Fuel tank issue?

[mkiefer]

I have a newly rebuilt chevy 350 in my Caribean. The motor runs great. Until one day Im driving along and it starts to die. It wont restart. I have duel fuel tanks so I switch to the other tank, it starts and Im good. After fooling around with it I can reproduce it consistantly with this fuel tank, when the fuel level is under half, maybe to 1/4. I can run on that tank for about 10 minutes and it starves out. Switch to the other tank and it runs fine. Then I can switch to the 1st tank again and it will run for 10 minutes again and starves out again. Every time. I tried popping open the cap thinking it might be a vacumn, nope. Any ideas what could cause this?

 

[GA_Boater]

So when the bad tank is full, it runs fine until somewhere between 1/2 - 1/4 empty.

A couple of things. A bad gauge sender and it isn't as full as the gauge says it is or the fuel pickup in the tank doesn't go to the bottom of the tank.

I hope you can access the sender and pickup

 

[ajgraz]

Could the problem tank be half full of water?

 

[GA_Boater]

Could the problem tank be half full of water?

No, the water is sucked from the bottom so a full tank wouldn't run OK until the tank is 1/2 empty. It wouldn't run at all, not even the 10 minutes.

 

[Yegboats]

Maybe an antisiphon valve problem?

 

[ajgraz]

No, the water is sucked from the bottom so a full tank wouldn't run OK until the tank is 1/2 empty. It wouldn't run at all, not even the 10 minutes.

Duh, yeah the water would be on bottom. Was thinking though that the 10min could be running on whatever fuel remained in any separating filter, fuel lines, etc.

 

[Bondo]

Ayuh,.... Another possibility is a cracked diptube,....
It would suck air, insteada fuel from the bottom, whenever the tank level gets down to the point of the crack,...
Pull the outlet fittin', 'n you can check the diptube, 'n the anti-siphon valve,....

 

[jimmbo]

I think Bondo hit the nail squarely on the thumb. I suspect the fuel pickup is near the rear of the tank. If so, as a test, try running in a very bow up attitude(non planing). That would keep the rear part of tank completely wet. If engine runs without staving until the bow lowered it backs up the leak theory