02 4.3l carb strange fuel problem

[H20Rat]

So the backstory. First time out this year since Sept. (Long winter!) Unloaded at the ramp, and the engine was more finicky than usual. Died idling a couple of times even. It died 4 times idling in the bay but seemed to clear out, so I just chalked that up to old gas. Cruised for about 15 minutes, and it dies again, and this time it won't restart unless I wait about 15 seconds or so. (And nearly immediately dies again.)

Luckily, it died in front if my own dock, so I was able to change the main fuel filter, same results. Had a neighbor tow me back, and during the tow I checked the fuel filter in the carb. Spotless. I also bumped the key with the fuel line off to see if the pump was good, and fuel shot across the engine!

Anyway, reattached the line, let the bilge air out, and restarted it. This time though, it didn't die, in fact I stopped my tow, and ended up boating for another two hours, anywhere from idle to WOT, not a hiccup.

Any theories? I don't like when a problem fixed itself. My only theory is that the fuel pump somehow either was stuck/weak, and when it was able to pump without restriction it freed up. (Or a air bubble in the pump?)

 

[alldodge]

Guessing
The carb float got stuck or antisiphon valve got stuck

Electric fuel pumps don't suck very well, so if there was a slight restriction it may have been starving for fuel until it got free

 

[H20Rat]

Update to the issue. Went to unload today, and it was a repeat of the previous above. (Although it never left the trailer this time!) Brought it back to the cabin and started troubleshooting.

Pulled the carb apart, it was spotless and nothing sticking. After reinstalling and having it repeat, I pulled the fuel line off and got a container to catch it. Started it up, and it pumped for a second and then stopped. Engine was running (at least momentarily) and not a drop of fuel coming out of the disconnected line! Electrical connector is clean/tight, so it has to be the pump itself. Replacement is on the way should be here Tuesday!

 

[alldodge]

Hope its the pump and not a restriction like the antisiphon valve

 

[H20Rat]

Hope its the pump and not a restriction like the antisiphon valve

I had thought about that also. Going to do some bench testing of the pump as well as seeing if I can test the fuel flow. Got a spare anti-siphon valve ordered, luckily I've got full access to the tank through a hatch.

 

[alldodge]

Can also stick a piece of gas hose into a 5 gal gas can and run it that way. If it runs good on the can then the problem is the tank, pickup tube or valve

 

[H20Rat]

Bench tested today and more confused than ever!

Tested the pump by itself, shot a stream of water about 3 feet up. (Although I can't be sure, I think it didn't spin the first time I had it on the battery, could have just been a loose connection though.)

Pulled out the fuel hose and 1 way. Spotless, and was easily able to blow though it. Also tested the pump, hose, and one way, shot water maybe 1.5 ft up.

Finally removed the fuel pickup tube. Again, spotless, not a hint of debris on the screen on the end, no obstructions.

So it is either an intermittent pump failure, or for some reason an intermittent electrical failure where it isn't receiving power, sometimes.

Still have a new pump and 1 way valve coming, and I might wire in a 12v LED on the power wire to the pump.

 

[alldodge]

might wire in a 12v LED on the power wire to the pump.

Your tracking it down, and that would be a good idea, or at least keep volt meter attached or test light

 

[H20Rat]

Your tracking it down, and that would be a good idea, or at least keep volt meter attached or test light

Based on a bunch of reading, lots from your older posts, this seems ALOT like the oil pressure switch issue. Cranking it gets power to the pump, and once it starts the pump no longer has power and it is running on the fuel in the bowl

Off to check that now!