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My fuel pump is leaking oil. Motor is a 17.5 Briggs and Stratton (31F707 0112 E1) on a 17 year old JD L100
Motor sounds and runs great.
I just replaced the head gasket last night as I thought that was the problem. Checked the oil level, tube from dipstick to fuel pump, hose from crankcase to carb (no obstructions or cracks).
Compression test reads 115 PSI
Only unusual thing I saw was some damage to the head from a loose screw. About 3 weeks ago the throttle control was working. Found that the screw from the throttle valve was missing. Now I know that it was sucked into the cylinder and banged around a bit causing the damage. I smoothed any high spots and the gasket area looked to be fine.
Everything else seems to be fine, motor is happy but I have the fuel pump leak. Hoping you have a suggestion.TIA

What did the piston look like?

Scrubcadet10 said:

What did the piston look like?

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The outside ring was banged up in a similar fashion, center was fine. Cylinder walls have no damage.

Then you may have struck ring(s) from the damage if it is like the piston I had to replace due a shattered valve seat.

Wouldn’t the positive compression test suggest the the rings, piston and head gasket are good?

Well it depends how bad the ring got pinched. Even the top ring landing can be cracked and later break off and there is definely a lot impacts present. Personally I wouldn't trust that things are find just because a compression test says it is okay as you may only have partial compression as these engines uses an ACR which decompresses the cylinder below 90 psi in the first place. Plus if the ring is pinched and the cylinder is taper or ovaled the ring may not be sealing in lower part of the compression stroke
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I had engines with great compression to have problems in the lower part of the stroke. I even seen engines to pass leak down tests to be bad in lower part of the stroke. With OHV engines it is simple to test the complete stroke with a leak down tester by disabling the valve train. Last year I had a Tecumseh engine that had only a 10% leak down result at top of the stroke where most tester test but when went to middle to bottom of stroke ti went to over 60% leakage. Pulled the engine apart and sure enough the cylinder was that tapered and ovaled.

Now of course my shop rep is on the line too as I warranty my workmanship for 30 days; although, sometimes, unforeseen problems can occur.

JoeAq said:

The outside ring was banged up in a similar fashion, center was fine. Cylinder walls have no damage.

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That area of the cyl head is called the quench area. The same for that area of the piston. From the looks of that head, i'd say you have a stuck top ring at some place on that top ringland, letting compression leak by, causing too much crankcase pressure. Engine problems will follow!

Thanks for the suggestions! This is my first time taking this (any) engine apart. I'll figure out how to get the piston out and check the rings.