ML270 Cdi slow starting.

[BIGjoe]

For several weeks I've been aware of the car taking slightly longer than normal to fire up from cold. Well this morning it was not having it, after several attemps it refused to fire at all. A quick look at the exhaust and no vapour, so lack of fuel hence no ignition. A burst of easy start got it to fire and away she went. The tank was nearly empty, so I'm thinking fuel pump/lift pump not pressurising the injection system, is this giong to be expensive .

 

[panason1c]

More likely to be one or more injectors faulty.

 

[Dieselman]

Or an air leak into the fuel pipe near the filter.

Start by looking for air then perform an injector leak-off test.

See:
http://www.mbclub.co.uk/forums/showthread.php?t=55040&highlight=injector

 

[BIGjoe]

Or an air leak into the fuel pipe near the filter.

Thanks DM, thats what I'm thinking it may be, when the tank is full, it starts instantly, but below half full starting takes longer as all the fuel in the system has run back into the tank drawing in air as it goes.

 

[BIGjoe]

Had an investigation today, can't see a lot wrong, but going to try replacing the pipe between the filter and pump. Whilst the plastic top was off, was amazed to see a mass of black gunk around an injector, one of the infamous copper seal failures no doubt , and another job to boot.
I've heard horror stories about getting the injectors out, is it best engine cold or hot, and any other tips.
TIA.

 

[BIGjoe]

Right, finally got round to having a play under the bonnet. No 3 injector has a serious flow of fuel through the return port, so is goosed and no doubt the cause of the starting problem, and every other injector is leaking combustion past the seal in different velocities, except No3 of course.
Looks like I know what I'm going to be doing over christmas.
Any tips for removing gunked up injectors, is it easier when the engine is hot?, and is it worth using a liquid gasket with the new sealing washer. I've used blue goo on other machinery in the past with succes

 

[BIGjoe]

Ok, job sorted. after a good long run, the carbon was nice a soft , so it came away in great big lumps. The injectors came out without to much of a struggle, found the best way was to loosen the retaining bolt first, and with electric plug and fuel pipe still connected, start engine which dislodged the injector, then remove bolt/electrics/ fuel pipe, and then slowly twist back and too with mole grips until injector could be pulled clear. A thorough clean and a good blast of compressed air, then replaced injectors with new washers/liquid gasket and bolts, with a new injector for no3 cylinder (£143, Merc Warrington).
Result:now runs as sweet as a nut, with instant starting (-5' here yesterday morning)

 

[jaymanek]

You are lucky they came out so easy... they are not always so... we have invested in a Klann removal kit as normally they are stuck solid..

 

[BIGjoe]

You are lucky they came out so easy... they are not always so....

Wasn't I , after reading so many horror stories about the blessed things refusing to leave their nests I was dreading the job

 

[proser]

I found Mr Muscle oven cleaner was very good at cleaning everything up and dissolving the carbon build up.