mystery fuel line blockage

[Home Cookin']

last weekend the motor (150 hp) started acting stupid--dying down like running out of gas; when pumping the bulb it would stay soft or even collapse and not recover quickly. Then it would get gas and run fine for 5 minutes or so. This was after about 3 hours of running fine. Hairy crossing the shipping channel in the harbor!

So I figured fuel pick-up but I was also hearing a possible air leak. I started in the motor with its filter--OK, and replaced the water seperator (about 50 hours and 7 months on it). replaced the bulb and the line from the tank. unscrewed the tank barb and it was OK; anti-syphon valve seemed OK. I was hoping I wouldn't have to pull up the sealed deck to get to the pick-up tune; the floor hatch is just an inch off so you have to. But the problem peristed.

I pulled up the plate, unscrewed the pickup tube fitting. no apparent blockage and it held the fuel in it like a soda straw. reinstalled, resealed, boat seems to run fine.

So if it was an air leak, would that cause the bulb to stay collapsed when you squeeze it while running?

If it was a blockage (usually a piece of tinfoil from the top of a stabil bottle) I guess it's still in there, lurking, waiting to get me one night in bad conditions?

there wasn't any way to look into the tank through the pick-up hole and the fuel gauge hole is a couple feet away (80 gallon tank).

thoughts? Or do I just keep my fingers crossed?

 

[robert graham]

Re: mystery fuel line blockage

Not much worse than a random, inconsistent problem that won't repeat itself....how's your fuel pump?, partially plugged filters/screens? You're not gonna feel good crossing the harbor until you identify and fix it! Good Luck!

 

[Texasmark]

Re: mystery fuel line blockage

Collapsed bulb as you probably know means the fuel pump is sucking on a closed container and creating a vacuum in the process. You touched upon everything but a clogged pickup screen in the fuel tank.

I used an after market product once that was marketed to absorb water in permanently installed tanks that usually don't get completely emptied over time and can accumulate water. I was blasting across a pretty rough lake one day and the engine quit. In short, when I removed the fuel line at the engine quick disconnect hose barb, I saw this milky looking goo all over and in the barb. I squeezed the bulb with the end of the hose open and squirted out several inches of this stuff. It had totally clogged my fuel line.

The same thing could occur in a fuel tank and depending on the dimensions of the fuel line pickup screen and the size of the blob it could smother your fuel pickup. Your trouble shooting techniques could have dislodged it only to return an plague you sometime in the future.

You had concerns about being haunted with something, well this is a distinct possibility....at least it explains one way you could have fixed your problem without finding a smoking gun.

HTH,
Mark

 

[Home Cookin']

Re: mystery fuel line blockage

yes my fuel pick-up screen was clean, so I don't think it was a "goo" but probably a solid. If it were just water in the tank causing the problem, it would not have affected the bulb, right? So that's why I suspect a solid, still lurking.

But odd that it was intermittent; I can't picture a solid going on and off the pick-up. I need to give it a longer test run to be sure, but while I was trouble-shooting and fixing, I'd run it after each step and the problem recurred each time, after a couple minutes running. Worse at higher speeds, which indicates partial blockage or small air leak that only showed at higher pressure (I guess?)

 

[robert graham]

Re: mystery fuel line blockage

Maybe the O-ring in your fuel line quick-disconnect on front of cowl allowing an air leak?...

 

[Sea Rider]

Re: mystery fuel line blockage

Disconnect quick connector from engine, maintain connector's pin pushed all the way down, squeeze bulb several times to purge line in proper container, repeat several times and see if any debris exits. If the fuel flow passes and exits in abundance through line, seems other issue, probably as stated by RG, connector's o'rings worn out. Replace if easy to find. Some engine manufacturer's don't sell them as spare parts, sells complete connectors, which is a real crime!!

Is it a standard one piece cover black hose, one time bought a hose that was double cover, with time the inner cover went to pieces and blocked bulb, the issue was discovered while purging line.

Happy Boating

 

[Chris1956]

Re: mystery fuel line blockage

Did you check the tank vent? A collapsed primer bulb indicates a blockage in the fuel line from primer to tank, or a vacuum condition in the tank. It would seem that you are in the presence of saltwater, as well. This makes it more likely, as corrosion can clog a vent quite easily.

 

[Home Cookin']

Re: mystery fuel line blockage

thanks for the suggestions.

The lines are all hard-connected; no quick connects like on smaller motors and everything seems OK in the cowl.

PLus with the bulb staying flat (it doesn't suck down but when the engine is messing up it doesn't recover quickly from squeezing) I suspect it's upstream from the bulb--which is 4' of hose (replaced as part of repair), tank barb w/ antisyphon, then pick-up tube.

Good suggestion on the vent. I have a fill cap with built-in vent, and the vent hose is about 1" diameter. And by the fuel guage I'd say the tank had 30 gallons of air space in it. So I didn't suspect that direction. I haven't resealed the deck plate, waiting for more test runs, so I can pull it and check the vent attachment and path.

 

[Philster]

Re: mystery fuel line blockage

Can't the bulb be the culprit?

I've got a mental note that they ain't like the old ones that were more reliable.

 

[Home Cookin']

Re: mystery fuel line blockage

Can't the bulb be the culprit?

I've got a mental note that they ain't like the old ones that were more reliable.

replaced that, too

 

[LongLine]

Re: mystery fuel line blockage

I'd replace the anti-siphon gizmo. (maybe just for giggles & grins, but the ball is known to stick once in a while)

Tom B.
(LongLine)

 

[JB]

Re: mystery fuel line blockage

Had one like that on my son's boat years ago. Turned out that when the dealer replaced a cover on the small bilge he pinched the fuel line.

 

[gimp99]

Re: mystery fuel line blockage

Don't know if you have one or not but a small air compressor is a good investment.Disconnect your lines and blow them out. If the lines are clear you will hear the air hiss. and even if there is a small blockage the air pressure will usuall discharge the culprit. If you are not into getting a decent size one check out harbor tool and freight on line or locally if you have one where you live.A cheap hundred PSI pancake compressor is around fifty bucks.Has about a 2 1/2 gollon tank and is small enough to fit anywhere. Attachments for it are cheap too. And for those who say it is a cheap Chinese compressor, your right. But if it is not in use everyday it will last a very long time and is substantilly less then really good ones. And it is great for pumping up low trailer tires. The one guy is right , a collapsed bulb is under a vacuum and clooged tank vent is usually the culprit.. If you are carefull fueling it is not that easy for debri to enter the tank. If you need comformation just run the boat and see if the problem occurs agin if it does just loosen the tank fuel cap. If it is the vent the bulb will spring back to shape

 

[GTS225]

Re: mystery fuel line blockage

Is it possible to hook up a portable, 5-gallon tank in place of the in-deck one? If the problem repeats, then you've at least removed the permanent tank from the equation.

Roger

 

[Home Cookin']

Re: mystery fuel line blockage

thanks, all. I ran it Saturday for a couple hours and it was fine, though I didn't get up to higher speeds much due to conditions (small craft advisory so I took their advice and went out in a small craft).

Think I might get a new anti syphon, and switch them out; keep th eold one as a spare.

Didn't think to open the fuel intake; will do next time to confirm/eliminate the vent.

Hooking up a remote tank is difficult due to no quick releases (which also eliminates a typical culprit) but with the bulb acting up I feel certain it's upstream--which is the tank.