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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3721
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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Unhappy Great E350 if only I could figure out CEL Rail

Customer Question

Unhappy Great E350 if only I could figure out CEL Rail pressure troubles
Hi hoping you could give me some help on this I have a usually great 2009 E350 W212 CGI. It has done 50k Kms
Been crazy for past 3 months. Typical day Car starts ok in mornings. Drive a short distance say 30 miles. Park car to do errands and start again in a few minutes. Almost immediately while speeding up CEL light goes on and there is a slight jerk. There is a loss of power on acceleration but car moves on with notable poor performance but not in limp mode. Check with my mechanic and error message is rail pressure high. Once in a while it would say low. This is always the same error messages. After resetting system car goes on fine with the check engine light sometimes coming on but usually clears by next day
However, I've noticed that if I stop the car shortly after the CEL comes on then I have a nightmare because thereafter the cars performance is poor and continues jerking and no power when I press the accelerator particularly when I kick down. Even worse is the mornings when the start is very cold with the car shuddering for a few minutes before eventually settling but having poor performance. All this disappears once I reset at the mechs
I've also noticed that if I park for longer say over an hour then the CEL does not pop up and there are no issues. This leads me to believe that there must be some relation to engine temp and the cooling of engine
We've changed the rail pressure sensor with no luck which my mech was convinced was the issue. Now my mech says it could be a faulty ECU so we should replace. I get the feeling He's not sure to be honest and I'm trying to avoid the journey of throwing money in and hoping that we eventually find the problem 20 parts later
It's such a great car with fantastic power and it's really frustrating that we can't figure this out. I'm now at my mechanics once a week at least to reset error message when it does not clear itself out. Can You help PLEASE
Submitted: 9 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 9 months ago.

Hello. Rail pressure issues can be a real pain to diagnose. What is the exact fault codes you are getting ?

Customer: replied 9 months ago.
Thanks for your response Lou. Cant remember the exact code but as 'luck' would have it issue happened again today. Fault did not reset itself after appearing yesterday just before getting home. Very cold start this morning and had too restart ignition about 5 times before it picked and eventually settled a bit. Car has been jerking whenever i accelerate a bit harder throughout the day. So of too my mechanic tomorrow morning for a reset and will get you the code... i'm pretty sure that it says rail pressure high but will re-confirm the exact number..Used to give erratic readings even when my mech checks it and the car is idling which is why he was confident it was the sensor..... Any clues on what i can ask my mech to check on tomorrow morning?? you help me figure this one out and i'll owe you big time
Expert:  Lou P. master tech replied 9 months ago.

Ok so I will need the exact code number or a picture of it cause the same code can have three sub codes indicating further issues and can help with diagnosis. Also he needs to verify low fuel pressure pump pressure up to the high fuel pressure pump. He may not have a high pressure pump fuel gauge as they are expensive but he should have a low pressure one. There is a quantity control valve in the high pressure pump that limits fuel to the rail. So those could be the culprits. Low pressure fuel pump in tank. High pressure fuel pump on front of engine or quantity control valve on high pressure pump. At least for now until we get the codes. Hope this information helps. Have a good weekend :)

Customer: replied 9 months ago.
Cheers ***** ***** get back to you after i see him tomorrow
Expert:  Lou P. master tech replied 9 months ago.

Sounds good :)

Customer: replied 9 months ago.
Hi Lou,Spent quite a bit of time with my Mechanic. The error code is 1141. I have attached the screen shotHe noted that immediately after the fault occurs the readings for Rail pressure is at 5 bar as per attached which seems to be a direct contradiction to the error code. The rail pressure seems to correct itself to around 200 bar a while thereafter but car still jerks when in motionFor this reason he strongly now believes its the high pressure fuel pump. He asked me also to attach and share with you the the page on low pressure limp mode for your thoughts
Expert:  Lou P. master tech replied 9 months ago.

ok something does not make sense, is your car gas or diesel?

Expert:  Lou P. master tech replied 9 months ago.

i ask this because your story made me believe it was a diesel engine, yet the computer module your mechanic is looking in for the fault code is a v6 gas engine i realize you are in kenya from what the site tells me but the engine your tech is looking at with the scanner is not a engine that has a high pressure fuel pump or even a rail pressure sensor, the m272 engine is a gas v6 engine. now the m276 has a high pressure fuel pump? we need to straighten this out before we confuse each other further, i want to be 100% on the same page, can you give me your vin number?

Customer: replied 9 months ago.
Hi Lou, Its gas (CGI)
Customer: replied 9 months ago.
Hi Lou, Its gas (CGI) The V6
Expert:  Lou P. master tech replied 9 months ago.

OK, what is your vin?

Customer: replied 9 months ago.
VIN WDD(###) ###-####062012
Expert:  Lou P. master tech replied 9 months ago.

OK, wow, lol i did not know they made that engine with direct injection. ok so i dont think the high pressure fuel pump is the cause if the low pressure because if you look in your picture where it shows the value, the SPECIFIED value is the same, which means the engine control module is telling the quantity control valve to lessen the pressure, we need to see the specified and actual fuel pressure before the fault occurs.

Expert:  Lou P. master tech replied 9 months ago.

so when the code occurs, your tech can double click on the fault code to access the test procedure . have him follow that, i will check to see if i can also access it on my end.

Expert:  Lou P. master tech replied 9 months ago.

we will have to work through his scanner as my system is for usa and mercedes does not show other countries other than canada. BUT i will try one other outlet

Customer: replied 9 months ago.
Hi. Mech says that the actual values are as per the values on the screen photo titled reading once stabilizedHe feel that the high pressure pump is failing leaving the low pressure pump to run the system on the 'limp mode' thus the 5 bar reading ??
Expert:  Lou P. master tech replied 9 months ago.

OK see the specified as 200 but the actual is 208, that can be the reason, when the fault occurs the code will store whats called "freeze frame" so it may show the pressure in the code when you click on the fault code to expand the info. if that makes sense. 5 bar is about 75 psi and the fuel pump may only put out about 60 max so i would suggest the quantity control valve. if anything at this point.

Expert:  Lou P. master tech replied 9 months ago.

also check the pressure as you run the engine at higher rpms and in gear and while driving to see what they do.

Expert:  Lou P. master tech replied 8 months ago.

any luck?

Customer: replied 8 months ago.
Hi Lou.... Been busy week for me. My mech is trying to figure out how to test the high pressure control valve. Could be the issue ... then from there we move to the high pressure pump i think
Expert:  Lou P. master tech replied 8 months ago.

ok gotcha.