I have a f-150 1986 straight 6 300 with the 4spd 2wd tranny. So far I've dropped the gas tank, the rear one, it's perfectly clean on the inside, looks like new. Patched the hole in the corner. I've been having issues with getting fuel to the carb it's like it refuses to pump gas, it has a brand new pump I put in today. I took it down the road and got it up to 57mph, that's the fastest as I've ever had it before it would cut out at 45 or so due to lack of starvation of fuel. I'd pop the hood nothing in the filter, crack the line and there's pressure, lots of air, then it will pump more gas. When I got the truck when it was running the filter was all the way full of fuel, now it's half at best. But I go down the road and get back it's empty, WTH? any help would be gladly accepted. Also I put 5 gallons of gas in it. Another thing, it didn't do this when I bought it, it started this after I had the head shaved due to being warped. Has a newer fuel filter.

Thanks ~Andy

 

Is your switching valve for the tanks still hooked up? If it is, bypass it and run on one tank and see how it does.

 

If you have pressure it seems like the pump is working but getting air somehow. Maybe the pickup in the tank isn't at the bottom? I'd try adding fuel, and see if it then gets a good fuel supply.

The '81 F150 I got in October starves for fuel if the tank is less than 1/2 full. Haven't diagnosed the problem yet but I suspect a problem with the fuel pickup in the tank.

 

Hey, it's fixed now. You were both right, I was getting air into the line, it was the switch, I didn't bypass the switch, but I took a vac. Plug off my intake manifold and put it on the plug for the front tank to plug it, and now the filter is full and the 300 is a happy camper. Thanks again guys(or gals) I've been fighting this for a month or so I guess I shoulda just came on here and made a thread but I was too lazy.