om651 w204 fuel problems

[paul crx]

afternoon all,

I am new to the forum and looking for some opinions on a strange problem I'm having with my 2010 c class blue efficiency with 651 engine, hoping someone with more merc experience than me can help.

my car started to run out of fuel at just under 1/4 of a tank, the first time was just after an oil change but I think that was purely coincidental. there were no codes thrown this time, it just cut out. jerry can of diesel and after priming a few times it started right up again. the second time was a month or so later (the tank had been run down to red a couple of times in between). at this point i got the code 0087 fuel rail pressure too low. i changed the fuel filter using a mann item (which is OEM I believe?) as I knew it probably needed doing anyway and i was hoping for an easy fix. however it has since cut out twice on 1/4 tank now and to be honest, I believe it will do it every time unless I fill up before.

i checked data on my obd2 scanner and I see 58psi at the rail when priming which is good, but if I leave it that suddenly drops to 14.5 psi then back to 58psi (one or the other, nothing in between) then settles on 14.5psi. is this normal? car starts absolutely fine and running fuel pressure is within the acceptable range but it does fluctuate a fair bit.

i have leak back checked the injectors which were all spot on, and also replaced the leak off tubes.

i have decent return flow to the fuel tank.

what are your thoughts on the fuel pressure and running out of fuel early? i know lack of return pressure can cause havoc with the venturi effect in the tank but it seems pretty decent... i have no idea how much should be coming back and at what specific rate though.

any thoughts and opinions would be greatly appreciated.

thanks,

Paul

 

[Doug1234]

Saddle tank syndrome ?? One side of tank has no fuel in it , fuel tanks cannot balance .. keep it over half full is the cheap option

 

[paul crx]

It’s something I’ve considered But it’s 1/4 tank where it cuts out, not half. I also opened up the tank and there was relatively even amounts of fuel in either side… bizarre.

 

[Doug1234]

1/4 tank is where they normally play up and run out

 

[paul crx]

Hmmmm. On a slightly positive note, i was feeling brave today and actually got it under quarter of a tank for the first time after doing the leak off pipes… going to try and run it down a bit lower tomorrow, here’s for hoping!

 

[paul crx]

Update. Today I saw the fuel light come on for the first time in 2 months! Happy days.

I’m going to run it down twice more before I can happily say I’ve cured it but it’s looking good.

This could have been either fitting new injector leak back nozzles, and taking out the metal tube connector at the end of them.

I did also look at the fuel filter again and I could see a tiny amount of diesel had accumulated around the top of it where the sensor is. Mine is the one with the 3 pin removable sensor as opposed to the newer 5 pin ones with water drain pipes so I simply popped a thin m5 washer under the metal bracket on the filter in order to push the sensor down just that little bit further allowing the o ring to seat a little bit better which seemed to stop the ‘leak’.

That still leaves the original fuel pressure question though, anyone have any thoughts?

 

[Dean Fletcher]

Might be a stab in the dark but when I had my e250 om651 the rail sensor was a bit dodgy and come off the rail slightly caught me out at an airport once all it took as a push back in and fine again. Fuel rail pressure on a om651 diesel is quite high

 

[paul crx]

How does that work? The sensor is threaded in and the plug itself isn’t under pressure. Unless you mean the one at the back of the rail? I haven’t really looked at that one.

 

[paul crx]

Update! It ran all the way down to the light again today and as I was feeling brave I ran it to the refill now message. I am pretty confident the issue is now resolved!