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Posted: Fri Jun 11, 2010 8:38pm

Post Subject: erratic engine idling

i own a springer 30ft with 2002 volvo penta diesel,with engine idling at 700/750 occassionaly the engine speed picks up to 1000+ & to bring it down i have to pull the stop control out. any ideas?

Tony-B
Tony-B

Posted: Sat Jun 12, 2010 9:25am

Post Subject: erratic engine idling

I am not going to be much help here because I think this one needs some direct experience of the 2000 series of engines so I hope readers can help. First of all I am almost sure this injector pump uses a mechanical governor. If it turned out to be hydraulic (and the on-line manuals fail to describe the pump) then it could well be fuel starvation. I know this sounds odd, but that is what hydraulic governors tend to do. Although I doubt it will make nay difference it would not hurt to change the filters, bleed the system and make sure no air is being drawn into the fuel lines etc. A mechanical governor essentially balances a spring that you tension withe the throttle against a pair of centrifugal bob-weights. If the engine slows because it has come under load the spring overcomes the centrifugal force and move the control rod/rack to have more fuel injected. If the engine speeds up the centrifugal force overcomes the spring to reduce the fuel injected. I can see nothing here that would give those symptoms. However there may be two springs involved, a large one and a small one. The small one only coming into play at idle. I suppose a broken spring could jiggle itself around so the coils pass through each other so shortening its length but why it should return to normal when the stop is pulled in beyond me. The stop only drags the control rod to the "no fuel" position so the engine stops. From what I can see , and this would be exceptionally unlikely, the most plausible explanation is that the engine is getting hold of fuel from another source. This could be gas escaping into the engine room, fumes from some kind of cleaning solvent, fumes form the crankcase (indicating a badly worn engine) or oil mist caused by an overfilled sump. The latter can occour if fuel leaks from the lift pump or injector pump into the sump. Feel and smell the engine oil. If it is thin and smells of diesel and over the maximum on the dipstick it could well be a fuel leak. Drain the oil and refill & see what happens. If the problem seems to have gone then it is almost certainly an internal fuel leak which needs tracing otherwise in time the problem will come back. Sorry not to have a definitive answer. Tony Brooks

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