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Sbc350 fuel pump

e4cutler

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Apr 6, 2015
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Location
Texas
Backstory: During the process of redoing the Jeep. I modified the fuel cell to take an internal stock fuel pump for my sbc350 motor versus an external pump. In addition, the fuel lines have been replaced with braided hose and AN fittings all the way to the throttle body. I put the fuel cell in Friday night and hooked up all the lines. What I thought would happen when I flipped the power switch was the fuel pump would run until the lines were full of fuel thus pushing all the air out and then cut off. What actually happened when I flipped the power switch, was the pump ran for a few seconds then the relay kicked off. I turned power off then on and got the same thing. After 3 rounds of this, fuel came out at the throttle body. Due to a leak at the throttle body, I had to stop and wasn't able to start the motor. Power to the pump goes through the harness/computer and is not direct to the battery.

Question: Is this normal or is something wrong with my fuel pump?

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Since I'm sure it's going to be asked, the reason for only 2 lines is the new cap is vented with a roll over valve built in.


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What kind of fuel injection are you running? Aftermarket fuel injection or is it a GM TBI setup? If it is a GM TBI setup, mine does what you are describing. Turns on for a few second at ignition on. Will cycle off until engine is running and then turn back on to keep system pressure up. I only have personal experience with GM TBI, FAST EZ-EFI, and FiTech. They all do the same thing. Energize at ignition on to pressurize the system, off after a few seconds, then back on at engine start. Not sure what some of the other system do.
 
scooter60 said:
What kind of fuel injection are you running? Aftermarket fuel injection or is it a GM TBI setup? If it is a GM TBI setup, mine does what you are describing. Turns on for a few second at ignition on. Will cycle off until engine is running and then turn back on to keep system pressure up. I only have personal experience with GM TBI, FAST EZ-EFI, and FiTech. They all do the same thing. Energize at ignition on to pressurize the system, off after a few seconds, then back on at engine start. Not sure what some of the other system do.

I assume it's a stock GM tbi. It was on when I bout the Jeep. Says "Rochester Products" on the tbi. Not sure if that helps at all.

But it can't be pressurized if there's air in the lines, correct? That's why I thought it would run continuously until all air was out of the system.


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The computer doesnt know if the fuel system is primed or not, there is no fuel pressure sensor in a factory TBI setup. The computer is programmed to cycle the pump for 3 sec when you turn the key on. The pump only runs when the computer sees signal from the ignition module. What youre describing is exactly how the TBI fuel system is supposed to operate. Also TBI setups are low pressure, theyre only supposed to have 14psi or so fuel preesure.

You do have a return line going from the Throttle body back to the tank still dont you?
 
d_daffron said:
The computer doesnt know if the fuel system is primed or not, there is no fuel pressure sensor in a factory TBI setup. The computer is programmed to cycle the pump for 3 sec when you turn the key on. The pump only runs when the computer sees signal from the ignition module. What youre describing is exactly how the TBI fuel system is supposed to operate. Also TBI setups are low pressure, theyre only supposed to have 14psi or so fuel preesure.

You do have a return line going from the Throttle body back to the tank still dont you?

Yes, that's the second line in the picture. So is there a procedure I need to follow to prime the fuel system?


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Punkin85 said:
Yes, that's the second line in the picture. So is there a procedure I need to follow to prime the fuel system?


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There is no prime procedure especially with an intank pump. If the system has air in the lines, keep cranking the starter till she fires(within reason of course). Like d_dafron said, once the ECM gets a signal that ignition is firing, the pump will turn back on and continue to run. Any air will be pushed past the regulator, thru to return line, and then into the tank.
 
No need to do anything, the first time you fire it up cycle the key a few times like you did and youre good to go. Its not like a diesel, it'll prime itself and fire right up.
 

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