W203 cdi EPC Fault

renrutp76

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some of my recent threads highlight the issues I have been having. Here is a brief summary:-

Car was initially hesitating under acceleration at low RPM, initially thought to be a gearbox issue, however my opinion was air in fuel after checking a clear section of pipe. A temporary clear section was between the bulkhead and the fiilter, air was coming from the tank.

All plastic and rubber fuel lines have been replaced.
Leak off pipes have been replaced.
Fuel filter has been replaced.
HP pump has been refurbished (new seal kit).
EGR valve cleaned.
Fuel tank is full.

After all of the above, car was very difficult to start, ended up suspending a container of fuel directly onto the filter.

Just didn't feel right, more engine vibration than normal, also lots of hesitation when revving. Took car to local garage, no star, but did have a Snap-On diagnostic, all values were within spec (although MAF reading was slightly erratic), no faults logged. Drove the car 3 miles home and on a long straight floored it, car shut down with an EPC fault.

The injectors were tested a month ago by a MB indy on a star machine and all were within spec, this was also after an EPC fault.

Any more ideas? :confused: :(
 

turbopete

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contaminated fuel? id guess live data needs to be viewed when the incident occurs to ascertain the fault
 
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renrutp76

renrutp76

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Thanks Pete,

I still think its air ingress, don't know where from after £145 of plastic pipes and fittings :shock:. I will see if I can find a garage with star early next week.
 

turbopete

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when i got my car, despite it being in the family (dads car before mine) and knowing for SURE we had never misfuellede (according to the pump used) my car did this for a while. next time i put fuel in, i could smell PETROL from the filler neck. i put a LOT of diesel in to dilute it, and it hasnt put the epc light on / cut out since
 

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Ref the epc fault.........check all the electric plugs on top of each injector are making proper contact (check the terminals are clean and not burnt)
 

Dannyboy201062

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Hi RenratP76, may be some help.....I`m new to the CDI mercs and on a learning curve....but my during my recent problems/ posts......C270 CDI .."fuel filter disaster" and
"C270 CDI won`t start"......both were fuel starvation / bleeding issues......got them sorted but I got this fault " EPC " displayed during both problems and it went away when the car was running properly again.
Dannyboy 201062
 

Dannyboy201062

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Hi Renratp76........correction to my prev post......it was an EPS fault that showed during both events......battery would have been disconnected during both issues. So not an EPC issue.
dannyboy
 
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renrutp76

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when i got my car, despite it being in the family (dads car before mine) and knowing for SURE we had never misfuellede (according to the pump used) my car did this for a while. next time i put fuel in, i could smell PETROL from the filler neck. i put a LOT of diesel in to dilute it, and it hasnt put the epc light on / cut out since

Hi Pete,

My car has been doing this on and off for about 12 months (7-8 occasions). On each occasion the engine has been under full load hard acceleration or kickdown. defineately no smell of petrol in the tank. I has been a a star machine twice, no faults were logged, indy couldn't replicate. Last time I picked the car up, got 2 miles down the road (after being told nothing wrong) floored it, and sure enough dreaded loss of power and warning light on the dash. Turned round, went back to the garage only to find that they had locked up and gone home :mad:. Every time it has faulted in this way, it has started again immediately after.
 
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renrutp76

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My car has been doing this on and off for about 12 months (7-8 occasions). On each occasion the engine has been under full load hard acceleration or kickdown. defineately no smell of petrol in the tank. I has been a a star machine twice, no faults were logged, indy couldn't replicate. Last time I picked the car up, got 2 miles down the road (after being told nothing wrong) floored it, and sure enough dreaded loss of power and warning light on the dash. Turned round, went back to the garage only to find that they had locked up and gone home . Every time it has faulted in this way, it has started again immediately after.
 
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renrutp76

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Update:-

Just taken car to MB Tech in Warrington for diagnosis, first time there, everyone very helpful. Ran a leak off test, all 5 injectors out of spec :shock:. The tech recommended replacing the HP Pump first, as often replacing the injectors will not solve the EPC shutdown fault.

