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post #26 of Old 05-11-2012
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Re: Runaway Yanmar 2qm15 HELP!

Originally Posted by dabnis View Post
OK, I think I have got it? If you used #2 piston for TDC the timing is 180degrees retarted. Every engine, gas or diesel, that I have worked on uses Piston #1 for TDC settings. Which means:

1. The real intake stroke becomes the power stroke
2. The real compression stroke becomes the exhaust stroke
3. The real power stroke becomes the intake stroke
4. The real exhaust stroke becomes the compression stroke

So what, you ask? The fuel is being squirted in on the intake stroke and eventually accumulates to the point of being enough to ignite on the compression stroke. As the fuel is not all being burned because of the mixed up strokes more accumulates and the engine starts to run away.

I think

Anyway the timing thing is easy to fix, let us know.

Paul T
Forgot the 3 to 4 second "breathing" thing. Could be that with the valve timing being so far off that on either the intake or compression strokes a valve is partially opening or closing allowing the intake or compression gases to escape very slowly, I think?

Paul T
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