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post #16 of Old 07-02-2013
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Re: Fuel in oil - where to start?

Originally Posted by Omatako View Post
IMHO it’s not the carb. If the carb was being so overwhelmed by fuel line pressure that it is contaminating the oil then that engine would run very badly or not at all. It takes very little extra fuel to flood an engine and it takes a huge pressure to overcome a needle and seat and bypass into the full float chamber.

If the needle and seat is dodgy, the engine will also run badly or not at all and the engine would definitely not start if there was enough fuel percolating into the cylinders to run past the rings into the crankcase. That's a really long shot as far as I'm concerned.

If you have a mechanical fuel pump on the side of the engine I would bet a considerable sum on the diaphragm being torn and allowing fuel into the crankcase. Start there – take the pump off, open it and closely examine the diaphragm. It will still pump even though it leaks fuel.
From earlier posts:

"Are you running the fuel line thru the old mechanical pump?

I have seen this done and if the pump diaphragm leaks AND the drain is blocked [ painted over ] then fuel finishes up in the sump. "


" fuel line is direct...tank -> pump -> regulator -> carb. "

Another thought, if it is an updraft carb I would think fuel would have a hard time flowing past the float and into the manifold? As Omatako said, if it was getting that much fuel past the float valve it would be running extremely rich and rough?

"Regulator"? maybe not working? Either way, it looks like the fuel is draining into the pan or is being ingested through the carb? Maybe try a gravity fed temporary fuel container directly to the carb, by passing the pump? An outboard gas can with a long hose from the cockpit to the engine should be fairly safe?

Paul T

Last edited by dabnis; 07-02-2013 at 12:58 PM.
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