fuel pump on 390
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New User
Joined: Oct 2012
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From: Austin
fuel pump on 390
Sorry for the duplicate post gents, I am new here and just noticed if you scrolled down there where engine specific forums!
I am the proud owner of a '73 with a 390 that will not start...
When I spray a bit of quick start in the carb she fires right up, but then quickly dies off. Took off the fuel filter (which looks to be relatively new) and floored it, tried to crank it..... and nothing. No gas out of the hose.
I did also noticed that the last time I drove it under any acceleration past 1/4 throttle i got no elevated response. She even stalled out a bit under heavy throttle.
Three questions.
1. Do you guys think it is most likely the fuel pump?
2. Is there anything else I need to test before trying to replace it?
3. How hard is a fuel pump for a novice to try and replace? (aka, should I get a mobile mechanic)
I am the proud owner of a '73 with a 390 that will not start...
When I spray a bit of quick start in the carb she fires right up, but then quickly dies off. Took off the fuel filter (which looks to be relatively new) and floored it, tried to crank it..... and nothing. No gas out of the hose.
I did also noticed that the last time I drove it under any acceleration past 1/4 throttle i got no elevated response. She even stalled out a bit under heavy throttle.
Three questions.
1. Do you guys think it is most likely the fuel pump?
2. Is there anything else I need to test before trying to replace it?
3. How hard is a fuel pump for a novice to try and replace? (aka, should I get a mobile mechanic)
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Audion, when you squirt fuel into the carb & it fires, is the give away. There is no fuel getting to the carb.
You can have a blocked fuel line, a dead pump or blockage in the carb. The only way that I know how to trouble shoot this is start at the top and work back to the tank. Remove the line near the carb, place it in a small mouth bottle like a water or pop bottle have a bud crank it over to see if gas is being pumped. I would next pull the line from the tank at the pump to see if gas is flowing from the tank. You will need a pencil or something to plug the line while it is separated to stop the gas flow if it is working properly.
Another thing pull the oil dip stick and sniff it to see if it smells like gas is in the oil. The pump diaphragm may have ruptured and an oil change will be in order also.
John
You can have a blocked fuel line, a dead pump or blockage in the carb. The only way that I know how to trouble shoot this is start at the top and work back to the tank. Remove the line near the carb, place it in a small mouth bottle like a water or pop bottle have a bud crank it over to see if gas is being pumped. I would next pull the line from the tank at the pump to see if gas is flowing from the tank. You will need a pencil or something to plug the line while it is separated to stop the gas flow if it is working properly.
Another thing pull the oil dip stick and sniff it to see if it smells like gas is in the oil. The pump diaphragm may have ruptured and an oil change will be in order also.
John
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New User
Joined: Oct 2012
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From: Austin
had an hour or so before dark and got battery disconnected, checked all the "soft" lines and everything seemed to be in good shape.
disconnected the inlet and indeed had quite a bit of fuel flowing so i plugged it up.
my question now is how in the world do i get at those bolts on the fuel pump!? anyone know the size off the top of your head? it is really tight in there...
any tips or tricks would be much appreciated as i am hoping to get it up and running by the weekend.
disconnected the inlet and indeed had quite a bit of fuel flowing so i plugged it up.
my question now is how in the world do i get at those bolts on the fuel pump!? anyone know the size off the top of your head? it is really tight in there...
any tips or tricks would be much appreciated as i am hoping to get it up and running by the weekend.
Posting Guru
Joined: Dec 2009
Posts: 2,134
Likes: 1
From: Mississippi
I dont remember the bolt size but I think they are 1/2''. There is no majic involved getting to the bolts, its just a PITA, no two ways about it. On a 4x4 with a 360/390, removing the oil filter helps access the pump and bolts. When you go back in with a new pump it may help you to put a socket on the end of the crank bolt and turn the engine over slowly to get the pump eccentric in the correct position, the arm on the pump will fight you.
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