always assumed that the problem was due to air sneaking past the o-rings. I believed this even though the leaks continued with fresh o-rings. How wrong I was.
Recently, while doing some work with the intake manifold off, I decided to run an experiment. I installed some clear soft 8mm Tygothane tubing in place of the line going from the tank to the fuel heater/thermostat. There were no bubbles in the line. In fact there were no bubbles anywhere in the system. Aha! I said. The fuel line must have been leaky. I did notice that the soft clear line was pulsating wildly with each stroke of the lift pump. Just for fun I squeezed the line with my fingers to see if that would kill the engine. As I started to squeeze the line, a foam of bubbles appeared in the flow just after the pinch spot. Clearly the tube wasn’t leaking. Rather, the suction of the pump was lowering the tube pressure below the vapor pressure of diesel fuel. Thinking about this more, I realized that the reason that the bubbles had disappeared was because the pulsating line was providing pressure stabilization. So, the conclusion is that pressure (or rather vacuum) pulses are the cause of the bubbles.
Now for the design mistakes. The OM606 has no hand primer. Bosch needed a way to self-prime the system before the battery died. They chose to increase the volume of the lift pump and re-design the overflow return valve. In the past, the valve was designed to maintain a minimum pressure in the IP. In order to self-prime, the OM606 valve was re-designed as a simple one-way valve with a rather large opening. It prevents fuel from flowing backwards, but provides little flow restriction. The pump and valve together can move a lot of fuel, more fuel than the old fuel lines were designed for.
“No problem”, the Bosch engineers said, “we’ll just make the fuel line bigger”. They made the inlet to the fuel thermostat ~10mm rather than the old 8mm. The larger pipe will flow 56% more fuel. What could go wrong? Well, the MB bean-counters got in there and managed to make it go wrong. To save money, they installed an 8mm hose with a ~10mm bulge at the end. Worse, they connected this to a thick walled fuel line that is <6mm in the inside and almost 3M long. The steel line only flows ~36% of the intended Bosch design. That restriction is enough to ensure massive pressure pulses. Ooops.
Technically, a 6mm ID tube would flow the required 3lpm. But only if that flow were smooth. Unfortunately the flow is driven by a piston pump at 1/2 RPM and it is definitely not smooth. It is the pulses that cause the vacuum and thus the bubbles.
This design is present on the E and G. The problem is made worse on the G, because the fuel needs to be lifted up ~20cm, even on flat ground. The G always ran better if I filled the G up all the way to the edge of the opening. After the first liter was burned off, performance returned to “normal”. The extra performance was because fuel was being pushed into the fuel line, rather than pulled. On a steep upslope this is, of course, even worse.
At altitude there is another phenomenon. Since the fuel system is a suction system, the only reason that fuel flows is because the pump inlet is at a lower pressure than the tank. From a basic physics perspective, air pressure in the tank is pushing the fuel into the lift pump. As you go higher there is less and less air pressure pushing on the fuel. So, all the problems listed above just get worse. On my G the problem can be severe at >3000M. With a low tank at 4000M the fuel line is full of bubbles and it hardly moves at all.
Simply because I had it handy, I installed a long 8mm hose all the way to the tank, eliminating the steel line. This noticeably improved the performance, particularly in uphill passing.
Request: Does someone have a OM606 fuel thermostat in hand? I'd like a verification of the inlet neck measurement. I recall 10mm, but it might have been 1mm larger or smaller. I don’t want to take off the manifold just to measure that. I need the measurement at the neck not the bead.
Austincarnut
10-31-2012, 08:45 PM #35That is why you can't buy a pushrod type lift pump for a 12 valve dodge at the dealer any more. The suck lift pumps are problematic if you have the slightest air leak. All lift pumps sold are in-tank push pumps w/ regulators like everything else nowadays.
(08-21-2012, 12:33 PM)AlanMcR I thought I'd post some things I've discovered about the OM606 fuel system. You folks are always interested in performance issues and this is a basic design flaw in the MB implementation. While this is a bit of an oddball case (OM606 in a G-wagen - WDB46333117106xxx), the issues also apply to the OM606 in the E-class and probably in the S-class, too. The underlying issues are probably applicable to a wide range of inline IP pump diesels.
What got me going on this was the the engine had poor power and ran just a little rough past about 2800rpm. There was one exception though, and that was when the fuel tank was full, right up to the lip. The other clue was that one could see bubbles in the clear fuel lines whenever the engine was revved up (out of gear).
