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+--- Thread: Startproblems in colder temperatures with a OM617A (/showthread.php?tid=5121)
Startproblems in colder temperatures with a OM617A - ErikT - 11-27-2013
I have a 1986 Mercedes G W461, ex-mil, where I've replaced the 616 with a Om617A which had run less than 200 000 km.
Last winter i had problems starting it in the cold. After quite a while without a solution, I got a tip: I poured two buckets of hot water over the left side of the engine, with the diesel pump, injectors and fuel lines. And it started easily enough. I also found I could use a heat gun to warm up that side. (the electric engine heater was inoperative at the time),
The winter ended without finding the true cause.
I noticed that one exhaust valve was very poor so I had a extra 617A head completely rebuilt by a specialist shop.
I also bought a Dieselmeken tuned M pump (and installed a new electric heater element) which was recently installed. I noticed as the temperatures dropped that the engine ran very rough when I just started it cold. The engine started easily but one had to keep the gas going for some seconds before it runs okay. While doing this there is a lot of smoke from the exhaust. It also smokes for a minute or two after I got going.
I then put on the electric engine heater and it was a lot better. The last few days I've used that when parked and now it starts and runs well. And with no more smoke in the beginning, than one expects from a 28 year on engine.
Yesterday I replaced the injectors since they where the only common parts with the configuration from last winter, to see if that help.
But no.
Left the engine heater of and tried this evening the buckets with water trick to see if this autumns problem was the same as last winter, and it started and ran much better than when cold (though not quite as well as when using the heater)
Also check some electrics:
Battery before staring: 25.6V
At rough idle: 27.7V
At higher rpm: 28V
After I had shut it down:
Battery: 25.4V
At this time the glow relay got 25.2V across the fuse and the glow plugs got 19.7V
Also the pre-glowing takes approx 35 secs but this isn't unique when compared to other cars like mine which have had the 616 replaced with a 617A.
Anyone got some ideas?
Some glowing problems despite the voltages seem okay?
RE: Startproblems on colder temperatures with a OM617A - cho - 11-27-2013
.
something is wrong with your V(olt) data.... you should get 12.5 or better
on battery... you have to test glow plugs with Ohm... bellow 1 ohm
supposed to be ok....
also 35 sec is bit long (I assume that is somewhere around 0C)
example for voltage:
Battery before staring: 12.6V
At rough idle: 13.5V
At higher rpm: no more than 14V
.
RE: Startproblems on colder temperatures with a OM617A - ErikT - 11-27-2013
No, sorry should have been more specific. It's ex military, with 24 Volt electrics.
Also the glow plugs are fairly new. When I had the problems last winter, it was with new plugs, so it they are the cause it would have to be defective from the manufacturer.
RE: Startproblems on colder temperatures with a OM617A - cho - 11-27-2013
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well that is the silly version
however Ohm test the plugs... or wires leading from relay to plugs
you have some voltage drops so you have to examine where is the source..
pile of smoke on cold start (and rough idle I suppose) in first minutes
might be just the bad/weak plugs.
sometimes only real way is to take out the plugs and red glow them
on the battery (outside of car) as some guys reported good V and Ohm data but still bad glow plug.
cheers
ChO
.
(11-27-2013, 01:58 PM)ErikT Also the glow plugs are fairly new. When I had the problems last winter, it was with new plugs, so it they are the cause it would have to be defective from the manufacturer.
that is very common these days...
which kind did you use? I had issues with new plugs so I went with NGK.
no problem since.
10w or 5w synthetic oil also helps a bit....
.
RE: Startproblems on colder temperatures with a OM617A - ErikT - 11-27-2013
Got 0.9 ohm on all, which is the same as last winter IIRC.
Think they are Bosch
5W40 synt oil
RE: Startproblems in colder temperatures with a OM617A - carlitosgy6 - 11-27-2013
you don't think those glow plugs are made to work on 12v?maybe they are getting damaged from the excess voltage
RE: Startproblems in colder temperatures with a OM617A - cho - 11-28-2013
(11-27-2013, 05:37 PM)carlitosgy6 you don't think those glow plugs are made to work on 12v?maybe they are getting damaged from the excess voltage
he probably have some kind of resistor or similar device for that...
he should look into it,...maybe the resistor is malfunctioning so the
improper V is supplied to GP....
0.9 Ohm is fine...but as said earlier in some cases one have to
remove the plugs and to red glow them to be sure....
.
.
RE: Startproblems in colder temperatures with a OM617A - Volker407 - 11-28-2013
Can you see air in the small pre-filter before the pre-supply pump?
Was the pre-supply pump overhauled?
Did you check the overflow valve if it is dirty or sticky?
Fuel filter is new I suppose?!
