Help! Our 1979 Ford F150, 4x4, with a 400 in it will not stay running. We can drive about 5 miles, then it quits, wait about 15 minutes and continue on. We have replaced the ignition coil, ignition module, pickup coil, fuel pump, lines, filter, and even pulled the tank to clean the screen. If anyone has a solution, we would greatly appreciate it.

 

You need to find out if it's a electrical or a fuel problem. The next time it quits pull a plug wire & check for spark. Check carb for fuel.

 

Is it dying every five miles or just once after the initial start up?

 

I am going to guess you have a fuel problem. Your pump is weak so it has just enough to get some fuel to the bowls at idel, but when you need more like when driving, it cannot keep up with fuel demand. Check to make sure all your passageways are clear and free flowing. Also, do you have a corroded tank? I had one and I let it run dry so it picked up all that junk and toasted the fuel pump. Maybe it is time for a carb rebuild also. Give it a try!

 

T,
It's possible you are running too rich.
If the choke is stuck shut, you could be flooding out.
Once the vehicle is warmed up, it requires a leaner mixture.
Does the motor just stall quickly, or does it stutter out and not restart?
Secondly, vacuum leak? Could this be a possibility? EGR valve could be sticking open?
Give us some more clues, I'll go form there.
KingFisher

 

i had the same problem, try installing a straight line instead of the fuel filter, my gas tank has a bunch of crap sittin in it so when i did that it was fine

 

Here's a few more guesses:

1. Carb fuel filter - in carb body where fuel line enters?
2. Carb bowl float?
3. Replace EGR valve?

Good Luck!!

 

When does this happen? Is it usually hot when this happens? Might be some vapor locking in your fuel lines/ filter. make sure all fuel line is a good distance from hedders, manifolds, exhaust pipes, block, etc. Im having vapor locking on ocassion now, and before next summer im going to have to re route my fuel lines. Also if you have an electric fuel pump, mounted on a frame rail, that might be getting hot too.


---JOHN

 

From what you described, it sounds like a fuel delivery problem. The best way to prove this--The next time it stalls, remove the air cleaner and look down the carb while actuating the throttle. If you don’t see the gas spray into the carb, it is most likely a fuel delivery problem. You can verify this by removing the screws in the top of the carb, be careful not to drop any down the carb, and see if there is any gas in the fuel bowl. If not, it is definitely a fuel delivery problem.

If you do see the gas spray into the carb, it’s mostly likely an ignition problem. This can be confirmed by purchasing an ignition tester at your nearest Autozone or Advanced Auto store. They usually look like a spark plug with a grounding clip welded to it, or a neon light that mounts between the sparkplug and the sparkplug wire.

Clogged fuel lines, or a bad fuel pump usually causes fuel delivery problems. Of the two, the clogged line is most common; typically, it’s the screen in the tank. Since you have removed the tank and checked it and the screen for cleanliness, you may wish to try this: Remove the fuel hose going to the carb, and install a pressure gage, then have someone crank the engine, while you read the fuel pressure. Next, use compressed air to blow out the lines going back to the tank. Crank again, it the pressure increases, you most likely found and fixed the problem. If not, then replace the fuel pump.

Please write back and let us know what you find.
John24255