Hi all,

Ive had a baffling fuel issue. 1983 F150 2wd 302, c4 combo. It was a family members vehicle that they had for 16 years. I drove it in high school and had no problems with it. about a year ago I ended up with it after it started having some issues.

It was hard starting after it had sat for a month or so. Put a fuel pump in it, make that two, since the first one was bad out of the box. Next issue was it would die on up hill or down hill and sometimes flat ground. More of a nuisance since I would just pour gas down the vent tube and it would start.

I figured the pump was losing prime and had a cheapo pump. I pulled the box off and replaced all the rubber lines, pulled the senders and the tanks are clean as can be and the rear tank was dry, so no selector valve problems. Installed a canister filter on the frame rail with a 3/8" brass ball valve(service reasons) after the selector valve and everything seemed fine. Truck would start easy.

A week or two later the fuel pump finally quit and I put the summit racing billet pump in and everything was fine again.

Tonight I went out to move it after sitting a week and either the fuel pump lost prime or isnt pumping the truck will run off whats in the carb and die.

Sorry for the long post but this has been baffling.

Thanks, Corey.

 

Wow, my legs get reallly stiff after just an hour or two of sitting. There's no way I could last a week.

Back to your truck:

i wonder if your fuel tank isn't venting properly and a vacuum is building up. Does your truck have a common vapor recovery system for both tanks?

Duplicate the fault conditions as much as possible for troubleshooting. Drive the truck like you normally do and then let it sit for a week. Make sure you move around, though. Then enlist a helper. Crawl underneath and watch the gas tank while your helper cracks open the gas cap. Listen for a rush of air at the filler neck.

Here's why you're in the dirt watching the tank. You'd hear the same rush of air whether the tank had vacuum or pressure built up. Pressure would actually be beneficial, as long as not excessive, as it would help feed the pump. Vacuum is just the opposite, and will make it harder for the pump to draw fuel. So watch the tank to see which is which as the cap is removed. If the tank collapses slightly, it had pressure. If the tank expands, then you were fighting a vacuum.