Gruß
Volker
RE: Startproblems in colder temperatures with a OM617A - Mark_M - 11-28-2013
I would pull the plugs and glow test them as said above. Also check they are 24v plugs, the resistance should be higher for them than 12v ones otherwise you will get too much power drawn. It certainly sounds like a glow problem as it has all the symptoms. It could also be a fuel issue if your in very cold weather. Diesel gets thicker/waxy as the temperature drops so if there is any weakness in the seals the pump will pull air through them instead of fuel. I have even had a very slightly porous fuel line through corrosion. It was bone dry but it was porous enough to let air in the system.
RE: Startproblems in colder temperatures with a OM617A - ErikT - 11-29-2013
The glowplugs are for 24V.
I pulled them and tested as mentioned. I noticed on some that it started glowing not on the tip but rather 0.5 cm or so in and from there spread to the tip.
So I bought new ones (which costs a fortune).
I started it today and while not fixed, it may be a bit better. But its also only around freezing so it may be down to higher temperatures.
I might see if I can borrow a relay so I can check if that helps.
We have different types of diesel here in Norway for different seasons. We are currently running winter diesel which is spec'ed to work down to -32 C
RE: Startproblems in colder temperatures with a OM617A - Mark_M - 11-29-2013
yes we have winter fuel here as well but it didnt solve my problem with the fuel line.
Other than mechanical issues (low compression) I am all out of ideas if the plugs are ok and you arent drawing air from somewhere.
RE: Startproblems in colder temperatures with a OM617A - cho - 11-30-2013
(11-29-2013, 08:25 AM)ErikT So I bought new ones (which costs a fortune).
you could go 12v with resistor or other V stepping down device. much cheaper option.
just a food for thoughts...
.
RE: Startproblems in colder temperatures with a OM617A - barrote - 11-30-2013
injection timing fellows, or other kind of injection problem. when cold diesel engines dont like to be advanced.
Valves usually play the smoke, anyway is posible to start well with burned valves. my 605 dont like too much the cold, usually is glow plugs. anyway one is dead with no chance of repair.
to mitigate the glow plug , u can just run diect voltage over it with a dedicated switch in a way u can control heating by yourself.
regards
RE: Startproblems in colder temperatures with a OM617A - cho - 11-30-2013
(11-30-2013, 06:50 AM)barrote injection timing fellows, or other kind of injection problem. when cold diesel engines dont like to be advanced.
makes sense,but before stretching,timing and compression,we usually start with easier things ...like GP's
(11-30-2013, 06:50 AM)barrote to mitigate the glow plug , u can just run diect voltage over it with a dedicated switch in a way u can control heating by yourself.
regards
as he has 617 yes,he has no afterglow as yours do, he can go so called "purple wire switch" to blind a relay for some time or he can simply turn
a key 2 or 3 times to override time issue.
some guys reported dead relays after this mod (it does shortens gpr life..)
simple dedicated switch with no connection to relay (direct one) has to be big and expensive as it has to pull big uuumphhhh
.
RE: Startproblems in colder temperatures with a OM617A - barrote - 12-01-2013
yep , u probably be right regarding the timing, one must keep in mind the dificulty of the task. anyway usually dificult cold start problems got to do with timing.
regarding the switch , humm is up to one wich is doing it , i personaly like to use electrically operated contactors(relays). it can be done directly , the amount of amps involved dont fry any instalation.
keep us updated , anyway mechanics got no mysteries
regards
RE: Startproblems in colder temperatures with a OM617A - swampmonkey - 12-03-2013
valve adjustment?
RE: Startproblems in colder temperatures with a OM617A - willbhere4u - 12-03-2013
When you replaced the glow plugs did you ream out the glow plug holes with as glow plug reamer? to remove the excess carbon?
RE: Startproblems in colder temperatures with a OM617A - ErikT - 12-03-2013
Swampmonkey; Yes Valves are adjusted
willbehere4u; no but as I mentioned the entire cylinder head was completely overhauled/rebuilt by a specialist shop.
Anyway, I've figured some stuff out.
First, I've must have screwed up the previous ohm readings somehow. The plugs for the 24v system, now reads approx 3.8 ohm either installed (thru the wiring) or out of the engine.
called Bosch and according to the person i spoke to, it was within spec on those plugs.
What I've learned:
A while ago, I measured how long the glow light was on when the key was turned and it was approx 35 sec.
This weekend I happened to measure it again and now it was down to 20-25 sec.
When starting it when the light goes out, the engine starts right away but runs very rough and with a lot of smoke.
But when I left it another 15 sec or so after the light goes out (after glow) it runs okay after starting with some minor smoke (expected with the Dieselmeken pump)
This was at 0 to -5 C temperatures.
So there seems to be some glow problems, but are just not sure what causes it.
Have a friend who have experienced something similar but he never found a cause for it either.
RE: Startproblems in colder temperatures with a OM617A - willbhere4u - 12-03-2013
On most of the Mercedes cars the glow plugs do run 10-15 seconds after the light turns off. On newer model cars they Evan run the plugs after start for up to a minuet for smoother starting.