Fuel problems

[Seif911]

Good morning all,
I am not really sure of my fuel problem. I think there were multiple issues. The boat runs great at idle speed, every time I hit the throttle, both engines would die. It happened 3 times. I found that the vent hose went from the gas think top, straight to the bottom of the boat. I have rerouted that.
I also found that the fuel filter on the port side was full of water, varnish, everything but good gas. I have refueled just before that with 97 gallons, I also pulled 2 gallons of water out of the old gas when I put the boat in the water. I just changed the fuel filter on the port side so hopefully that will be good.
The starboard side, every time I let the boat sit too long, it is hard starting, to the point I have to dump gas down the carb to get it going. I pulled the fuel filter and there was nothing in it but some rust....I mean not a drop of gas. Do you think that before I if Ed the vent problem that a vacuum was created in the tank and it pulled all of the gas back in? Would a new anti siphon valve keep the gas from going from the lines back into the tank? Nt sure what the issue is here or how to fix it.
My guess would be to get a new anti siphon valve and maybe a fuel bulb inline just in case. Thoughts?

[waybomb]

No, vacuum can't pull gas out of the fuel bowl. You have the leaky quadrajet issue. Search the net. They need rebuilding.

Have you also checked your timing, to spec? I tend to check timing after all the advance is in or total timing. Timing specs are usually for a set low rpm. But you have no idea what is going on after that. So I disconnect the throttle cable, and manually hold the r's at 3200rpm just to make sure it's all in and time from there. Then as I let off the throttle, I watch to see if timing backs off as throttles are released.

Your engine spec book should have what the timing is at idle (maybe 600rpm?), and and full advance, and at what rpm full advance should be in. Check it all.

[Seif911]

Hey Fred,
The weird thing is that the big canister fuel filter, that is below the carb, was totally empty. That kind of shocked me. There are only a few things before the fuel filter, possible a fuel pump issue? I am just not sure. I mean gravity could not pull the gas out of this upside down canister? I looked up the quadrajet issue, I might have that problem too but that could not pull the fuel up from this fuel canister. I don't get it.

[waybomb]

Check those anti-siphon valves.

For the vent, if you can get to the connection at the tank, you should be able to disconnect it there and blow through the hose with no resistance.

[Seif911]

The port engine I believe might be fixed but I haven't tested it yet. The starboard engine, I'm not sure. I blew through the vent hose and that is now good. I pulled the anti siphon valve and it works as it should. So between the gas tank and the carb is just the fuel pump. It almost has to be 1 of maybe 2 problems. I think I will replace that.

However, Fred, I suspect that those plugs on the quadrajet may also be a problem. It looks like a lot of people a actually just pull the carb, turn it over and tap the plugs back in, if they are still there.

So the plan...swap the fuel pump. Put the anti siphon valve back in. Test both engines at full throttle. Wait 3 days and see if the starboard engine is hard to start. If it is, then pull the carb and fix the plugs.

[waybomb]

Tap the plugs back in, and mix up some JB Weld and help keep them in place.

[Seif911]

Good Morn' All,
So I was digging on the Internet and seen something that sparked a thought. The vent I was playing with was on the back of the fuel tank. When you hit the throttles, the boat goes into a angle and the gas rushes to the back, thus not letting the vent work correctly. There must be a 2nd vent at the front of the tank! I have not looked.

So I dug through my pics and there it was on the side of the boat by the water drains, and it almost looks plugged. I will have to investigate this one too, maybe it is my issue?

image.jpg

[CYO Admin]

That could be the problem. If you have a water tank and holding tank, they will also have a similar vent in the hull like the one in the picture.

[Seif911]

Hmmm...so it may not be a fuel vent? Uggg...I will find out tonight. I am hoping to go fishing if the boat works. They are catching tons of fish right now. We'll see.

[Seif911]

So I fixed the old fuel problems and found a new one.

I replaced the anti siphon valve and that totally helped the starboard engine. I replaced the filter element on the port side and that seemed to help that engine. I also rerouted the gas vent so it goes straight out and that helped out both engines from creating a vacuum and stopping the fuel.

Of course...the fuel canister on the starboard started to leak. I will replace both sides with a new water separator/fuel filter. Yay!