'81 Ford

[Ellis Kinney]

1981 Ford F-100, 300 inch 6 cylinder. Lately it is taking a lot of cranking time to start. It has a new fuel pump and a rebuilt carburetor. Is it possible for a fuel pump to bleed back to the tank? This is the fuel pump that works off the cam lobe and has a diaphragm in it. This only happens if it sits for a couple of days. If I run it every day it starts excellently. Ideas??? Thanks, Ellis

 

[KCTractors]

1981 Ford F-100, 300 inch 6 cylinder. Lately it is taking a lot of cranking time to start. It has a new fuel pump and a rebuilt carburetor. Is it possible for a fuel pump to bleed back to the tank? This is the fuel pump that works off the cam lobe and has a diaphragm in it. This only happens if it sits for a couple of days. If I run it every day it starts excellently. Ideas??? Thanks, Ellis

I had the same problem with my 1984 Dodge D-350 dump truck. I put an electric fuel pump in line. Turn on the ignition for maybe 15-20 seconds and she will fire right up.

 

[37 chief]

1981 Ford F-100, 300 inch 6 cylinder. Lately it is taking a lot of cranking time to start. It has a new fuel pump and a rebuilt carburetor. Is it possible for a fuel pump to bleed back to the tank? This is the fuel pump that works off the cam lobe and has a diaphragm in it. This only happens if it sits for a couple of days. If I run it every day it starts excellently. Ideas??? Thanks, Ellis

The fuel pump will either pump or not. I would remove the air cleaner, make sure the choke is working. and see if the rebuilt carb is pumping a stream of gas for sure, when you accurate the throttle. With gas being pumped in it should start. Stan

 

[JWA]

Sounds like the gas is evaporating from the carburetor bowl while sitting, fuel pump has to refill the bowl. My 65 Mustang which is driven a couple times a month does the same thing, after that first slow start it will almost start before you can take your hand off the key.

 

[mtf]

The fuel pump will leak fuel into the engine.

I have had a time the last 3 years finding a fuel pump that will last for my 64 chvy c60 grain truck. I ordered the 4th one back in March, it was a Carter. So far so good.
The others were a different story, 2 did not last 5 days each, before they
Leaked all the gas from the tank into the oil pan!

 

[Ericp351]

Dead simple set up. Step #1 is to confirm CHOKE and carb. ACC Pump operation.

 

[Fritz Maurer]

If you didn't change the rubber hose between the pump and the frame, do so now.

This was always a failing point across the decades, gas or Diesel.

The hose gets tiny cracks and lets air in, allowing fuel drain-back. Then the pump has to overcome the leak while sucking fuel out of the tank.

Being that old, also possible steel portion of the line is rusted through.

If any of these conditions exist, blowing compressed air into the tank will pin point the leak where gasoline drips out.