I am a newbie to the board, and I am here to ask for help! I will start by disclosing I am NOT a car mechanic, and I know very little about the history of the pick-up I bought. I will describe the problem as best that I can.

It is 1977 F-150 with a 400 motor and a C-6 auto (owned it for 5 months.) The pick-up fires up and runs great. Ran good all winter. The issue seems to be that when the truck gets hot it gradually starts cutting out and dies. It will not fire back up. If I wait 30 minutes and let everything cool it will fire back up. The second time it happend to me a guy stopped and helped me out. He pulled a plug wire and we checked for spark (there was spark) and then we pulled the fuel line and turned the truck over. No fuel. He thought it was the fuel pump.

My neighbor knows a little about vehicles so here is what we replaced (new fuel filter, a new fuel pump, and a new module for the heck of it.) I took the pick-up for an 8 hour trip with zero problems. I thought the issue was resolved. Today I am pulling a steep grade with a cab-over camper and truck starts cutting out. I pull over before it dies and waited for about 10 minutes and then it fired up and I took off. An hour later, I pull another hill and it cuts out and dies. It took about 45 minutes but it fired back up and got me home.

Any ideas what would cause this? The first 2 times it was in stop and go driving situations and outside temps were in the 90's. This most recent time it was highway driving with a heavy load and temps in the 80's.

It does not appear to be overheating. Engine temps continue to stay in the normal range.

Thanks for any and all help!

 

Vapour lock?

 

Check all your rubber fuel lines to see if they are in good shape, also make sure they aren't routed next to any thing hot like exhaust. My truck had a very similar problem and it was the line coming out of the tank, it was old and cracked and sucking air into the fuel system and seemed to get worse as it go hotter out. It has been fine for over a year now.
-Johnboy

 

That's my first thought, how are your fuel lines routed?

 

Definately vapor lock.

Also when checking fuel lines don't forget the rubber line about half-way on the frame rail.

Josh

 

Thanks for the info! I will be checking fuel lines tonight.

I am not certain how the lines are ran, but I will look over everything and see if there is a potential problem.

Besides lines running next to exhaust.....are there other problem areas I should look for? The pick-up also has dual fuel tanks.

 

I had this problem with my 78, and took me 2 full days to figure it out. In my situation, the lines were ran as much away from anything hot as I could and it would still vapor lock. Finally I was looking at the pump, thinking on how to blow my truck up, and I noticed that the lower rad. hose was touching the pump! So I put an electric pump on it and that solved the problem.

 

I think your first problem was the module. I agree with the vapour lock being the trouble now. Is the cold air boot that goes from the air cleaner to the the lower right side on the rad support still there?? Most here rot off and never get replace. If this is missing then there is no cool air getting to the carb. When I was young and broke I used an aluminium dryer duct to make a new boot and it solved the trouble instantly, on my truck it would only show up when I was pulling our trailer in the heat.