I'm installing a hypertech inline fuel pump, keeping the stock pump in the tank. The power wire for the pump is running to the starter solenoid, with the ground going to a relay. The relay is spliced into the fuel pump trigger wire (grey wire) over the rear axle.

I keep getting a code 54, low voltage at the fuel pump or fuel pump relay. I've replaced the fuel pump relay and the relay that is wired in at the inline pump. When I turn the
key to ignition on, neither pump energizes like they are supposed to. The only way I can start the car is by cranking it, and then the oil pressure switch activates the fuel pump after about 8-10 seconds. Please help!

 

Odd question, but why didn't you use the existing wires that went to the original pump?

And not that this'll help you diagnose things, but where did you mount that Hypertech pump? If my in-tank pump goes again I'll do the same thing you're doing... replacing the stocker was too much of a PITA.

-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.v6fbody.com mailbags

 

Stock pump is still in the tank and works fine. It is about a year old. I'm having fuel delivery problems, thats why I need the extra pump, and didn't feel like dropping the tank. Using a fuel pressure gauge mounted on the windshield, and pressure at 60 psi, the pressure would drop once I hit around 4500 rpms full throttle. Also, at high pressures, 60-65 psi, the fuel gauge needle would bounce back and forth. This is all before I mounted the in-line pump.

The pump is behind the rear seat to the left of where the stock fuel pressure filter was. I am using a high flow aluminum SX filter. I can drive the car, but only when the oil pressure switch turns on the pumps, and I still get the code 54.

Still need help!

 

I used seperate relay for external, tapped gray wire to stock pump as control signal for relay, other end of relay signal to ground. Then for external pump on same relay tap on to 12v, out to external pump. That way external pump turns on/off with stock pump. Worked for me.

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-Jimmy-
91 Formula 5.7

 

So you only used one relay or two? Did you get a code 54?

I ran my power wire straight to the starter solenoid instead of to a relay. Wouldn't my set-up work, or did I wire something wrong?

 

Still need help.

 

I used only 1 relay for ext pump and got no code, and got 12v for ext pump straight from battery (isnt solenoid energized only when starter keyed on?) and added inline fuse. I did this couple years ago hoping wouldnt need to pull bad pump from tank. The electrical was good but external pump couldnt quite pull and overcome bad stock pump, would hesitate and buck at start of wot, so removed intank and since then using stock relay/wiring to external pump.
If by chance still get 54 then can completely isolate external pump wiring from stock by tapping on a "hot in run" line as relay signal.

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-Jimmy-
91 Formula 5.7