X164 OM642 engine cuts out

[tony jr]

I am having problems with my GL320. The engine will turn over easy and start. It will run fine for about 30 seconds then cut out. Any ideas what the problem could be? I have a Creader VIII and the only code I picked up was P0340 camshaft position sensor. I cleared the code started the engine and it stopped the same but no fault codes logged suggesting that that was an old code. The only other background is that I have just changed the air suspension pump due to the old one failing and blowing the fuse


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[umblecumbuz]

Do you park facing uphill?

 

[tony jr]

Do you park facing uphill?

On the flat but with the suspension failing the front has been down and the back up for the past week


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[tony jr]

Just a thought: could the replacement compressor relay that I was given at a high street parts shop have been the wrong one! I have switched it back to the old one but still same problem! If it was wrong could it have damaged any component or circuit? If it has I’m really annoyed because I specifically asked the guy if it was compatible


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[mioba]

Just a thought. it could be something as simple as a vaccum leak. Get to a good indy. I use mercserve on Radford Road, Roger and Nate there are top top blokes.

 

[malcolm E53 AMG]

Does sound like a crankshaft position sensor failing to ground as the engine begins to warm. Certainly the first thing I would replace especially in view of the fact that you have that fault code. What makes you think that the sensor isn’t the problem as the engine is showing typical CPS symptoms?

Regarding the air pump I would change the relay which should be done at the same time as the pump

 

[tony jr]

Does sound like a crankshaft position sensor failing to ground as the engine begins to warm. Certainly the first thing I would replace especially in view of the fact that you have that fault code. What makes you think that the sensor isn’t the problem as the engine is showing typical CPS symptoms?

Regarding the air pump I would change the relay which should be done at the same time as the pump

The only reason why I didn’t think it was the cps is that when I cleared the fault from the memory and started the car with the same problem it did not show any code when I read the codes


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[tony jr]

Hi Malcolm,
Did you mean camshaft position sensor or crankshaft position sensor? I ask because the code I had was for the camshaft sensor A bank 1

Regards

Tony

 

[mersum1es]

camshaft sensor won't shut down engine (it is used only sync the crank sensor), but universal code readers often fail to isolate which one sensor is faulty. If cut out is because of real fault, a code should be strored. If even SDS won't find a fault code, car thinks event was righteous. I would go direction of fuel delivery (fuel quantity valve), or boost problems (EGR) especially if car puffs some smoke.

 

[tony jr]

Could it be a problem with the back-pressure sensor?


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[malcolm E53 AMG]

Hi Malcolm,
Did you mean camshaft position sensor or crankshaft position sensor? I ask because the code I had was for the camshaft sensor A bank 1

Regards

Tony

https://www.ebay.co.uk/itm/Genuine-...aft-Position-Sensor-A6429050000-/111403151133

 

[tony jr]

Hi all,

Just to fill you in on where I am with this. I had already ordered a camshaft position sensor before I got Malcolm’s message so decided to fit it anyway. After fitting the car started ran for about 30 seconds before stopping again as before. I read the codes and got P0341 camshaft position sensor A circuit bank 1 or single sensor despite changing the sensor. Not sure what to try now. Should I try replacing the crankshaft position sensor or look at the wiring?


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[malcolm E53 AMG]

CPS is relatively cheap so certainly worth doing due to the fault symptoms

 

[tony jr]

I have read a thread stating that a excessive exhaust back pressure signal from a faulty sensor would cause OM642 engine to start run for a short while then cut out. When the unplugged the sensor the car would run as normal. I have just tried this to no effect.


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[tony jr]

Hi Malcolm,

Many thanks for your advice - sounds like a good plan. Is it easy to get to I can’t tell in the dark.

Regards

Tony


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[umblecumbuz]

Once the car starts, the cam position sensor is more or less redundant. The ecu will take it as read that the cams are in sync with the crankshaft thereafter, otherwise the engine would not continue running.

 

[malcolm E53 AMG]

https://forums.mercedesclub.org.uk/index.php?media/om642-crank-sensor-location.2793/

 

[tony jr]

I am told that this might be a problem with the fuel pressure either an injector or the high pressure pump. What values should I be seeing with this engine? Would a drop in pressure cause the engine to stop?


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[mersum1es]

Would a drop in pressure cause the engine to stop?

Yes. But low (or high) fuel pressure always triggers a fault code.

by SDS you can do tests for the pump, rail pressure regulator and fuel quantity valve.

 

[tony jr]

What I can read with my scan tool is:
With the ignition off a rail pressure of 870 KPa
When it starts the rail pressure is 30,000 KPa
When the engine cuts out the pressure drops over a minute back down to 870 KPa

I don’t know what values to expect and if these are as expected.


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