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Discussion Starter #1
Wife drove to the grocery store. She came back to the R and upon turning the key, the ignition sequence just cranked the engine for about 10 sec then stopped.
No check engine light or any abnormal signs leading up to failure. I had a brand new crankshaft position sensor available to me so I brought the jack, stand and tools to the parking lot and replaced the CPS to no avail, same behavior. Next, I went to the local Advance Auto to borrow an OBDII scanner. Again, no avail, since there were either no fault codes, or this reader is not capable of reading them...
Having already performed the above troubleshooting, please tell me if my logic is correct...
Since the engine is cranking but not starting, is it safe to assume it's not getting fuel? Temp today was around 70˚F, so if there was a pre-glow failure, the engine should still start after cranking for 10+ secs. If fuel is the problem, are there any other suspects other than fuel filter or fuel pump?
Finally, is it possible that the OBDII is not cutting it and I need the STAR Diagnostics machine to read any possible codes?
Thanks for reading this far and providing your input!
-Robert
 

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Wife drove to the grocery store. She came back to the R and upon turning the key, the ignition sequence just cranked the engine for about 10 sec then stopped.
No check engine light or any abnormal signs leading up to failure. I had a brand new crankshaft position sensor available to me so I brought the jack, stand and tools to the parking lot and replaced the CPS to no avail, same behavior. Next, I went to the local Advance Auto to borrow an OBDII scanner. Again, no avail, since there were either no fault codes, or this reader is not capable of reading them...
Having already performed the above troubleshooting, please tell me if my logic is correct...
Since the engine is cranking but not starting, is it safe to assume it's not getting fuel? Temp today was around 70˚F, so if there was a pre-glow failure, the engine should still start after cranking for 10+ secs. If fuel is the problem, are there any other suspects other than fuel filter or fuel pump?
Finally, is it possible that the OBDII is not cutting it and I need the STAR Diagnostics machine to read any possible codes?
Thanks for reading this far and providing your input!
-Robert
We faced similar situations, after parking it would not start, some times after 5-10 minutes it would start.
Also in our case no error codes, it was the LPFP (feeder pump) that had failed, it took the dealer ship long time to find and they had to do some out of the box search to find it.
Funny enough the LPFP must be the only part on this MB that is not supervised and will throw an error code...:surrender:

Hope above will help you
 

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Discussion Starter #3
Funny enough the LPFP must be the only part on this MB that is not supervised and will throw an error code...:surrender:

Hope above will help you
Thanks 2008R320,
Do you mean it must be the only part that doesn't throw an error when it fails?
After some reading on the W164 forum, it seems that others who had similar issues had their LPFP replaced as well... The only difference is that mine won't start even after sitting for several hours...
-Robert
 

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Thanks 2008R320,
Do you mean it must be the only part that doesn't throw an error when it fails?
It look like it, even small light bulbs will give you a warning, I'm just surprised that the LPFP does not have a minimum pressure that it has to deliver, if below it would set CEL or at least store a code, it is a quite essential part on the engine.

Hope that you get it repaired and back on the road.
 

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Discussion Starter #5
After some searching on the other forums regarding the CDI engine, it seems that the LPFP or "delivery unit" fails pretty often.
From what I can tell, the fuel filter filters fuel going into the HPFP or the IP, but there doesn't seem to be a filter that filters fuel going into the LPFP?
Can someone confirm? Eric, do you have any experience with this?
If this is correct, then is it safe to assume that I can test the LPFP by disconnecting the feed line to the fuel filter that sits on top of the engine while cranking to see if fuel comes out? If it doesn't then surely it is the LPFP that has failed?
Thanks,
-Robert
 

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Discussion Starter #7
Kent,
I don't think your post contributed anything and did not answer any of the questions I clearly stated in my post. I know an OBDII scanner may not list all of the stored codes be it a MB gasoline or diesel engine. In this case it seems that the STAR diagnostic computer did not reveal any additional fault codes either.
Please get off your high-horse and refrain from posting if you do not have anything useful to add.
Thanks,
-Robert
 

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Discussion Starter #8 (Edited)
update:
I replaced the "low pressure fuel pump" (Lifter pump) and the R is back on the road again.
Of particular noteworthiness is the fact that in all cases I have read or heard about, the onboard monitoring system does not register a fault code. It did not throw a CE light and did not store any codes. Both a standard OBDII scanner as well as the MB Star Diagnostic system revealed no codes.
I will start a new thread to document the lifter pump R&R.
-Robert
 

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If the lifter pump is the same set up as TDI Jetta's then one can normally here it buzz to prime the fuel filter when the ignition is turned, usually under the rear seat in a jetta/golf tdi. The R&R will be useful for members.

Turning the ignition should also spurt diesel to the filter, question is which pipe
 

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Discussion Starter #10
There is a sound, but the sound is more of a low frequency hum than a buzz. It's hard to hear with the cover, carpet, and rear seat in place if you don't know what you're listening for. Add the pump for the rear suspension that turns on upon start, it becomes harder to pick out.
 
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