I need help! I own a 91' Firebird, after I shut off My engine, about every 45 seconds there is a loud buzzing sound, and then a fissing sound comming from behind the right rear tire, it lasts for about 10 seconds. I think it might be the fuel pump, but not sure. for fear of my car blowing up (since the sound is comming from near the fuel tank) I disconnected the battery. So, anyone have any ideas?

 

sorry, I mean the Left Rear Tire. not the Right!

 

If its what I'm thinking of its the fuel pump.

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Red 1986 SC, 2.8L, rebuilt 700R4, 3.42 Posi, t-tops, 134K miles and counting, K&N air filters, hopefully more to come!

 

could also be the fuel tank, try this: right after you park your bird, turn off the cap of your fuel tank and listen if the noise is still coming. Your fueltank is in a vacuum, and this noise comes from equalizing the pressure in your gastank.
but anyway it shouldn't be that noisy.

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www.marion-becker-nidda.de
91 Firebird 3.1
Modsynomax ultra flow stainless steel

 

So, as long as the battery's connected and the car's off, every 45 seconds you hear the noise? I think you're right; the fuel pump's engaging. You might want to check out the fuel pump relay; it might be getting "stuck" closed.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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the ignition switch kills the FP relay doesnt it?

 

its the fuel pump... it will run so there is enough pressure in the rail for the next start. it normal

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3.8 turbo 20th anniversary transam #497 first owed by Clifford Williams, Bass player from rock band AC/DC

 

Scoob, yup, it "should", but if the relay's stuck...

turbo497, the pump only primes for the next start when you turn the key right before starting the car.

Sometimes the pump will run for 1-2 seconds after the car's shut off. This is due to the "backup" oil pressure swich on the fuel pump circuit. When the oil pressure is high (as in, the engine is running), the switch closes. When the car's turned off, the oil pressure takes a short time to drop to 0 - and this might keep that pressure switch closed enough to run the pump. The pressure switch is identified by the sensor on the oil filter mounting pad that has two wires going to it.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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ermm i mean it totally kills power to the relay and pump.. awhle back my relay died and i couldnt get a replacement right away so i temporarly wired it so it would run all the time by jumpering the two of the haviest wires, bypassing the relay.., once the ignition was cut off so would the pump..

 

I've always known the relay to take it's power directly from the fuel pump/ECM fuse, located on the upper frame rail on the passenger side. That fuel pump/ECM fuse goes right to the positive junction block on the radiator support, which goes directly to the battery (via the starter solenoid).

The relay is controlled by the ECM, but if the relay switch gets stuck, the power feed to the pump will be constantly drawn right off the battery. Your relay went bad in one way (switch stuck "open"); his could go bad in another (stuck "closed"). And I stress "could"- we haven't heard back from him yet & none of us can look at the car. He probably wouldn't have run the test chart if I gave it to him- nobody's run that chart yet; I shouldn't have bothered with it.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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