So I've been having this same problem for almost 6 months and still can't figure out what is happening. I have a 1977 Ford F150 with a 302 Automatic. It runs great for a good 20 minutes and then it starts to stall. I have changed the gas tank, brand new carburetor, new ignition module, ignition coil. When it stalls, it almost feels as if the carburetor is starving. Reason I changed the carburetor, it did it with the old carburetor on there and does it with a brand new carburetor. I hope someone has something they can add to my search, next up is changing the fuel pump, which I should have done when I changed the gas tank.

Thanks
Daniel

 

sorta sounds like it could be vapor lock. When you changed the gas tank, did you use the kind with the vent hole in the top, or not? Is your gas cap the venting kind, or not?

 

maybe cam lobe is worn and not pushing on fuel pump hard enough. had it happen once it been so long ago i dont remember if it quite all at once or was hit and miss.anyway i welded a beed on the fuel pump arm and it worked fine. and i carried an electric pump for back up ever since.

 

Next time this happens pop the hood and check two things.

1) Does it have spark?


2) Do the accelerator nozzles squirt fuel?

.

 

The next time you start it ,remove the gas cap and see what happens. If it keeps running the you may have a venting problem,wrong cap maybe.

 

I've had this problem on two different truck caused by similar situations. First truck was a partially clogged fuel filter. It allowed enough fuel to get buy to run the truck for a bit but not enough to do much more than that. The other truck was a clogged fuel line right after the tank and a clogged pickup tube. This one would allow the truck to run for quite a while and then it would die out. If I let it sit for 20 min or so it would be able to pull enough fuel through the clog to run for another 30 or so. Many carb/filter/fuel pump/gas tank changes later to get that one fixed.

I would by-pass your fuel filter (or just change it) and I would blow air down the fuel line from after the fuel pump to check for a clog. This may blow a bunch of stuff into your tank so be careful.

Good luck

 

Thanks everyone for ya'lls input, I will definitely keep checking for all of the above again. I really want this truck to run nicely, but don't we all.
Daniel

 

My truck had similar sounding issues. I would have sworn it was starving for fuel. I replaced the magnetic pickup in the distributor and it ran perfect ever since! They are pretty cheap and easy to replace. If it is still the original distributor in your truck, this would be my guess.

 

I just purchased a 77 f150 4x4 and it was doing the same thing, start and run for a while then die, and it wouldn't start back up again for a while, then the same thing, except when i would try to start it after it died it would pop and sputter a little like it wanted to go but it usually backed up through the carb and instant dead when you let go of the key.

I ran a hot wire straight from the battery to the coil and it runs great.

I'm going to replace the ignition switch and see if that fixes it but till then probably a toggle so i don't have to keep opening the hood

 

__________________________________________________ ___________

I don't know what to suggest other than what we told "BlackCustom77" and he never did come back to say what he did. Maybe he will see this and come on line.

 

Ditto on the vapor lock. Mine is a 400, but same symptoms. Finally died where I could check a few things. Pulled fuel line to carb and no fuel. Had my wife crank it while I held the fuel line in a water bottle. No fuel. After maybe 30 seconds of trying, fuel started coming out. Hooked line back up and it started fine. I put some insulating aluminum shield between the fuel pump and the exhaust manifold. No more problems so far.

 

Change the Pickup coil out to a Motorcraft. the chinese parts wear out in over a month.

 

On the theory "easy things first" check out your rubber fuel lines. On mine, the old lines were soft when wet and got sucked shut by the fuel pump after soaking for a while. When dry they were hard as a rock. I'd drive 10-20 miles and that was it. I replaced rubber lines and all is well.

Also, there is a fuel filter at the pump. "Number Dummy" has the specifics. Check/change all rubber lines and fuel filters first.

 

i had the same problem about a year ago on my "78" f-150 with 400m 4 speed. it ran great but when i bought it the truck had sat for about 2 years. it would run great then all the sudden it would die and not start. i thought it was a fuel problem to. turns out i was wrong. so i went for spark! there was no spark at the coil wire a new coil, a new module! started right up i was happy as hell about 15 mins went by and it died. the problem was the magnitic pick up inside the distributor. thats what the module is hooked to. i also found it was cheaper to replace the whole distributor than just those little pickups. there is no adjustment on them like the old points but im sure if you check the spark coming from your coil you will find the problem. hope this was helpfull