The answer is that A) the fuel system was poorly designed (by Bosch); and, B) not even built (by MB) the way it was designed. This gets to be a long story, but the basic problem is that the lift pump pulls so hard that it pulls gasses out of the diesel fuel on its intake stroke. Those gasses do not diffuse back into the fuel during the delivery stroke (basic physics). Once the bubbles form, they are in the system for a long time. This is because getting gasses out of solution is much easier (and faster) than diffusing a large bubble back in to the solution. The bubbles are large in the line before the fine fuel filter and get chopped into 10 micron bubbles by the filter. The tiny bubbles are harder to see, but they are still gas bubbles and haven’t recombined into the liquid. Since they are compressible, when the IP plunger starts delivering fuel it first has to compress the bubbles to the injector opening pressure, that introduces a delay in timing. Also, since part of the chamber was filled with gas, that effectively reduces the total fuel delivery. Both problems reduce power.
Background: The diagnosis took a while. As I said earlier, I’ve noticed bubbles in the line going to the fine fuel filter at elevated RPM’s. I always assumed that the problem was due to air sneaking past the o-rings. I believed this even though the leaks continued with fresh o-rings. How wrong I was.
Recently, while doing some work with the intake manifold off, I decided to run an experiment. I installed some clear soft 8mm Tygothane tubing in place of the line going from the tank to the fuel heater/thermostat. There were no bubbles in the line. In fact there were no bubbles anywhere in the system. Aha! I said. The fuel line must have been leaky. I did notice that the soft clear line was pulsating wildly with each stroke of the lift pump. Just for fun I squeezed the line with my fingers to see if that would kill the engine. As I started to squeeze the line, a foam of bubbles appeared in the flow just after the pinch spot. Clearly the tube wasn’t leaking. Rather, the suction of the pump was lowering the tube pressure below the vapor pressure of diesel fuel. Thinking about this more, I realized that the reason that the bubbles had disappeared was because the pulsating line was providing pressure stabilization. So, the conclusion is that pressure (or rather vacuum) pulses are the cause of the bubbles.
Now for the design mistakes. The OM606 has no hand primer. Bosch needed a way to self-prime the system before the battery died. They chose to increase the volume of the lift pump and re-design the overflow return valve. In the past, the valve was designed to maintain a minimum pressure in the IP. In order to self-prime, the OM606 valve was re-designed as a simple one-way valve with a rather large opening. It prevents fuel from flowing backwards, but provides little flow restriction. The pump and valve together can move a lot of fuel, more fuel than the old fuel lines were designed for.
“No problem”, the Bosch engineers said, “we’ll just make the fuel line bigger”. They made the inlet to the fuel thermostat ~10mm rather than the old 8mm. The larger pipe will flow 56% more fuel. What could go wrong? Well, the MB bean-counters got in there and managed to make it go wrong. To save money, they installed an 8mm hose with a ~10mm bulge at the end. Worse, they connected this to a thick walled fuel line that is <6mm in the inside and almost 3M long. The steel line only flows ~36% of the intended Bosch design. That restriction is enough to ensure massive pressure pulses. Ooops.
Technically, a 6mm ID tube would flow the required 3lpm. But only if that flow were smooth. Unfortunately the flow is driven by a piston pump at 1/2 RPM and it is definitely not smooth. It is the pulses that cause the vacuum and thus the bubbles.
This design is present on the E and G. The problem is made worse on the G, because the fuel needs to be lifted up ~20cm, even on flat ground. The G always ran better if I filled the G up all the way to the edge of the opening. After the first liter was burned off, performance returned to “normal”. The extra performance was because fuel was being pushed into the fuel line, rather than pulled. On a steep upslope this is, of course, even worse.
At altitude there is another phenomenon. Since the fuel system is a suction system, the only reason that fuel flows is because the pump inlet is at a lower pressure than the tank. From a basic physics perspective, air pressure in the tank is pushing the fuel into the lift pump. As you go higher there is less and less air pressure pushing on the fuel. So, all the problems listed above just get worse. On my G the problem can be severe at >3000M. With a low tank at 4000M the fuel line is full of bubbles and it hardly moves at all.
Simply because I had it handy, I installed a long 8mm hose all the way to the tank, eliminating the steel line. This noticeably improved the performance, particularly in uphill passing.
