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Old 08-08-2022, 12:09 PM
Grappler Grappler is offline
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fuel leak from mechanical fuel pump

Recently I noticed a gasoline smell from the engine compartment after shutting down the engine, after it had run for an hour or so.

I noticed some fuel on top of the mechanical fuel pump.

I couldn't tell where it was coming from, but replaced the short piece of fuel hose from the fuel pump to the carburetor. This didn't fix the problem.

I've noticed that the leak doesn't happen while the engine is running, and it doesn't happen after shutdown IF I keep the engine compartment blower running and keep the engine compartment door open, till the engine has cooled down.

After several outings, I still haven't had the right timing to see where the fuel is leaking. It either doesn't leak, or it leaks while I'm not watching it.

It seems to leak only about a tablespoon or two, but I know this is still a hazard and needs to be fixed. A couple of times there has been enough to run out of the depressions in the top of the fuel pump and drip down the sides.

Any ideas on the cause and the fix? I'm headed up to the boat tonight and will probably remove the fuel pump to inspect it.

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Old 08-08-2022, 12:42 PM
Dave Neptune Dave Neptune is offline
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I think perhaps your "diaphragm" may be compromised and the "hole" to drain such into the oil is plugged, perhaps by sealant.

Can you smell fuel in the oil at all? If so a rebuild of the pump is in your future, luckily it is pretty easy to do. The removal and replacement is more work and depending on your accessibility it may be a PIA.

Another question since the pump is not supposed to leak anywhere but a poor fitting or into the oil. So if there is anything above it in the fuel system I would suspect that first.

Dave Neptune
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Old 08-11-2022, 03:33 AM
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Theo Lewis Theo Lewis is offline
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Agreed a removal and rebuild. Or maybe a replacement is in order. 40-50 years is a pretty good run. When I purchased my boat it had exactly the same problem. Looking back it was a huge fire hazard. The p.o.’s had neglected the engine badly. The fuel side was covered in a thick slurry of grime, oil and gas. Upon removal of the fuel pump it was apparent the sediment bowl had multiple pin-holes as well as a failed gasket. In addition the gaskets in the pump body appeared… not-so-fresh. The pump was basically spraying a mist of gas everywhere whenever it ran. Blower managed the smell pretty well like you describe and somehow it still ran. I ended up removing all from the intake ports and back to the tank then reassembling clean with new gaskets, carb, a Racor filter and finally swapped out the mechanical for the Facet electric pump kit. Entirely pleased. I’ll take anything apart and try to fix it but when it comes to gas, replacing with new seemed reassuring.
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Old 08-22-2022, 12:58 AM
Grappler Grappler is offline
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Thanks for the feedback guys!

It turned out that the problem was the filter screen on top of the sediment bowl. It must've slipped sideways the last time I removed/replaced the sediment bowl, and overlapped part or all of the width of the rubber gasket on top of the sediment bowl.

When I ran the engine last week, after shutdown I pushed lightly on the side of the sediment bowl and gas spurted out. I removed the bowl and noticed the misalignment, and was careful to get it aligned before reassembly. I pushed it upward so it centered and stuck in the cap, then raised and secured the sediment bowl.

I've tested it three times since then, and have no more leaks.

The strange thing was that before the fix, fuel got over on top of the fuel pump and even on top of the sediment bowl cap. It must have been spraying pretty forcefully, but briefly.

After the fix, I realized that the first time I noticed the leak was on an outing soon after I had removed and cleaned out the sediment bowl.
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fuel pump leak

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