Fuel pump question (1 Viewer)

Joined
Jun 21, 2018
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88
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Montana
Hey I need some help! ... Again😕

84 fj60 with mechanical fuel pump. The problem I'm having is that after I drive for about 15 minutes, the truck stalls and there is no fuel in the filter. After several times doing this I've realized that if I disconnect the fuel filter hose, the fuel will refill from the tank to the filter. I can then restart the rig and it runs great for another 15 minutes until it ' runs out of gas' again. It's as if the pump is causing some weird back pressure to prevent suction from the tank. When I open the filter line, then it will work again.
I replaced the fuel pump with one from AutoZone ( I know, but it was easier at the time). It ran great for 60 miles, and now it's starting with the exact same symptoms.
Am I overlooking something?
Or do you think an OEM pump would solve the problem?

The filter is new, the tank is new. The lines are blown out, although I'm still getting a little sediment in the filter from them.

Thanks for any ideas!
7A306264-24A7-430A-9ABD-78BBBA791D8F.jpeg
 
Joined
Jun 21, 2018
Messages
88
Location
Montana
have you tried running with the gas cap removed?
how full is the tank?
Yes. At first I thought it was pressure building up in the tank or something like that. I tried to run without the gas cap. I also tried to running without the lines to the charcoal canister disconnected too. It didn't make a difference though.
 
Joined
Jun 21, 2018
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Montana
Oh.. and it has done the same when the tank was almost empty, but now it's full and still doing the same.

Thanks
 

OSS

Joined
Jun 30, 2017
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Oblivion
Replace the gas cap.
The cap has a one way air bypass valve built into it to allow air in, but no air out. If the tank can't breathe, the vacuum created by sucking out the gas will be stronger than the pump's suction. Also the fuel pump could be tired
 
Joined
Jan 4, 2011
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Vermont
had a Suzuki DRZ 400 on/off road motorcycle. It had a vent line off the top of the gas cap and every once in a while that line would get pinched....usually just after a fill up. Bike would make it about the distance of fuel stored in the carb bowl and then would die. Always a shock but easy fix.

Other thing is your pump just could be junk. I do buy a lot of parts from rock auto but tend to opt for OEM for more important pieces
 
Joined
Jun 21, 2018
Messages
88
Location
Montana
Replace the gas cap.
The cap has a one way air bypass valve built into it to allow air in, but no air out. If the tank can't breathe, the vacuum created by sucking out the gas will be stronger than the pump's suction. Also the fuel pump could be tired
Guess I'll try a new cap and a new OEM pump and see if that does the trick. I'm so close to getting this running reliably, but it seems just out of reach!
 

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