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Question: Electric fuel pump on stock 81 Vette

FactoryC3

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Joined
Oct 14, 2014
Messages
48
Location
USA
Corvette
1981 Black Coupe Red Interior
Has anyone installed an electric fuel pump to stock fuel
lines under 81 tank? Will the fuel feed strong enough? My feed seems erratic and slow viewing the clear filter before a Holley MitiMite.
think it may be a partial plugged tank sending unit filter/strainer? Filter bowl empties and pressure drops but does come back.
 

Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,388
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
I assume that the pump is mounted lower than the tank. These electric pumps are for pushing fuel and don't like to pull fuel up. They like to be gravity fed. Have you removed the line from the filter inlet to check for fuel flow? That could well be the problem. If there is no flow and your pump is below the tank fuel level, try blowing compressed air back through the line into the tank. Use low pressure around 5 psi so as not to dislodge the strainer if it isn't clogged. Also loosen the fill cap so you don't pressurize the tank. You should hear bubbles coming out in the tank freely.
 

FactoryC3

Well-known member
Joined
Oct 14, 2014
Messages
48
Location
USA
Corvette
1981 Black Coupe Red Interior
Thanks for your reply. The pump is much lower than the tank. When the car is running you can see the fuel filter is only 1/4 full and you can see slow flow entering the filter. When shut off it takes over night to fill back up above the center of the filter. Another thing that is pointing me to a plugged tank strainer is that the fuel pressure drops very slowly when the engine is shut down and the switch is in the on position. I have an in car fuel pressure gauge. I read that the pump will allow back flow when not running.
I am set up to drain the tank tomorrow morning and see what is going on. I will keep thread advised of findings.
 

FactoryC3

Well-known member
Joined
Oct 14, 2014
Messages
48
Location
USA
Corvette
1981 Black Coupe Red Interior
Thanks for your reply. The pump is much lower than the tank. When the car is running you can see the fuel filter is only 1/4 full and you can see slow flow entering the filter. When shut off it takes over night to fill back up above the center of the filter. Another thing that is pointing me to a plugged tank strainer is that the fuel pressure drops very slowly when the engine is shut down and the switch is in the on position. I have an in car fuel pressure gauge. I read that the pump will allow back flow when not running.
I am set up to drain the tank tomorrow morning and see what is going on. I will keep thread advised of findings.
 

SS327

Member
Joined
May 16, 2022
Messages
23
Location
Indiana
Corvette
75 Stingray
Are you having a particular drivability problem or just the level in the filter? Because to me in my experience be it GM or Mopar it sounds pretty normal. If it is just a visual level problem the correct fix would be to buy a filter you can’t see into. Because you are chasing a problem is not there.
If you are having a drivability issue check the basics like fuel pressure, rubber line degradation and fuel pump first. Just some free unsolicited advice. Maybe worth what you paid for it.
 

FactoryC3

Well-known member
Joined
Oct 14, 2014
Messages
48
Location
USA
Corvette
1981 Black Coupe Red Interior
I assume that the pump is mounted lower than the tank. These electric pumps are for pushing fuel and don't like to pull fuel up. They like to be gravity fed. Have you removed the line from the filter inlet to check for fuel flow? That could well be the problem. If there is no flow and your pump is below the tank fuel level, try blowing compressed air back through the line into the tank. Use low pressure around 5 psi so as not to dislodge the strainer if it isn't clogged. Also loosen the fill cap so you don't pressurize the tank. You should hear bubbles coming out in the tank freely.
I just finished the update with my fuel flow. I removed the sending unit/pick up. I did not have to drop the tank but it was tight. I attached photos of the filter sock. You couldn’t see any light through it at all. Thanks for your help. Car run stronger and fuel pressure is stable.
 

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Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,388
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
Glad you have it running right again.

Tom
 

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