Request: Does someone have a OM606 fuel thermostat in hand? I'd like a verification of the inlet neck measurement. I recall 10mm, but it might have been 1mm larger or smaller. I don’t want to take off the manifold just to measure that. I need the measurement at the neck not the bead.
basically took feed straight to lift pump then up to thermostat and back to the immobiliser valve then to filter (prefilter is bypassed)
problem is that this re-routing has resulted in the EPC light coming on with resultant power reduction as I believe it must cut turbo boost signal
I then connected another immobiliser valve I had as a slave to my existing electric socket with the same result, car starts and runs fine but as above EPC on and power reduction
can anyone shed any light on what it is thats throwing the code
my next option is to loop /blank 2 of the valve ports
yorkshire1
04-19-2014, 12:46 PM #36thought Id experiment with the OM605 electronic pump plumbing today by pressurizing rather than having the clear lines under vaccuum/ suction as Ive been having intermittent air ingress after throttling off then accelerating again
basically took feed straight to lift pump then up to thermostat and back to the immobiliser valve then to filter (prefilter is bypassed)
problem is that this re-routing has resulted in the EPC light coming on with resultant power reduction as I believe it must cut turbo boost signal
I then connected another immobiliser valve I had as a slave to my existing electric socket with the same result, car starts and runs fine but as above EPC on and power reduction
can anyone shed any light on what it is thats throwing the code
my next option is to loop /blank 2 of the valve ports
(04-19-2014, 12:46 PM)yorkshire1 thought Id experiment with the OM605 electronic pump plumbing today by pressurizing rather than having the clear lines under vaccuum/ suction as Ive been having intermittent air ingress after throttling off then accelerating again
basically took feed straight to lift pump then up to thermostat and back to the immobiliser valve then to filter (prefilter is bypassed)
problem is that this re-routing has resulted in the EPC light coming on with resultant power reduction as I believe it must cut turbo boost signal
I then connected another immobiliser valve I had as a slave to my existing electric socket with the same result, car starts and runs fine but as above EPC on and power reduction
can anyone shed any light on what it is thats throwing the code
my next option is to loop /blank 2 of the valve ports
having plumbed the solenoid valve back up under suction and EPC light now off again the only conclusion i can draw is that the valve is also monitoring fuel pressure as well as temp
yorkshire1
04-21-2014, 06:05 AM #37(04-19-2014, 12:46 PM)yorkshire1 thought Id experiment with the OM605 electronic pump plumbing today by pressurizing rather than having the clear lines under vaccuum/ suction as Ive been having intermittent air ingress after throttling off then accelerating again
basically took feed straight to lift pump then up to thermostat and back to the immobiliser valve then to filter (prefilter is bypassed)
problem is that this re-routing has resulted in the EPC light coming on with resultant power reduction as I believe it must cut turbo boost signal
I then connected another immobiliser valve I had as a slave to my existing electric socket with the same result, car starts and runs fine but as above EPC on and power reduction
can anyone shed any light on what it is thats throwing the code
my next option is to loop /blank 2 of the valve ports
having plumbed the solenoid valve back up under suction and EPC light now off again the only conclusion i can draw is that the valve is also monitoring fuel pressure as well as temp
I have my fuel plumbed from the tank through a Lucas.CAV primary filter/ priming pump on the inner wing then to the lift pump then to the OE filter then to the IP. I cut out the thermostat heater thingy and the OE primary filter which doesn't seem to have any negative effect on the fuelling.
(04-21-2014, 06:16 AM)Druk I have my fuel plumbed from the tank through a Lucas.CAV primary filter/ priming pump on the inner wing then to the lift pump then to the OE filter then to the IP. I cut out the thermostat heater thingy and the OE primary filter which doesn't seem to have any negative effect on the fuelling.
mine has the prefilter bypassed also and have a 6 inch prefilter before the lift pump I run vegoil/petrol mix which exacerbates the already underspecced feed line from the tank as per the OP really I should fit a vaccuum guage to monitor feed
Ill now run bigger bore pipework from the tank
Itd be interesting to know what the solenoid valve on the side of IP actually monitors I know its function is part of the immobilizer system and as a failsafe fuel shut off device in case the main rack engine stop fails but why it would be pressure sensitive makes me wonder
yorkshire1
04-21-2014, 07:42 AM #39(04-21-2014, 06:16 AM)Druk I have my fuel plumbed from the tank through a Lucas.CAV primary filter/ priming pump on the inner wing then to the lift pump then to the OE filter then to the IP. I cut out the thermostat heater thingy and the OE primary filter which doesn't seem to have any negative effect on the fuelling.
