I parked my '88 TA (305 TBI) in the garage, and I heard a whining noise when I got out. I took a minute to track it down, but it was coming from the rear of the car. I took my phone out and reached under the rear bumper as far as I could to make a recording of it. The recording is attached.

I tried to disconnect the fuel pump relay, but I couldn't get the plug off. I was in kind of a hurry, but I didn't want the pump to burn out, so I decided to disconnect the battery. I got about 1/2 a turn on the negative cable when the noise disappeared. I did not lose my radio presets, and the aftermarket alarm did not go off. So I don't think I actually broke the electrical connection.

Am I right in thinking it's the fuel pump relay? The only other thing I can think off is that I recently installed a stainless steel exhaust, and I noticed that the pipe is rubbing on the crossbrace over the axle.

 

Fuel pump relay could be sticking, as could the oil pressure switch.

 

You didn't have the kids in the car did you?

 

I unbolted the fuel pump relay from the car so that I could easily unplug it if the noise ever recurred. Well it finally did, and I pulled the relay. The noise remained unchanged. And while I was under the hood, it seemed like I could hear the noise louder than I would have expected if it was coming from the rear of the car.

8Mike9, u mentioned it could be the oil pressure switch. Where is it located, and how would it make a whining noise?

 

I think 8Mike9 meant that a sticking pressure switch could be leaving the fuel pump on.

My pump can run for some time after the car is shut off. I've stood in the shop a couple of times after parking it, getting out, getting my things from the car, locking it, closing the over head door, locking it, then just waiting, waiting, waiting for the pump to stop running. It always does, eventually.

That's a strange sound for a pump...not a steady pitch or tone....sort of bounces around. I've never heard one sound like that, if it is indeed the pump.

 

Sounds like it might be the "UFO".

A plastic valve thing about 2" dia, about 8" inboard of the driver's side rear wheel. It's a vent valve of some kind.

My car did that too... I would park the car, and especially on a hot day with the tank not very full and a long drive, every few seconds I'd hear something sounded about like something blowing its nose. I fully expected to see a huge loogie laying on my garage floor. Finally one day I parked it and hung around until it started making the noise, and poked around a bit, and that's what it turned out to be. About a $18 part back in the mid 90s. No clue whether it's even still available.

The oil pressure switch in some FI cars (TPI notably) has a set of contacts in parallel with the fuel pump relay. If it sticks on, it could conceivably continue to supply power to the FP even with the key off. (although I think all of that is on the low side of the ignition switch, which would render it impossible, but I don't know and I'm too lazy to look up a schematic and see where it's wired to) I think that's what 8Mike9 is referring to.

 

I NEVER would have thought to check the tank vent. I don't believe they are available new anymore, from what I have read here. But a member did a great photo shoot / write-up on how to rebuild one.

Here it is.

https://www.thirdgen.org/forums/hist...ent-valve.html

Is this the valve you meant?

 

It was a steady pitch. I recorded it on my phone by reaching under the back of the car, so maybe it seems like the pitch was changing becuz I was moving around.

I'll check out that valve... thanx!

 

next time it happens ,take the gas cap off. if it goes away. you have an issue with the tank over pressurizing. im also dealing with this issue ,but in my case the vent line going from the tank to the tank vent control by the charcoal canister is plugged.

 

The oil pressure switch supplies direct battery power to the fuel pump as long as there is oil pressure above 4 PSI, so it might be the oil pressure staying up for a bit.
Or, it could be the switch sticking on for a few moments.

 

.... And the oil pressure switch is screwed into the block, just above the oil filter. Fairly large sender, 3 wire connector. One of the wires runs your oil pressure gague, the other two are the "in wire" and "out wire", providing a secondary power path to the fuel pump in case the relay dies. This is "straight from the battery" voltage, so nothing will stop it if the little switch inside it sticks closed, aside from unplugging that connector. They CAN go bad.

 

I don't know if this is related, but I had an issue w/ that canister last year. I was smelling gas under the hood, and it turned out that the purge valve(?) was stuck and was allowing fuel vapors to leak out. I replaced the valve and the fuel smell went away.

That's also good info about the oil switch sticking and continuing to power the fuel pump. Now all I need to do is wait for the problem to happen again so I can test this stuff...