Fuel

[kylec82]

i have a 1981 chevy truck 305 stock fuel system mechanical pump truck will run for a few mins then die when i take the fuel line off there is no fuel in it ?? why wouldnt the line hold pressure

[jefferias]

i have a 1981 chevy truck 305 stock fuel system mechanical pump truck will run for a few mins then die when i take the fuel line off there is no fuel in it ?? why wouldnt the line hold pressure

dont qoute me on this but i seem to believe that the pump has to be running for there to be any fuel pressure.

[mcreyaufmiller]

The pump only works when the motor is running. if the lines are bleeding back to the tank, you may have a hole in the diaphram in the pump allowing the fuel to run back to the tank.

[Cerberus]

Or you have a bad check valve in the pump. You can d/c the fuel line at the carb and crank it it if you get fuel then the pump is probably working. Another problem you could have is a leak in the fuel hose on the inlet/supply side. Mechanical pumps draw fuel from the tank by vacuum, if there are any leaks in the lines then it would suck air and not fuel. You may not even have a liquid fuel leak on the supply side too.

[BAD2500HD]

i have a 1981 chevy truck 305 stock fuel system mechanical pump truck will run for a few mins then die when i take the fuel line off there is no fuel in it ?? why wouldnt the line hold pressure

I was just wondering if you found what was wrong with your truck ? i have somewhat the same problem but with mine ( it's a 1979 GMC 3/4 T with a 350 ) it runs fine just that after it sits a couple of days theres no gas going into the carb , i have to put a little in the carb to get it started then its fine , one time i was told i had to rebuild the carb i haven't yet but to me it seems like it would be more in the fuel pump or a leak in the line , i have checked the lines and all seem good no leaks that i can see so i am wondering if it isn't the pump , the guy i bought the truck from about 9months ago said that the pump wasn't that old and it had jsut started doing this within the last year. so please let me know what you found out , Thanks 1