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Discussion Starter #41
The car has been running pretty well for the past few weeks. Out of the blue today...fuel pump won't engage. No familiar fuel pump buzz. Could it be bad again already? Any diagnosis tips? Thanks guys.
 

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I'd suspect that the computer is not getting a Hall effect sensor signal, which prevents the fuel pump from running. But don't suspect the Hall effect itself, far more likely that it's a bad connection.
 

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Discussion Starter #43
I'd suspect that the computer is not getting a Hall effect sensor signal, which prevents the fuel pump from running. But don't suspect the Hall effect itself, far more likely that it's a bad connection.
Wouldn't it store a code for the HEP? Nothing but 12 right now.
 

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If you have lost that 'key-on fuel pump buzz', then check for key-on power at the fuel pump.
Has this fuel pump been replaced? I have had cars with multiple fuel pump failures due to water/debris (bad gas) in the fuel tank.
If you have any doubts about how the inside of the tank looks after 28 years, you need to take a look. Bad gas will keep killing fuel pumps.
In worst case scenarios where the inside sheetmetal 'galvanizing' of the tank was falling apart, I have had to replace the tank. If things are rusty back there, disturbing them may cause fuel leaks.
Brake lines and fuel lines are bundled and run together back there.
 

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This sounds very much like an electrical issue to me.

I would check the entire circuit to the pump, it should be energized at 12VDC whenever the pump relay closes. IIRC the pump relay is closed by the ASD relay, so either of these relays could be faulty. You'll need someone to help you cycle the key.

If the circuit checks good, I would probe the pump itself and check that you have a few ohms across the pump terminals. Zero ohms indicates a short, no continuity indicates a break. Both of these conditions are motor failure and require replacement of the pump.

If the pump is mechanically failing, sometimes banging on the tank can jar the blockage loose or move the pump such that it starts running.

Like I said, I doubt this is a problem with the pump itself. It is probably approaching the end of its service life but you have other electromechanical devices (relays) and electrical connections which have been exposed for over 30 years. You're just as likely to see a failure in the wiring as you are the pump.
 
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