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Carb losing prime?

J

JJDebeers

Regular Contributor
A few weeks ago both motors quit while out for a cruise. First the starboard and then the port. In both cases I found that the carb bowls were dry, as there were no squirts from the accelerator pump when the throttle was pumped. I got the motors started by removing the spin-on filters/separators and splashing some gas down the carb throat. While removing the spin-ons I heard a "pssst" vacuum relief sound. I replaced the spin-ons with my on-board spares and limped her in at around 1,500 rpm because the motors would quit if I tried running harder than that.

Back at the dock I found that the rubber portion of the my pick-up tubes had completely collapsed internally. I have a single 220 gallon tank with a pick-up tube for each motor. I replaced the rubber, and was sure that I had found and corrected the issue.

This past weekend my starboard motor quit again after about 30 minutes at crusing speed (2,000-2,500 rpm). Again, I found that the carb bowl was dry, as there were no squirts from the accelerator pump when the throttle was pumped. Again I removed the spin-on fuel filter/water separator in order to pour some gas down the carb and heard a "pssst" vacuum relief sound when removing the spin-on.

I poured a splash of gas down the carb, replaced the spin-on with a brand new unit and the engine fired up. I limped it in at around 1,500 rpm in fear that the motor would quit again under a greater load.

My port seems to be fine after the pick-up tube replacement, but something is still causing me to loose prime on my starboard motor.

My tank vent is clear, and I'm going to check all lines and fittings on the starboard side. I have no anti-siphon valves, only manual stop-cock type valves. I don't think I'm sucking air, since I can hear that vacuum relief sound when removing the spin-on.

Could a fuel pump be the issue here? Anyone ever see a fuel pump work at low speed, but fail at higher speed?


Thanks,
JJ
 
No, and wouldn't account for that "psst" sound.

Something is collapsing and blocking flow into the separator. Either that, or the tube is a bit too long and is getting sucked against the bottom of the tank, blocking itself off. Try shortening it a 1/2 inch.

Jeff
 
Make sure to use the A-1 rated fuel line that has a red stripe down the side. It is rated for constant fuel contact with ethanol.

The tank fills or vent hosed could have collapsed also.

Look at my fuel tank replacement project I posted today. I have a pic of my fuel fill hoses collapsed. They looked perfect on the outside.
 
So I dumped the contents of my starboard water separator/filter into a glass jar. No water, but a lot of sediment and gunk came out. I then cut the filter open with a hack saw to inspect the paper element and found more sediment. The paper also exhibited some resistance when trying to blow air through it by mouth.

I think the sediment in my tank is the issue. I'm having the tanks cleaned and fuel polished on Friday. I'll report back with results.

Thanks,
JJ
 
Had the fuel polished today. This is what the first 2 micron filter looked like after the first tank turn-over. They turned the contents of the tank over about 3 times and used up 3 filters before the fuel looked clean.

I'm hoping this was the root cause of my issue.

Thanks,
JJ

tank crud.jpg
 
That'll do it!

Ethanol gas tends to stir up stuff like that that's been sitting happily on the bottom of the tank for years. Another reason to hate it and those who stuck us with this crap!

Jeff
 
The fuel polishing seems to have worked. She ran great this weekend with no stalling. I wouldn't be surprised if I go through one more set of fuel filters to catch any residual crap that the fuel polishing didn't get, but I think the issue is pretty much resolved.

If anyone is having these issues in New England let me know. I would highly recommend the guys that did this for me.

Thanks,
JJ
 
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