Finished Rebuild - Fuel Pump won't turn on, Power at Ground Pins
05-08-2010, 04:52 PM
#1
Finished Rebuild - Fuel Pump won't turn on, Power at Ground Pins Alright guys... help.
EVERYTHING is together. However, we cannot get the fuel pump to turn on when you turn the ignition on. When we put power directly to the #9 pin (fuel pump relay) on the PCM, the fuel pump turns on and makes noise. Once you plug the drive into the PCM, get in the car, and turn it to on.. there's nothing.
We were poking around with a test light, and some of the pins that are supposed to be grounds, were showing power. Meaning, we had the test light on a ground, and we touched it to a ground pin, and it lit up.
The ground strap on the drivers side is installed, the grounds on the back of the head are tight, the ground terminal on the battery, and the ground on the body right behind the battery. Everything else seems to work, radio, lights, cluster, car cranks (havent been able to crank it much, battery is shot) but the fuel pump just won't make that whine when you turn it to on.
The blue and white cable from the PCM are also connected inside the car like they should be..
My friend just stopped by and we put his 2000 PCM in my '99.. nothing different happened.
Idk what the deal is guys.. anybody?
EVERYTHING is together. However, we cannot get the fuel pump to turn on when you turn the ignition on. When we put power directly to the #9 pin (fuel pump relay) on the PCM, the fuel pump turns on and makes noise. Once you plug the drive into the PCM, get in the car, and turn it to on.. there's nothing.
We were poking around with a test light, and some of the pins that are supposed to be grounds, were showing power. Meaning, we had the test light on a ground, and we touched it to a ground pin, and it lit up.
The ground strap on the drivers side is installed, the grounds on the back of the head are tight, the ground terminal on the battery, and the ground on the body right behind the battery. Everything else seems to work, radio, lights, cluster, car cranks (havent been able to crank it much, battery is shot) but the fuel pump just won't make that whine when you turn it to on.
The blue and white cable from the PCM are also connected inside the car like they should be..
My friend just stopped by and we put his 2000 PCM in my '99.. nothing different happened.
Idk what the deal is guys.. anybody?
05-09-2010, 09:31 AM
#2
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When we put power directly to the #9 pin (fuel pump relay) on the PCM, the fuel pump turns on and makes noise.
Sounds like VATS or the fuel pump relay. Could also be a ground specific to that circuit. Did you install a aftermarket fuel pump kit with additional harness and wiring? If so, you need to check all of that wiring as well. If you have access to a scan tool, turn the ignition ON and command the fuel pump on using the scan tool.
We were poking around with a test light, and some of the pins that are supposed to be grounds, were showing power. Meaning, we had the test light on a ground, and we touched it to a ground pin, and it lit up.
Fuel system circuit problems can be a major PITA to chase. Usually it's something simple, but can takes hours of methodical trouble shooting to pinpoint.
05-09-2010, 03:20 PM
#4
It's hard to diagnose fuel system circuit gremlins online. I'll give it a shot.
Sounds like VATS or the fuel pump relay. Could also be a ground specific to that circuit. Did you install a aftermarket fuel pump kit with additional harness and wiring? If so, you need to check all of that wiring as well. If you have access to a scan tool, turn the ignition ON and command the fuel pump on using the scan tool.
Do you have the factory schematics to verify that? I would also check the body pass through connector located on the driver side floor pan, right in front of the axle. There is a separate harness that connects between the body through connector and the fuel tank/pump itself.
Fuel system circuit problems can be a major PITA to chase. Usually it's something simple, but can takes hours of methodical trouble shooting to pinpoint.
Sounds like VATS or the fuel pump relay. Could also be a ground specific to that circuit. Did you install a aftermarket fuel pump kit with additional harness and wiring? If so, you need to check all of that wiring as well. If you have access to a scan tool, turn the ignition ON and command the fuel pump on using the scan tool.
Do you have the factory schematics to verify that? I would also check the body pass through connector located on the driver side floor pan, right in front of the axle. There is a separate harness that connects between the body through connector and the fuel tank/pump itself.
Fuel system circuit problems can be a major PITA to chase. Usually it's something simple, but can takes hours of methodical trouble shooting to pinpoint.
Could you give me more info on finding the body pass through connector?
I have a factory Pin-Out for the PCM and everything was *** backwards.
Yesterday i accidentally ripped out the fuel pump relay wire from the PCM. My friend wired it back in, and it didn't work. He rewired it again with the original wire, and everything worked. My fuel pump, gas gauge was working, all the lights on my dash were normal. Then, a few hours later after we finished installing everything else in the engine bay, I got in, turned the key, and the fuel pump was dead. Gas gauge was all the way down, just like before.
My friend noticed the ground on the back of the head was broken. Which I think could have happened when I was tucking the PCV hoses behind the head.. maybe I broke it. We crimped a new ring connector onto the wire, grounded it back into the head. Got back in the car, and still nothing. Just like before.
The weird thing is.. when everything was working, the only lights on my cluster were CHECK ENGINE (normal) and a few other lights like my seatbelt and crap. Right now, when everything isn't working, the Check Engine light ISNT on, but the Service Vehicle light is, as well as ABS INOP and a few others that i've never seen before.
I really think I'm going to have to drop the whole motor & tranny back out.
About 12v.. should be enough to function.
05-10-2010, 07:43 PM
#6
Be sure that your OBD2 port has power & ground. Our swap did the same thing (fire the injectors and coils) but no joy. When we corrected our ground problem with the OBD2 port, it fired right up.
05-17-2010, 04:13 PM
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I've played with a similar sounding problem with my uncles 'Vette. If you connect the power wires AT the pump relay, bypassing it, will it kick? If it does, my bet will be VATS. He had a chip made that was set up to override his VATS pin but put it in a different computer (not sure why, but neither here nor there). The short of it, swapped his chip back to the original computer at it fired right up. If your VATS system is screwy it keeps the relay from turning on.
