Oil Fouling

[davespurlin]

Trying to tune out a 1956 Johnson 10 hp Qd-17 that has been converted to a fuel pump. I’m seeing bubbles in the fuel line from pump to carb I let, which I know is an issue, but my question is can the bubbles cause the engine to oil foul the plugs?

[garry-in-michigan]

I don’t think so. Any bubbles would settle out in the float bowl (or filter bowl if so equipped.) A leaking float inlet valve would cause it to run too rich. Or a leaking pump diaphragm . Just guessing . . . 😕

[amuller]

Is this continuous or just after connecting the hose and starting up? To me, continuous bubbles suggest an air leak into the line/connectors. Are you using a standard OMC metal tank? There are a few O rings in the setup that might want changing.

If you can see bubbles you must be using translucent vinyl hose? I doubt the fuel mix would be influenced unless you have a situation which is *mostly* bubbles and not much liquid.

[davespurlin]

Yes, I do have vinyl tubing from the pump to the carb. Is that a problems?

[auldscott]

Bubbles should not cause oil fouling. Running too rich, using too much oil, or using the wrong heat range plug can all cause oil fouling.

Vinyl tubing: it will soon shrink and harden. Many times it will start to leak at the connectors. If you want to use translucent tubing, the Tygon polyurethane (Tygon is also applied to vinyl) holds up pretty well. It’s kind of translucent yellow-green.

[jerry-ahrens]

Is that an aftermarket fuel pump you have there? FYI, I’ve had several fishing motors come thru my shop that have had one of the ”cheap” Ebay, Amazon, etc. fuel pumps installed on them. On the ones I’ve seen, they all leaked at the seams. I tried an OMC fuel pump kit, but no go.. the gaskets and diaphragms won’t fit. I also noticed the check valves are junk. I think your better off buying a NOS fuel pump off Ebay.. that’s what I’ve been doing. I’ve found some pretty cheap. I had a V6 come in the other day, (with dual fuel pumps) and that one lasted about 2 years before it crapped out. I had to replace them with NOS OMC ones. I myself, was curious if these cheap pumps were worth anything… my conclusion is, no!

[davespurlin]

Thanks for the response, Jerry. Yes, it is an eBay purchased pump. It’s brand new and wasn’t cheap so I was not expecting to have issues like that from it. The thought crossed my mind to try a automotive electric pump controlled by a inductive relay on a spark plug wire. Ever seen anything like that? I know it won’t fix the check valve issue, but wonder if a coating of silicon sealant around the seams of the pump would help.

[garry-in-michigan]

If it is seeping fuel mix the silicon won’t stick. Surfaces must be clean and dry, no trace of oil. . . 😉

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