Questions about fuel pump

[mattsmall1972]

One of the things I've noticed on the engine is that it seems that there's always been a bit of oil on the top of the fuel pump of my 1978 OMC 2.5L Stringer 400.

So today, I'm doing a water trial and the boat's running terrific - it's not overheating (I've had problems with this recently) and it's smooth and fast. However, after a few minutes of running, it "chugs" momentarily but keeps on going. After a while longer, the "chugs" appear more frequently and for longer durations.

I bring it back in. I'm still having electrical problems and my tilt won't go up, so I take off the engine cover to look at it. There's oil splashed everywhere on the side where my fuel pump is. I take this in as another thing to fix on this machine.

On the way home, I realize that the chugging and the oil splashes could probably both be tracked down the same thing - the fuel pump. So here are my questions:

1) Is it normal for oil to be in the fuel pump?
2) If oil is indeed leaking from the fuel pump, this could be an indication that it's going and that the chugging is the result is either it failing to pump or oil being in the fuel.

Thoughts? Anything I'm missing?

 

[mattsmall1972]

Re: Questions about fuel pump

OK... I went out and took the fuel pump off this morning and inspected it. The first thing is that I don't believe it's oil that was splashed, I think it was actually gas. It's not slick like oil although it is brown in color. For reference, I have a new gask tank and fuel lines leading up to the fuel pump.

One thing I did not realize is that this fuel pump has a filter built into it. The cover over the filter was loose and is likely the reason for the splashing.

The pump appears to work properly, but there is quite a bit of rustm on the inside, so it's going to be replaced.

What I'm thinking now is that when the pump splashed the gas, that allowed an air pocket to form and caused the "chug".

Thoughts?

 

[mattsmall1972]

Re: Questions about fuel pump

I realize that I'm responding to myself but for anybody that's reading this..

My initial suspicion was right, the fluid was indeed oil that was splashed on the engine. But it turns out that it was not coming from the fuel pump, which would have been weird.

I took the fuel pump apart and cleaned it throughly. There was a lot of sediment built up over time and it really needed this. However, the rubber all seemed to be in excellent condition, so I put it back together and back on the engine. This time, the filter cap is very tight.

I hooked the hose up to my nifty sterndrive hose adapter and started the baby up. It took a minute to get the gas back in but it did start up and stayed running, so now I know that the fuel pump is working properly.

However, I could see clearly that oil was still coming from somewhere. I shut the engine off and started poking. It seemed clear to me that oil was emanating from the 1) distributor and 2) the coil. Realizing that I'm insane, I shut the engine down and pulled the wires from both, where the oil seemed to be coming from. They are really clean. I cleaned the excess oil off from everything and start up again. This time, I see it coming from the vicinity of the oil pressure sending unit, and then I see the spray of oil coming from the same area to the coil and dist. cap. Ok, so I'm not crazy anymore.

I take off the oil pressure sending unit and it's got an "extension" to the hole in the motor. It's this extension that is the source of the leak and so I replace the part with some pipe fittings at Lowes.

So, start the engine and and it purrs, no oil leak, no fuel problems, so we take it to the lake for testing.

It runs great. No overheating, no chugging, it gets up on plane in a reasonable amount of time. This is the first successful trip we've had.

What's left is to replace one of the tilt solenoids (the up soleniod) because it seems to have gone bad, and fix the lights. I would like to adjust the throttle no make it more sensitive, and there might actually be a little more engine than what I saw today.

One important item of interest... the oil pressure gauge was reading very nice. Of course, this thing is 30 years old, so I'm going to get one of those little gauges like on a motorcycle to test it out to be sure it's good. Wish me luck, I really don't want to pull the engine.

Thanks for your rapt attention.