EFI 434 External Electric Fuel Pump Problem
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Postmaster
Joined: Aug 2001
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From: Delaware
EFI 434 External Electric Fuel Pump Problem
I am running a 434 cubic inch 400 motor, built by Tim Meyer and modified for EFI by me.
This is in my '53 F100. It has a 21 gallon underbed fuel tank, but the tank is mounted under the frame rails and is lower than the external Walbro 255 lph in-line fuel pump.
When the 21 gallon fuel tank gets to 1/2 tank of fuel remaining, the flow to the external pump is reduced and the motor doesn't run properly, and will even shut off.
I have tried to use a 1 gallon surge tank to keep a constant fuel supply, and also a Carter 4594 low pressure pump ahead of the high pressure pump with no improvement. I did this with the knowledge that a low pressure from the pump will lift the fuel the amount necessary to keep the fuel flowing.
Also the underbed tank outlet is behind the rear axle, and the input to the pumps is in front of the axle, so the fuel line snakes up and over the axle between the tank and the pumps.
I am wondering if the line needs to be bled to eliminate any air in order for the pump to lift the fuel.
This is in my '53 F100. It has a 21 gallon underbed fuel tank, but the tank is mounted under the frame rails and is lower than the external Walbro 255 lph in-line fuel pump.
When the 21 gallon fuel tank gets to 1/2 tank of fuel remaining, the flow to the external pump is reduced and the motor doesn't run properly, and will even shut off.
I have tried to use a 1 gallon surge tank to keep a constant fuel supply, and also a Carter 4594 low pressure pump ahead of the high pressure pump with no improvement. I did this with the knowledge that a low pressure from the pump will lift the fuel the amount necessary to keep the fuel flowing.
Also the underbed tank outlet is behind the rear axle, and the input to the pumps is in front of the axle, so the fuel line snakes up and over the axle between the tank and the pumps.
I am wondering if the line needs to be bled to eliminate any air in order for the pump to lift the fuel.
Thread Starter
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Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
I just found out that the low pressure Carter 4594 pump that I installed was backwards. It's amazing that it ran at all. I put it back in correctly. Now I have to see if it's any better.
I have ordered a High Output, High Pressure, in-tank pump and mounting bracket from the people who made the tank. If the truck runs OK with the current setup, I'll wait and install the in-tank pump next winter, because it will be a major project. I have to remove the tank, and cut it open to install baffles. Then get it welded again. The in-tank pump can be installed with just one hole, but it will not really work correctly without baffles.
I have ordered a High Output, High Pressure, in-tank pump and mounting bracket from the people who made the tank. If the truck runs OK with the current setup, I'll wait and install the in-tank pump next winter, because it will be a major project. I have to remove the tank, and cut it open to install baffles. Then get it welded again. The in-tank pump can be installed with just one hole, but it will not really work correctly without baffles.
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