fuel in the crankcase

Ricky Mac

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Joined
Oct 20, 2013
Messages
2
1984 Fisher Pontoon w/ 3.0 liter4-cyl Mercruiser I/O. Getting fuel in the crankcase. Engine was just rebuilt. Am told that the tank is above the engine and gravity causes an overflow of fuel and I need to shut off the fuel when not in use. This hasn't happened before, why now?
 

MH Hawker

Vice Admiral
Joined
Jul 13, 2011
Messages
5,516
Re: fuel in the crankcase

A hole in the fuel pump diaframe is know to cause that is car motors.
 

Fastatv

Petty Officer 1st Class
Joined
Sep 28, 2013
Messages
258
Re: fuel in the crankcase

If your running the correct fuel pump, then there should be a hose from the pump to the carb which is used to send the fuel to the carb if diaphragm gets a hole in it. If your getting fuel into the case, then I would suspect a float thats a little high, or a damaged float valve or seat. A shut off valve placed into the fuel line btwn pump and carb would do the trick, however, it would be a bandaid for the problem. Hope this helps. Rick
 

Fishermark

Vice Admiral
Joined
Oct 19, 2003
Messages
5,617
Re: fuel in the crankcase

I would go with the faulty fuel pump myself. As mentioned, a ruptured diaphragm can put fuel in the crankcase - but yes, if you have a clear sight tube - be sure to check it. If there is any fuel in the clear line, then you have a bad pump.

I would not suggest adding a shut off valve. Your tank should already have a anti-siphon valve in it unless someone has removed it. But even then, fuel should not be able to get past the float valve.
 
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