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05 Pontiac Grand Prix 3.8 N/A
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6 Posts
Discussion Starter · #1 ·
Ok, so my GTP has been having issues from one end to the next... Replaced Gummed up injectors, TPS, IAC, Fuel Pump 2 speed relay, and supposedly the guy that owned the car before me (who told me he bought and sold cars after he fixed them... But had apparently given up on this one...) said he installed a new fuel pump. Fuel pressure tested at 42 lbs. Then got worse quick. But I checked voltage and it's only getting 2.5v to the pump. Even after turning the car over... Now, I know there is a fuel pump control module somewhere... But I was curious if anyone knows how to test the module? What voltages does it apply at idle and under boost? Now... I did take a battery and hooked 12v directly to the pump and it was still low psi! So I have got a new one... But that doesn't fix the voltage being low to the pump! Where if any... Are there any grounding problem areas for the pump I should check?馃 Is there another sensor that controls the fuel pump control module? And where is the module located? I've looked online with no luck finding it where I would think it is located from looking online. Any info to point me in he right direction is appreciated!
 

Registered
05 Pontiac Grand Prix 3.8 N/A
Joined
6 Posts
Discussion Starter · #2 ·
Ok, so my GTP has been having issues from one end to the next... Replaced Gummed up injectors, TPS, IAC, Fuel Pump 2 speed relay, and supposedly the guy that owned the car before me (who told me he bought and sold cars after he fixed them... But had apparently given up on this one...) said he installed a new fuel pump. Fuel pressure tested at 42 lbs. Then got worse quick. But I checked voltage and it's only getting 2.5v to the pump. Even after turning the car over... Now, I know there is a fuel pump control module somewhere... But I was curious if anyone knows how to test the module? What voltages does it apply at idle and under boost? Now... I did take a battery and hooked 12v directly to the pump and it was still low psi! So I have got a new one... But that doesn't fix the voltage being low to the pump! Where if any... Are there any grounding problem areas for the pump I should check?馃 Is there another sensor that controls the fuel pump control module? And where is the module located? I've looked online with no luck finding it where I would think it is located from looking online. Any info to point me in he right direction is appreciated!
It's a 97!
 

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885 Posts
A) do the speed control delete... Most vehicles run pumps at full voltage full-time, and it's only been an issue for L67 folks who eventually had a failure of the speed control system (resistor, etc.). I'll look for the details on this, some archives online may still have the details (bending a relay pin, and/or jumpering the resistor wire to avoid using it). I've got this done on my '04 Regal, and did it on my '98 GTP, too.


B) I highly suggest getting a relay'd fuel pump rewire from ZZP, Racetronix, or wherever, so the pump has a cleaner and larger power wire, with a fresh ground you have eyes on during install. This eliminates that concern, so you're just dealing with the pump and other components as your issue, if it remains. (I've had both companies' re-wire setups, and each does the job well, although the Rx one via PRJ is no longer on the market.)


Salem makes some videos tinkering, and is easy for me to reference. He doesn't get everything 100% right, but for the sake of the overall topic, he does well.
 

Super Moderator
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885 Posts
Well, it's eliminating the use of speed control, so now you'll want to ensure the wiring to the pump is good.

ZZP's is pretty bare bones, but does the job for $35 (had this on my GTP). And they have basic install instructions linked.
Font Auto part Electric blue Circle Gadget



Racetronix is a bit fancier, but you get what you pay for, if you're into that for $69 (have this on my Regal).
Tints and shades Auto part Font Circle Eye glass accessory
 

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05 Pontiac Grand Prix 3.8 N/A
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6 Posts
Discussion Starter · #6 ·
Being as I'm in college.... Cheaper is better... But I've got an old wiring harness and the pin disconnectors that I can make one myself probably. Thanks! Also... When you bend the leg of the relay that bypasses the fuel pump control module? Thanks again
 

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Yes, it doesn't allow the relay to trigger & re-route FP power through the resistor and slowing the pump, so it stays at normal high speed, like any other car.

The main reason you'll need to buy something is for the thicker gauge wire, which is the point of it. Based on the simplicity of ZZP's (which I also bought in my budget-minded college years), you can either 1) run a ~10-14ga wire from their connection point behind the relay panel, back to the FP connector & build a go-between harness from 2 spare connectors, or 2) similar to RX's, run thicker power wire from a front alternator/battery/fuse box stud, and have the factory harness power signal trigger a relay in the back via a go-between harness (their CTS-V version is more like the one I bought, not sure why their W-body one is funky at the FP connector now).

For either one, you'll also want to have a ground wire that mounts to the trunk area cleanly to replace the long, thin wire in the factory harness. It's certainly do-able, so just brush up on everything you'll be doing, and mark your wires with masking tape to keep track, if it helps.
 
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