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post #48 of Old 08-16-2013
Bombay Explorer 44
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Re: Runaway diesel

The two scenarios for engine runaways are

1 Pneumatic governor usually the single pipe. I have seen an old Mercedes boat engine with one of these. If the pipe breaks or the diaphragm fails they will runaway. You can pull the stop control and the engine will stop.

2 Any engine where the crankcase breather feeds into the inlet manifold. If there is any significant frothing of the crankcase oil and it passes through whatever trap is fitted you get a runaway. Pull the stop control and the engine will not stop you have to cut off the air supply.

If I got a runaway and could not get to the air inlet to stuff a rag in I would pull the decompressor if my engine had one. What ever damage would be done would be less than the catastrophic failure you get from a runaway. Worth doing a dry run to find if you need to remove something to block the inlet. Perkins diesels often have a filter that I would need to be removed before applying the rag.

While I have never witnessed a runaway that actually resulted in an engine failure that was catastrophic I have taken the breakdown truck to a Commer 2 stroke that had run away and so had the driver. There were bits everywhere and one of the pistons was embedded in a brick wall many yards away.

Last edited by TQA; 08-16-2013 at 06:15 PM.
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