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After a 350 mile trip, my fuel pump was making a loud noise.. It sounded like an air raid siren!
The noise was coming from behind the driver-side rear wheel.
I also smelled gas, so I suspected the pump was done (100K miles), although it never quit pumping.
But after installation of a new pump assembly, I still have a noise. Not as loud as before, but the noise:
- Pulses with the turn signal (indicating it's electrical)
- Occurs for 4 seconds when you turn the key to 'on' but don't start (again, electrical)
- Takes some time after startup to occur.. As much as 30 minutes.
- Opening the gas cap has no effect on the noise.. It's not pressure (or vacuum) in the tank
I know the system to pull fuel and equalize the 2 tanks is complicated..
Could anything else explain this noise? Or do I have a bad fuel pump out of the box?
I'm posting what I found.. This MIGHT explain some of the problems people have been having with noisy fuel pumps.
I inspected the ground point described by user "C5 Diag" in the post I reference above. Here is the location with the driver side rear wheel removed:
Ground point circled in red
After removing the nut, it appears that the ground point was mostly painted over with chassis paint! I've owned my car since 1999, so this is all untouched by anyone since the factory.
I used a Dremel tool to grind away the paint and expose bare metal:
I will need to put some miles on this before I can call it FIXED... I will post back to this thread in a few weeks.
This is where doing simple tests yields quick wins. Had you measured the resistance and load tested the ground, you would know for certain if the ground connection was insufficient(despite is outward appearance), and if your dremel efforts provided any benefit.........without even driving the car.
We haven't had any hot days yet.. so I can't say if this problem is fixed. I did decide to change the fuel filter.. I cut the old one open.. It looks a little gritty.. Possibly clogged?
May have got a dirty tank of gas. I will post back here if anything else of note is learned.
I'm having what may be the same issue in my '99 and wondering if I can join this conversation to troubleshoot a resolution.
Noisy fuel pump; fluctuates with blinkers, brake lights, or power windows; can hear with ingnition on and engine off, as well as with engine running; gets louder with heat; didn't have this noise beginning of last fall, but started end of fall.
Cleaned all grounds except the one I couldn't find at the back of the engine. Cleaned all splice packs near the grounds, and the one behind the tail light, and the one under the battery tray.
Replaced the fuel pump and filter, and it seems worse.
Fuel pressure is 55-60 psi hot/cold/noisy/quiet/ignition on/engine running
My skill level with electrical and reading wire diagrams is poor. I've turned more than half the bolts on my car (not counting the tunnel plate) but I'm lost with electric so please bear with me...
When I check the ground with the four prongs of the wire going to the fuel pump, they were 0.0, 0.65, 0.0, 1.0. This was done direct from the battery and again at the ground behind the driver rear wheel.
When I checked the voltage between any combination of the four prongs on the wire going to the fuel pump, it read 4.8V between prongs 2 and 3, 4.8v between prongs 3 and 4, and 0 every other combination. The battery was 12.0v at the time.
I think my battery may be going low (it's an optima red top from 11/24 that was taken out of the car all winter) but didn't know if that should contribute to the noise when the car is running over 13v.
If this is unrealted to the OP, I'll move out of this tread.
Thanks in advance, this sound is annoying when hot.
I'm having what may be the same issue in my '99 and wondering if I can join this conversation to troubleshoot a resolution.
Noisy fuel pump; fluctuates with blinkers, brake lights, or power windows; can hear with ingnition on and engine off, as well as with engine running; gets louder with heat; didn't have this noise beginning of last fall, but started end of fall.
Cleaned all grounds except the one I couldn't find at the back of the engine. Cleaned all splice packs near the grounds, and the one behind the tail light, and the one under the battery tray.
Replaced the fuel pump and filter, and it seems worse.
Fuel pressure is 55-60 psi hot/cold/noisy/quiet/ignition on/engine running
My skill level with electrical and reading wire diagrams is poor. I've turned more than half the bolts on my car (not counting the tunnel plate) but I'm lost with electric so please bear with me...
When I check the ground with the four prongs of the wire going to the fuel pump, they were 0.0, 0.65, 0.0, 1.0. This was done direct from the battery and again at the ground behind the driver rear wheel.
When I checked the voltage between any combination of the four prongs on the wire going to the fuel pump, it read 4.8V between prongs 2 and 3, 4.8v between prongs 3 and 4, and 0 every other combination. The battery was 12.0v at the time.
I think my battery may be going low (it's an optima red top from 11/24 that was taken out of the car all winter) but didn't know if that should contribute to the noise when the car is running over 13v.
If this is unrealted to the OP, I'll move out of this tread.
Thanks in advance, this sound is annoying when hot.
I have no idea what kind of testing you are trying to accomplish here testing "combinations of 4 prongs" of your fuel pump circuit but with your admitted lack of electrical skills it is best to take your car to an automotive electrical repair shop in your area...you should be doing voltage drop testing of your fuel pump circuit if anything...there are many good YouTube videos on basic electrical theory and testing.
Thanks for the replies. I'll stay out of this tread with any further questions. Just seeing the term "voltage drop test" was helpful.
Just remember we don't do open circuit voltage testing (OCV) at the pump like checking for 12 volts at the connector...this measurement is meaningless...we also don't use resistance checking either...the circuit must be tested dynamically...current must be flowing !!
I have a similar problem in my 1997 C5. The noise occurs mostly on hot days, after driving 25 to 30 miles and mine also changes tones to the pulses of the turn signal. I am on my fifth fuel pump so I would agree with you in that the issue suggests electrical issue and not a fuel pump issue. The issue manifests itself as a symptom of noise in the fuel pump but it is not a pump issue. It is something else. I have been chasing this for a couple of years now. Along with five fuel pumps, I have replaced the evap cannister purge valve, the fuel pressure regulator, the jet pump in the right side fuel tank, the fuel pump fuse and relay and cleaned every ground on the car. Nothing has helped. The fuel pump still whines like a banshee in hot weather after a long drive. So Fred, if you discover what is cause the noise in your fuel pump, I would greatly appreciate a holler to let me know what you found. Thanks - Tom
C5 DIAG: You are describing my fuel pump issue on my 97 C5. Same thing. Gets hot and starts to whine and fluctuates with the blinkers, brake lights, etc. If you discover what is causing it, I would be very beholding to you if you would pass on the information. I have been chasing this issue for a couple of years now and it is so annoying that I don't drive the car in hot weather for that reason.
C5 DIAG: You are describing my fuel pump issue on my 97 C5. Same thing. Gets hot and starts to whine and fluctuates with the blinkers, brake lights, etc. If you discover what is causing it, I would be very beholding to you if you would pass on the information. I have been chasing this issue for a couple of years now and it is so annoying that I don't drive the car in hot weather for that reason.
If you see fluctuating lights may be on the ground side..I'd do a voltage drop check on the pump circuit !!
I put a new fuel filter in mine too but the noise still starts after driving for a while in hot weather. It's definitely not the pump as I am on my fifth pump and they all make the same noise. Please let the forum know if you find the problem. I have been dealing with my fuel pump noise issue for two years and as I said, I have gone thru five pumps. It's not a pump issue. Something is causing the pump to make noise but what? That is the question.
Fuel pump noise - but not the pump!
