Hey folks, since I'm in the middle of dealing with my little runaway (the joke I heard is that there is no such thing as engine
runaway... it's actually mechanics runaway when dealing with "overspeeding").
I was having a hard time getting a clear picture of the the why and how so I could diagnose the cause properly. There is plenty of info it is just scattered all over the place including here and several other sites.
This post is my own amature attempt at a diagnosis protocal.
My goal here is to try to give someone a decent one stop chunk of info that will help them solve the problem as cheaply and effectively as possible. Please chime in if you see any ommissions or problems
Based on various forum comments and conversations with mechanics this is mky best shot:
1. Make sure not to overfill oil
overfill can cause blow-by of engine
oil into the cylinder heads. Once (if) the overspeeding engine has been stopped allow engine to settle then check the oil level in the crankcase. Drain off excess oil as needed and while your at it change the oil if it‘s dirty. If the engine oil level is normal or excess has been drained try again to turn over the engine the following day.
2. Had the engine RPMs been fluctuating or “hunting” ; suddenly increasing then dropping again prior to the runaway? This could indicated either a partially clogged fuel filter
or bad fuel
line connection inhibiting proper fuel delivery
. It can also be a symptom of a screwed up injector that can become stuck open allowing fuel to spray uninhibited into the cylinder thereby causing runaway. In the case of those engines with the injectors racked together all injectors will be frozen in the open position. Let the engine cool down, check all fuel line connections, change the fuel filter(s), bleed the system, try again to see if the engine RPMs are still fluctuating. Next step will be to check if one of the injectors is having a problem. Remove each injector one at a time if possible and crank the engine. Each injector should pulse and not allow a steady stream of fuel. Replace/rebuild any defective fuel injectors and try the engine again. The threat of runaway should be incentive enough to attend to fluctuating rpms promptly. I knew it was fluctuating on my Perkins
but did not understand the importance of trying to fix it sooner than later.
3. The governor in the injector pump
has failed and the injection pump has to be re-built.