Help needed c250 diesel hunting when cold

[Fancypants]

I have a 1994 class 2.5 diesel non turbo mercedes which has never given me a problem until one of the injector pipes on the injector pump began leaking. I had all five injector pipe outlets resealed and the other part which 2 fuel lines come out from replaced. From when this work was carried out it has started ok but when the engine is cold it violently shakes. I understand this is termed hunting. Once the engine is warm it stops and runs perfectly. I have also replaced all the fuel lines and there is no sign of it drawing air anywhere. Does anyone have an idea what else I should look for? Any ideas would be appreciated.

 

[mebobster]

hi, please find the time to take a look at my thread, i think i have a similar problem, never come across the term Hunting, im assuming it refers to the fact that the engine is hunting for 100% fuel on start up, ive done quite a lot of work to mine to no avail! and it seems the forum is either sick of me or have run out of ideas! please do let me know if you find a solution, i would be grateful...

 

[Bolide]

I think that'll be a turbocharged 605 engine. The fault is common to the 605 and the 606 versions of that engine

The idle is stabilised by electronically controlling the position of the fuel rack in the injection pump. So the first diagnostic would be to pull the electrical feed off the rack and see if it still hunts

Hunting implies a feedback loop as per idle stabilisation. As the revs drop the ECu senses the drop & adjusts the rack position to feed more fuel. As the revs rise to the idle rpm the ECU backs off to stop it overshooting. If this change is not properly damped it'll overshoot the idle rpm, drop too low and then the cycle starts again. That's one type of hunting

Typically on a 605/606 when the fuel system is disturbed, perhaps when the fuel filter is replaced, you get air leaks due to flattened O-rings. I suspect your problem is due to something else being disturbed. If there's a damper on the fuel rack I'd start looking there

As the problem started after you had work done I'd also question whether the washers & delivery valves were refitted properly

See:
http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=M&cat=19T&SID=07&SGR=045&SGN=01

Nick Froome
www.w124.co.uk