Wiring an under-hood fuel pump
#1
Burning Brakes
Thread Starter
Wiring an under-hood fuel pump
If I were to stop using my in-tank electric FP and switch to one mounted under the hood, how would I go about that? Can I operate an underhood FP with the existing relay? Anyone done this? Also, can I pull fuel through my in-tank pump or do I have to remove it and install a straight-through tube in place of it?
#3
Burning Brakes
Thread Starter
Scratch the under-hood part. The pump I was loking at, a Holley, is supposed to be mounted at the bottom of the tank. The wiring is still in question, however. The stock relay energizes for the "priming" phase and then shuts off until it receives a signal that the engine si running (oil pressure???). I want to wire in an external pump that runs when the key is on and stops when the key is off. Do I need to use a completely separate circuit with it's own relay? How would I then disable the stock circuit?
If you are wondering why I'm doing this, the car's return line was crushed by a previous owner at the jacking point. I temporarily repaired it, but it's a constant source of worry for leaks. Since the car is carbed now I don't need a return line if I use a lower-pressure extrenal pump.
And, can I in fact pull fuel through the stock pump while it's not running?
If you are wondering why I'm doing this, the car's return line was crushed by a previous owner at the jacking point. I temporarily repaired it, but it's a constant source of worry for leaks. Since the car is carbed now I don't need a return line if I use a lower-pressure extrenal pump.
And, can I in fact pull fuel through the stock pump while it's not running?
#4
Instructor
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I'm running an 84 corvette with stock pump (in tank) thru an adjustable FPR hooked up to a demon 650 double pumper. I used an automotive relay hooked up to the 4psi oil switch to turn on the pump. No problems starting her up or running her.
#5
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Originally Posted by JLeatherman
The stock relay energizes for the "priming" phase and then shuts off until it receives a signal that the engine si running (oil pressure???).
Originally Posted by JLeatherman
I want to wire in an external pump that runs when the key is on and stops when the key is off. Do I need to use a completely separate circuit with it's own relay? How would I then disable the stock circuit?
Originally Posted by JLeatherman
If you are wondering why I'm doing this, the car's return line was crushed by a previous owner at the jacking point. I temporarily repaired it, but it's a constant source of worry for leaks. Since the car is carbed now I don't need a return line if I use a lower-pressure extrenal pump.
And, can I in fact pull fuel through the stock pump while it's not running?
And, can I in fact pull fuel through the stock pump while it's not running?
I have never tried to pull fuel (electric fuel pumps are better pushers than pullers) through a dead electric fuel pump, but I can't imagine it not being a significant impediment to free flow.
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#6
Burning Brakes
Thread Starter
A pump directly wired to the ignition switch would actually run slightly more than the stock set up. I don't understand how that will alleviate the need for a fuel return line.
The amount of fuel pressure is not the reason for the return line. The low pressure used by a carb isn't all that much lower than the spec for TBI. Your time and efforts may be better spent doing a proper repair on that return line rather than trying to reinvent the wheel, to eliminate it. Also, the pressures in the return line are minimal.
The amount of fuel pressure is not the reason for the return line. The low pressure used by a carb isn't all that much lower than the spec for TBI. Your time and efforts may be better spent doing a proper repair on that return line rather than trying to reinvent the wheel, to eliminate it. Also, the pressures in the return line are minimal.
http://www.jegs.com/webapp/wcs/store...48050_-1_10307
It's internally regulated and does not use a return line. Same as this one:
http://www.jegs.com/webapp/wcs/store...47713_-1_10307
#7
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To me it seems a shame to discard a perfectly good pump that will develop two or more (ten?) times the pressure for a low performance pump such as that, just to save doing a proper fix on the return line. Besides the $73.00 plus $10.00 - $12.00 handling, you still have to mount it, wire it, and plumb it. It seems to me you already have a better pump, in the ideal location, all wired and plumbed, save one crushed section of steel line. Its your car, your time, and your money. Have fun.
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#9
Melting Slicks
To me it seems a shame to discard a perfectly good pump that will develop two or more (ten?) times the pressure for a low performance pump such as that, just to save doing a proper fix on the return line. Besides the $73.00 plus $10.00 - $12.00 handling, you still have to mount it, wire it, and plumb it. It seems to me you already have a better pump, in the ideal location, all wired and plumbed, save one crushed section of steel line. Its your car, your time, and your money. Have fun.
RACE ON!!!
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My carbed '85 project car has a TBI pump in place of the TPI pump, with a Mallory return style regulator (attached to the original OEM lines, utilizing the OEM fuel filter).
#10
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Originally Posted by JLeatherman
I'm intrigued by the 4psi switch/oil relay wiring. Anyone know how this is done? It would eliminate the priming/stopping part of the startup.
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