mine has the prefilter bypassed also and have a 6 inch prefilter before the lift pump I run vegoil/petrol mix which exacerbates the already underspecced feed line from the tank as per the OP really I should fit a vaccuum guage to monitor feed
Ill now run bigger bore pipework from the tank
Itd be interesting to know what the solenoid valve on the side of IP actually monitors I know its function is part of the immobilizer system and as a failsafe fuel shut off device in case the main rack engine stop fails but why it would be pressure sensitive makes me wonder
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
yorkshire1
04-27-2014, 06:16 AM #41(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
(04-27-2014, 06:16 AM)yorkshire1(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
Having cut one open, I can assure you that is all that it does.
(04-27-2014, 06:16 AM)yorkshire1(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
Having cut one open, I can assure you that is all that it does.
(04-27-2014, 09:42 AM)AlanMcR(04-27-2014, 06:16 AM)yorkshire1(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
Having cut one open, I can assure you that is all that it does.
it begs the question what it is about that valve thats putting the epc light on then as the only difference is that its under pressure and not suction
yorkshire1
04-27-2014, 02:13 PM #43(04-27-2014, 09:42 AM)AlanMcR(04-27-2014, 06:16 AM)yorkshire1(04-25-2014, 06:56 PM)AlanMcR The immobilizer solenoid has two jobs.
1) it cuts off fuel flow
2) it measures fuel temperature.
If you disconnect it then the ECU will get unhappy. If you connect it, but leave it hanging in the engine compartment without fuel flow, then it will probably be upset by the measured fuel temperature being wrong.
appreciated they are its recognized functions however it seems its also pressure sensitive as it lights the EPC light if fed from the lift pump
Having cut one open, I can assure you that is all that it does.
it begs the question what it is about that valve thats putting the epc light on then as the only difference is that its under pressure and not suction
(04-27-2014, 02:13 PM)yorkshire1The design of the shutoff valve may be dependent on the inlet not being pressurized. Exactly how it shut off fuel wasn't clear to me (whether it cut off the inlet or the pressurized side). I might still have the autopsy victim in my garage. If so, I'll take a look at it.(04-27-2014, 09:42 AM)AlanMcR it begs the question what it is about that valve thats putting the epc light on then as the only difference is that its under pressure and not suction
I do plan on adding an electric lift pump. I hope I don't run into the same problems. Frankly, I was mulling over the idea of throwing the SOV away and tapping that spot for a simple hose from the filter.
(04-27-2014, 02:13 PM)yorkshire1The design of the shutoff valve may be dependent on the inlet not being pressurized. Exactly how it shut off fuel wasn't clear to me (whether it cut off the inlet or the pressurized side). I might still have the autopsy victim in my garage. If so, I'll take a look at it.(04-27-2014, 09:42 AM)AlanMcR it begs the question what it is about that valve thats putting the epc light on then as the only difference is that its under pressure and not suction
I do plan on adding an electric lift pump. I hope I don't run into the same problems. Frankly, I was mulling over the idea of throwing the SOV away and tapping that spot for a simple hose from the filter.
Like you I studied a cross sectional diagram of the valve but couldnt really make out the fuel pathways or how the spring loaded ball valves worked nor whether it was possible to cross contaminate dirty fuel into the IP on switch off with pressure feeding
One other thing that pressure feeding the valve caused was for the engine to run on for 3-4 seconds after key off which was interesting as rack off should be instantaneous so whether it was messing with ecu signals I know not!!
yorkshire1
05-07-2014, 07:50 AM #45yes simple = better with this plumbing however there would still be the issue of fooling the ecu/rewriting software to eliminate the valve
Like you I studied a cross sectional diagram of the valve but couldnt really make out the fuel pathways or how the spring loaded ball valves worked nor whether it was possible to cross contaminate dirty fuel into the IP on switch off with pressure feeding
One other thing that pressure feeding the valve caused was for the engine to run on for 3-4 seconds after key off which was interesting as rack off should be instantaneous so whether it was messing with ecu signals I know not!!
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