Big thanks to everyone at MB Tech for seeing me at short notice.
 

Stability

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Why don't you get the injectors reconditioned ?

You can see the HP pump actual value on a star to eliminate it.

Sounds like you've sorted it !
 
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renrutp76

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Rail pressure was checked on a snap on diagnostic, steady @ 300 bar. Although all injectors failed leak off test, the tech said that replacing all the injectors may not necessarily rectify the fault, and to go for the pump first. Should I ignore him and do the injectors?
 

Stability

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Id trust him - its his reputation which I'm sure he cares about !
 
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Ran a home made leak off test, 3 faulty injectors. Replaced using remanufatured units from KMS in Birmingham (ebay) £130 each with a £35 rebate once old units are returned. Car running great, except stil cutting out under full load :? Pump next!
 
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renrutp76

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Finally got round to replacing the pump, after starting got more and more difficult. Now pulls like a train again, and no EPC fault :D.

Struggles to fire when warm/hot :Oops: Time for another leak off test!
 

turbopete

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it could be the start of the crank sensor (CPS) failing also
 
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renrutp76

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car seems to be starting ok, but upon finding a long straight, I floored it from 40 mph in 5th gear, 1st kickdown was ok, but second kickdown brought up the dreaded EPC fault. I ran a leak off test once again for 2 mins:-

Cylinder 1 35ml
Cylinder 2 35.5ml
Cylinder 3 35ml
Cylinder 4 36ml
Cylinder 5 27ml

Should I be concerned about cylinder 5?
 

Steve@Avantgarde

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I would say if it has rail pressure, 300bar was mentioned, how can the pump be at fault?? If the pump fails, the engine wont start and the rail pressure wont lift above 2 bar which is the lift pump pressure! Basic engine diagnostics.

Your EPC fault will be failing injector(s) caused by worn injector nozzles, nothing to do with leak off necessarily. The fuel will dump through the injector and not spray a nice mist into the cylinder. The only way to test is to remove the injector and send to a diesel specialist to bench test.

The purpose of leak off test should be done if you are having trouble starting the engine and should be done with the camshaft sensor disconnected for 30 secs or so. If you have a high spill then that injector requires replacing. You could also try a hard throttle leak off test to see if one is breaking down under load. The other thing to check is the mg/hub limit quantity correction. But you will need STAR for that.
 
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renrutp76

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Hi Steve,

The initial problem was cutting out with an EPC fault, which I was advised was caused by rail pressure deviation by a non MB tech who checked live data with a "snap on" diagnostic and confirmed that the rail pressure was stable at 300 Bar. However, the fault only ever occurred under heavy load conditions. The next tech who looked at it recommended testing the injectors, they have star, but whether this test was carried out at idle or under load I am not sure. He told me all 5 injectors were out of spec, but even replacing them all may not cure the fault and his gut feeling was that the HP pump was worn. but I wasn't convinced as the car seemed to run reasonably well. I carried out my own leak off test at idle, and found three ( 2, 4, & 5) were a lot higher than the other two. I replaced the three, drove it for a day or two before flooring it, and it cut straight out. I then replaced the pump, and the car ran noticeably better, but developed a warm start issue, which has miraculously cured itself. My car runs noticeably better, but still has a fault which people seem unable to diagnose. I have paid for an injector that has a noticeably lower leak off rate than the others, do I need to return it and get a new one?
 

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Yeah have seen the exact same issue on a om612 with 220km on it. Car starts, runs and drives just fine. But as soon as you floor it and put it under instant full load, it cuts out with epc light.

It turned out to be the HP pump. The ecu is suddenly asking for a certain rail pressure, but the pump can't deliver it in time due to wear or crud or whatever. Fitted a used pump from a lower km vehicle and the problem is gone. The original pump had a buildup of small hard black deposits inside it.

And you want lower leakoff, its when its too much that they need replacing. Don't get confused with the injection corrections for smooth running. That is the test that will show if an injector is injecting properly relative to the others. Leak off test just helps with starting issues.
 
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