# Gas in oil sump Briggs and Stratton Engine 21HP



## Tonyclo (Aug 2, 2015)

When running gas is getting into the oil sump on B&S mower engine. This does not happen when the engine is not running. Have fitted a new carburettor. Compression both cylinders is 160PSI cold and 150psi hot. Spark plugs both show clean. Starts and runs perfectly. I can't figure out what's happening. Any ideas?


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## SpywareDr (Jun 15, 2013)

Welcome to TSF! :smile:

How did fuel get in my engine oil and how do I fix this

?


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## Tonyclo (Aug 2, 2015)

Thanks for the welcome. My problem is that the fuel gets into the engine when running - not when stopped as outlined on the B&S site.


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## SABL (Jul 4, 2008)

How old is the engine?? B&S fuel pumps are pulse type driven by pressure oscillations created in the crankcase.....when the piston goes up and down. Check for a broken diaphragm in the pump that can leak fuel through the vacuum tube into the sump area.


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## Tonyclo (Aug 2, 2015)

The engine is 2006 but I think you are onto something. I am going to buy a new pump - it can't hurt and I think it may solve the mystery. Thanks. I'll keep you posted when I get the new pump.


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## SABL (Jul 4, 2008)

Good luck......hope it solves the issue.

I have an '04 but it's a Kohler and hasn't had a fuel problem yet.....knock on wood.


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## Tonyclo (Aug 2, 2015)

You nailed it! Installed a new fuel pump and problem is gone. Thanks a million.
Tony


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## SABL (Jul 4, 2008)

Tonyclo said:


> You nailed it! Installed a new fuel pump and problem is gone. Thanks a million.
> Tony



:thumb:

Thanks for letting us know!!


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