Starts then stops seconds later? Help

[mwh2319]

Has been running OK. But then shut down after a few hours of motoring. Thanks.

[W2ET]

Restarts after the engine cools down?

Bill

[sastanley]

Hi mwh,
we are gonna need a little more info.

There are some cases were a motor will run 45-60 minutes and shut down, but will fire back up again after cooling off...this is often (but not always) caused by a failed(ing) coil that shorts out when it gets hot, but works again after it cools. Will the engine restart immediately or must it cool down? Can you confirm fuel and spark immediately after the shutdown? When it quits does it shut down like you turned the key, or does it struggle/sputter for xx seconds/minutes?? I think one of these scenarios is where W2ET is headed.

You could have some crud in the fuel tank that clogs the pickup after running for a while..when the engine shuts off the crud falls back in the tank. (A fuel pressure gauge in the fuel line would be helpful here...many of us have added one near the polishing filter just before the carb.)

Those are the two that first come to mind. Intermittent shut downs are hard to diagnose without some additional tools at your disposal, and details on how/when the shutdown occurs.

If you can provide some more details, I am sure we will have more ideas!

[mwh2319]

More details on shut down, thanks

Sorry, should have given more details before.

Will only start, and always starts, when I spray engine starting fluid in the flame arrester. Stops running when that runs out in a few seconds. I’ve gone thru Moyers unexpected shut down check list and it looks like a blockage in the carburetor main jet.

Will take the carb apart and clean it. I drained the fuel filter/water separator and found a lot of water and crud. Also a rather small amount of crud when I drained the carb of about a shot glass of fuel.

Thinking of adding a polishing filter between the electric fuel pump and carb, and a pressure gauge there also as suggested here.

And hoping not to complicate this too much, I noticed my late model 5 bolt carb does not have a scavenger tube installed. Just screw in plugs instead where it would be. Should I install a scavenger tube?

And the spark plugs look like they’re covered in dry black soot. Is running too lean causing this. I’ve had some luck in the past by putting in a fresh set of spark plugs. Should I adjust the carb for this?

Thinking there’s a lots of crud in the fuel tank due to neglect. How do I fix that?

Finally, I could do some photos and videos if that would help.

Thanks,
Mark

[ndutton]

It's certain your problem is fuel related and your comment that the fuel in the tank is fouled points to the reason. The carburetor needs complete rebuilding but it's important to get the tank cleaned up at the same time or you'll be pumping the crud back into the freshened carburetor and the problems will continue.

I am a fan of full monty repairs so if it were me I'd replace the fuel tank with new and be done with it. There is no downside to good filtration but I would not consider it a remedy for foul fuel. Solve the problem directly rather than work around it.

[sastanley]

Mark, You can safely remove the fuel with a hand pump thru the fuel gauge access port, if you have some place to put it (i.e. empty jerry cans) - If replacement is too much work, at least get the old fuel out, and then peer in the tank to see determine the status..i.e., if you can clean it, or replace as Neil recommended.

I replaced my glassed in alum tank many years ago, and replaced it with a poly Moeller tank. Wood support blocks (laminated with epoxy/glass) were glassed to the boat during the install..then I used the recommended clamps by Moeller to secure the tank. Now, if I have a big fuel problem I can't solve in the boat, I can remove the fuel, and with about 8 or 10 screws, the clamps are loose and out comes the tank (plus disconnecting the fuel lines). Anyway, my point is, I can now take the tank out of the boat (which I have done) whereas the OEM tank was glassed in the boat (the metal tank from 1977 sprung a leak in 2009, so that is why it came out).

Neil is also right, that there is no sense cleaning the carb 'til you fix the fuel delivery problem.

One more thing, (edit, OK two more.. ) make sure the o-ring in the deck fill is in good shape...that can allow rain/sea water, and crud into the tank...In reality, it is the ONLY place it should be able to sneak in, unless you got an extremely bad batch of fuel.
Those little $10 orange transfer pumps at Walmart/etc. work surprisingly well, and will empty the small tanks in our boats pretty quickly. My challenge has been making the hose end in the tank rigid to get all the way to the bottom (which is where all the crud and water is anyway). My most successful trick so far is GOOD duct tape, and tape the tube to a plastic garden stake...the duct tape adhesive will hold together long enough to empty the tank and the stake helps you get the hose all the way to the bottom, and should be small enough to fit in most of the tank openings. (i.e., if your boat has the fill straight down into the tank.)

Good luck with your plan and keep us posted.