Frustrating Fuel Pump Issues
10-09-2017, 03:00 PM
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Frustrating Fuel Pump Issues I will try to keep this short but I want to provide some background so someone can possibly help me.
Car is a 1999 LS1 Camaro. It sat in storage for a few years where it rarely got driven or even started. 4 years ago I finally had a place to keep it in a garage at home so I brought it home so I could drive it on weekends or nice days. Since I brought it home, the gas gauge didn't work which I assumed mice got into wiring because when I turned the heat or a/c on, I could smell mouse pee coming out of the vents. It didn't bother me that much as I would just fill it up and reset the trip odometer each time.
A couple of weeks ago, I tried to start the car and it wouldn't start. I ended up putting a fuel pressure gauge on it and saw I had no fuel pressure. During my initial diagnostics I changed the fuel filter. I thought maybe a relay was bad so I took the fuel pump relay out and used a wire to jump across two terminals. I believe it was 30 and 87. This did seem to work as I could hear the fuel pump run and I had pressure. I put the relay back in and the car started without any problems. Later that week, the same thing happened and jumping the relay didn't help. I decided to cut a trap door in the trunk area to get to the fuel pump. Most of the wiring was chewed through a few inches down from the connectors. It seemed like mice had eaten everything except the power wires for the fuel pump. They ate through the plastic look wherever they had eaten the wiring. I intended to disconnect the wiring under the rear axle and take the whole harness out but the tank was full of gas, I was afraid I wouldnt be able to get the harness back in without dropping the tank, and it looked like I could easily access the bad sections of wire. I cut out the chewed sections, soldered and heat shrinked new sections in, plugged it all back together and it started right up. I put a door on and put the car back together.
The next day, I drove the car 4-5 different places and shut it off at each stop, came back out and started it up to drive to the next place. No issues the whole day. Next morning I go out to my garage to start it up and have the same issue. At this point I'm thinking I have a bad fuel pump that is only working half the time.
I went ahead and ordered a new Racetronix fuel pump. Talked with Texas Speed and they assured me that if the car was stock, I could get by without the heavy duty wiring harness. Installed the new pump, and before I reinstalled the trap door and carpet, I started it and shut it off twice with no issues. Put everything back together and the next time I tried to start it, it wouldn't start and I couldn't hear the fuel pump priming when I turned the key on. I tried multiple on/off cycles with no luck. Yesterday I again pulled the relay and tried jumping a wire to bypass it and pump would not prime. I left the wire in place of the relay and pounded on my trap door plate with my fist and heard the pump kick on. I put the replay back in and it started up. I let it run for 10 minutes with no issues and this is as far as I have gone.
Normally I would think maybe a broken or loose wire, but once the car starts it doesn't die. I drove it probably 70 miles in one day without any issues. I would think if it was a loose connection of some sort I would have had issues along that way.
The only possible thing I can think of at this time, is that there must be a different wire that sends power to the pump to prime it vs what powers it when the car is running. Is that the case? If so, can anyone tell me which wire is what?
Car is a 1999 LS1 Camaro. It sat in storage for a few years where it rarely got driven or even started. 4 years ago I finally had a place to keep it in a garage at home so I brought it home so I could drive it on weekends or nice days. Since I brought it home, the gas gauge didn't work which I assumed mice got into wiring because when I turned the heat or a/c on, I could smell mouse pee coming out of the vents. It didn't bother me that much as I would just fill it up and reset the trip odometer each time.
A couple of weeks ago, I tried to start the car and it wouldn't start. I ended up putting a fuel pressure gauge on it and saw I had no fuel pressure. During my initial diagnostics I changed the fuel filter. I thought maybe a relay was bad so I took the fuel pump relay out and used a wire to jump across two terminals. I believe it was 30 and 87. This did seem to work as I could hear the fuel pump run and I had pressure. I put the relay back in and the car started without any problems. Later that week, the same thing happened and jumping the relay didn't help. I decided to cut a trap door in the trunk area to get to the fuel pump. Most of the wiring was chewed through a few inches down from the connectors. It seemed like mice had eaten everything except the power wires for the fuel pump. They ate through the plastic look wherever they had eaten the wiring. I intended to disconnect the wiring under the rear axle and take the whole harness out but the tank was full of gas, I was afraid I wouldnt be able to get the harness back in without dropping the tank, and it looked like I could easily access the bad sections of wire. I cut out the chewed sections, soldered and heat shrinked new sections in, plugged it all back together and it started right up. I put a door on and put the car back together.
The next day, I drove the car 4-5 different places and shut it off at each stop, came back out and started it up to drive to the next place. No issues the whole day. Next morning I go out to my garage to start it up and have the same issue. At this point I'm thinking I have a bad fuel pump that is only working half the time.
I went ahead and ordered a new Racetronix fuel pump. Talked with Texas Speed and they assured me that if the car was stock, I could get by without the heavy duty wiring harness. Installed the new pump, and before I reinstalled the trap door and carpet, I started it and shut it off twice with no issues. Put everything back together and the next time I tried to start it, it wouldn't start and I couldn't hear the fuel pump priming when I turned the key on. I tried multiple on/off cycles with no luck. Yesterday I again pulled the relay and tried jumping a wire to bypass it and pump would not prime. I left the wire in place of the relay and pounded on my trap door plate with my fist and heard the pump kick on. I put the replay back in and it started up. I let it run for 10 minutes with no issues and this is as far as I have gone.
Normally I would think maybe a broken or loose wire, but once the car starts it doesn't die. I drove it probably 70 miles in one day without any issues. I would think if it was a loose connection of some sort I would have had issues along that way.
The only possible thing I can think of at this time, is that there must be a different wire that sends power to the pump to prime it vs what powers it when the car is running. Is that the case? If so, can anyone tell me which wire is what?
10-11-2017, 09:45 AM
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No, the priming is done by either the BCM or PCM. If you notice, on first key turn the pump will prime and then shut off. This is intentional, and it will not turn back on again until the motor is seeing rpm. It is all done through the same wiring. At this point, since youve seem to address the wiring issues i would check for pressure bleed off. Are the rails holding pressure after the prime cycle is over?