ml270 cdi difficult start,engine cut with EPC light on acceleration

[tsu]

hello.my ml270 has long cranking no matter the conditions. if its cold,hot ,hasnt started in a week hasnt started in a minute always the same.On heavy acceleration the engine shuts off with epc light. Previously this was solved by changing fuel filter .Now i have changed fuel filter,fuel line from lpfp to hpfp , injectors have normal return and the diesel tech told me that he has seen injectors with 5 times the return amount as mine and still didnt cause problems.Rail pressure is within normal range and rises as soon as cranking begins ,pressure regulator is ok, there are zero bubbles in all fuel lines .Last thing ill try tomorrow is find a used low pressure lift pump to test if theres any change although the technician told me this fails once in a million. The car is running on red diesel for the majority of its life idk if this could cause any problems MY 2001 350000km Any ideas appreciated.

 

[oigle]

One in a million???? Yeah right!! There is an O ring seal in the lift pump that flattens with age and fails to seal properly. This allows air to ingress which then stops pump working. Took my mech a while to find it. New seal and all OK again. Cheap fix but hard to find.

 

[tsu]

An update : I hooked it to star diagnostic ,in idle test it shows number 4 injector return is 0.8 which mechanic said is too high and is probably the cause of the issues also injected quantity was 5 when it should have been 8 I don't know if we're talking about mL or mm^3 but those where the values I remember. Rail pressure is 262 bar which mechanic said is normal . The interesting thing is the real life test (hooking tubes to the returns of the injectors shows all of them to be perfectly normal ). I am starting to believe there is a chance that the number 4 cylinder has some other problem and maybe star thinks injector is returning but all the performance is there (until it cuts out with epc) and idle is smoother than a V12 .

 

[tsu]

Oigle here's the amount of bubbles coming from lift pump definitely o ring on its way out but 3 bubbles I don't think it's enough to cause this kind of long cranking

 

[oigle]

Oigle here's the amount of bubbles coming from lift pump definitely o ring on its way out but 3 bubbles I don't think it's enough to cause this kind of long cranking

My experience indicated that when enough air leaked in, the geared fuel pump was unable to pickup the fuel as there was air in the gears. Would just crank for a long time and often not start at all. Of course, you seem to maybe have other issues too. It is an easy fix if you can acquire an o ring to suit. Not available in Oz and had to make one!!

 

[tsu]

just wanting to answer this for anyone looking for the same problem. The problem was fuel presure regulator in the back of the rail . The diesel technician supposedly specializing in cdi systems assured me that he tested it and it worked fine . a refurbished one off ebay did the job although you might be able to get away with even less as the valve itself is usually fine and the problem is in the o-ring of the regulator being flat and allowing pressure to bleed back into fuel tank.Once again proves that no dealer or technician knows what hes talking about and if you have the time you should get the job done yourself. The mf scammer even insisted i should buy his refurbished cp1 pump as he said mine was destroyed. Dont fall for such scams people these pumps are indestructible you have to run sand through them to do any damage.Maybe if you have a milion kms change the seals and gaskets but not the entire pump.

 

[FlorinM]

@tsu thank you sharing what was the actual problem in the end.