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OM642 CP3 upgrade
WSchotty Offline
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#1
OM642 CP3 upgrade
My CP3 pump has started rattling on my early OM642, so I decided to try and upgrade to the later pump from the OM642LS engine.

Here you can see the pumps side by side:

   

The differences for the connectors are the control solenoid being reversed, and the high pressure connection is around 3mm forward on the updated unit.

The part numbers are as follows:

1600 bar, original for early OM642: A 642 070 03 01

1800 bar, found on OM642LS: A 642 070 12 01

The later pump installed on the early engine with only loosening of the wiring harness and shifting it forward a couple cm. The high pressure fuel line had to be removed and reshaped to fit the new location. Everything else was just like installing the old pump.

Here is the new pump installed:

   

Now everything is running, but of course I am getting a high rail pressure alarm with mid to full accelerator application since the relationship between the rail pressure, accelerator, and load are different for the higher output pump. I have contacted GDE to see if they can calibrate for this.
04-17-2017, 05:22 PM
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WSchotty Offline
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#2
Sad  RE: OM642 CP3 upgrade
After monitoring pressures while driving with the new pump, I have come to the conclusion that this is not something you want to do unless you swap the remainder of the fuel system from the later om642 engine also. Peak observed rail pressures are around 26000psi, which will accelerate wear on the injectors and cause the rail relief system to fail. I'm going to just swap in a new pump of the original style, and shelve this idea until I have an actual om642LS engine to play with. In theory you could change the rails with the higher pressure system and run the old injectors, but there does not seem to be that much of a performance improvement for the cost of all the upgrades which are required.
04-23-2017, 01:29 PM
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starynovy Offline
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#3
RE: OM642 CP3 upgrade
What? Big Grin Save the hassle with changing pumps around. Your conclusion is bullshit as any deviation of rail pressure will shut down engine immediately. So forget about some large pressure spikes, if it goes to 26 000PSI then it is ment to be. Normally pressure spikes cca. 20Bar around setpoint if it would be greater spike it will shut down again. You are not gonna wear injectors nor DRV valve.
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04-23-2017, 02:51 PM
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Turbo Offline
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#4
RE: OM642 CP3 upgrade
Do do you know the injector angel for the injectors? on the old om613/om648 it was 156 degrees
I do wonder if it is possible to swap in the new steel pistons in the om642 engine? I have not seen if they charge the diameter of the pistons.
anyway I will son have a om642 engine to work on
04-23-2017, 03:03 PM
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WSchotty Offline
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#5
RE: OM642 CP3 upgrade
(04-23-2017, 02:51 PM)starynovy Wrote: What? Big Grin Save the hassle with changing pumps around. Your conclusion is bullshit as any deviation of rail pressure will shut down engine immediately. So forget about some large pressure spikes, if it goes to 26 000PSI then it is ment to be. Normally pressure spikes cca. 20Bar around setpoint if it would be greater spike it will shut down again. You are not gonna wear injectors nor DRV valve.

No bullshit here. It seems EDC 16 adapts to the new curve itself, but does have a high limit in the software of 25000 psi. I am guessing the 23000 psi (1600 bar) system has a 26000 limit on the physical safety release. I am assuming this based on the similar Bosch system used on the Cummins trucks of this vintage. See here about their tales with the valve, known to fail after repeated actuation: https://www.dieseltruckresource.com/foru...ck-257963/

If the software limit is removed the valve will dump the excess pressure back into the return line. Check it out driving around with a gauge when I bounce it off of 25000 psi:

https://youtu.be/ZPcyOee1JiE

A bit better quality, still bumpy because on 30mph road:

https://youtu.be/Yr8co42057k

With the rails (and relief valve) off the 26000 psi (1800 bar) system this could be avoided, but I'm not sure the expense is worth it until I have the rest of the better engine anyway as this one is already getting hot with the tiny turbo/ intercooler and existing fuel system.

part numbers for the newer style fuel rails for future reference:

642-070-30-95 Right

642-070-34-95 Left


Quote:Turbo


Do do you know the injector angel for the injectors? on the old om613/om648 it was 156 degrees
I do wonder if it is possible to swap in the new steel pistons in the om642 engine? I have not seen if they charge the diameter of the pistons.
anyway I will son have a om642 engine to work on

No idea on the injectors, I haven't had to deal with any issues on this engine in that regard. I know the new ones are 8 hole... that is about it. The new engine has a different piston with additional space in the cup for less compression, and different heads with extra cooling capacity, so that is the one to tune if you can find one on the cheap. There is also a different coating on the cylinder walls and piston skirts, but the diameter may be similar. The individual used parts for the LS are still cheaper than the early ones as they aren't breaking as much yet. I picked up a used turbo and pump off the LS for under € 500 from Lithuania on ebay - probably stolen though. You can get the used 8 hole injectors for less than 80 € each on there too, new 350 +...

Here is the part number for the later injectors for anybody interested: 642-070-11-87

I'll leave the fuel system stock on this engine, and put the bigger bb turbo on it and call it good. When the engine grenades in 500000 mi I'll start trying to tune the LS block to the EDC 16. This thing is just towing around trailers occasionally, and will be the DD when I start stripping down the W126 for the body resto and 606 swap. Do NOT want to melt the engine quite yet, cheapest used LS around here is still $10k and up, just figured I would see what happened since I had the LS pump already anyway.

Anybody want to buy a LS pump? Will sell for the low price of 500 € Big Grin
(This post was last modified: 04-24-2017, 02:42 AM by WSchotty.)
04-24-2017, 02:37 AM
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