Response to Marshall's questions,

(Apologies if this isn't the way to reply, but I couldn't see any other way using the mail digests)

I've asked the question before about the difference in the 190 2.5l diesel and the engine in my C Class. The answer that came back was it was much the same except mine has 4 valves per cylinder. I asked this question as I can get a 3rd party service manual for the 190 series here in Britain, but not for the C Class (yet).

I can't say if there's a link between the problem and the level in my tank, but I'll now take note. My drive is on a very slight hill, probably 5 - 15 degrees, but nearer the 5 degrees, and I park it nose up. Until I can get a clear picture on where the problem lies I'm currently leaving it parked in the garage or nose down. It hasn't happened since last Thursday, although it does get used at the weekend - we use the wife's car then.

I've been told by a friend who owns and runs a general car repair garage that his money is on the pre-heaters. I'd argue it can't be this because it sounds totally dead until about 20 seconds of cranking. If 1 or 2 of the heaters were faulty I would expect it to be lumpy since the cylinders that were OK would be firing. Any comments on this?

I also suspect it's air since the symptons are exactly what I experienced when I changed the fuel filter last Christmas. While I'm on this subject can you explain to me what's wrong with this logic - When changing the fuel filter, or removing the filter's retaining bolt, I would have thought the diesel that's in the remaining pipes, and pump, would have been sufficient to start the engine. Once the engine is running with this 'trapped' fuel it would keep the engine going long enough for the fuel-tank pump to replenish the removed pipes and filter. All I get is instant non-starting until it's all been primed again! Why does the fuel in the pipes and pump not allow it to even run for a few seconds?

Another correspondant to this message has suggested the rubber O-rings on end of the fuel pipe junctions could be allowing air ingress. I haven't checked these, but I suspect it'll be difficult with the naked eye to see any minor wear and tear. Changing them would be a preventative measure.

I've seen another possible clue when I checked the cavity where the fuel goes into the filter assembly. The pipe (from the fuel-tank pump) goes into a gauze (spelling?) filter. This cavity was bone dry when I opened it up. I would have thought it would have been brimming with diesel, unless internal fluid pressures drained it when I opened it up.

I think I've rabbited on for long enough, but I hope this answers all your questions.

John Hamilton
Scotland