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BAD FUEL PUMP?????

Old Jun 26, 2010 | 06:29 PM
  #1  
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BAD FUEL PUMP?????

Hello all, here's the breakdown; 89 rs 305 tbi stalls on occasion when idling since i have owned her(she starts right back up after), gas tank leaks if i fill her past 3/4 tank.

A few days ago i pulled in to a buddies place for a few minutes, got back in and she wouldn't start. shell turn but wont run. noticed brown prestone, figured head gasket causing bad ignition or something around those lines so i popped off the air cleaner to see if she was getting any gas just to make sure. gas appeared to be getting in there which reinforced my ignition problem theory. BUT....if we would pump the gas first a few time...she'd start up for a split second then die.

So i got a tow home and started pulling plugs, they all sparked when i tested them and all looked oil free, so i popped off air cleaner for a second time. This time No gas at all and if i pump if first nothing changes.
So my theory quickly changed from Ignition problem to fuel pump/fuel system related problem. fuel filter was changed about 2 months ago. Ive been reading about ways to test it..... terminal g......just listening... didn't have any wire around so i got someone to turn it to run possition while i listened at the tank for the pump to prime. No noise at all in there.

My guess is its the fuel pump that's finished, figured maybe since its leaking when full, there's a hole somewhere so maybe some corroded metal or dirt got in there and clogged it.

Any ideas are welcome. Ive been reading about relays but my electric skills aren't very good so i need a more thorough breakdown of how to do these tests and were to start.
Thanks in advance
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Old Jun 26, 2010 | 09:16 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

Driver side firewall, between brake booster and fender, there's a bracket held to the firewall with 2 10mm screws - on the innerside of that bracket are 2 relays, one has large black wire with red stripe - that one is fan relay, the other is fuel pump. You can test by swapping the two if they are the same stlye - just get a sharpy and mark the fan relay "fan" and mark the other "fp" first, then you'll know later which one is the bad one. If you swap and the pump primes, then you know it was relay - replace it for $8. If not, then either your fan relay is bad too, or the pump is dead.

On a TBI car you won't see the injectors squirting fuel unless the key is on.
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Old Jun 27, 2010 | 10:14 AM
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Re: BAD FUEL PUMP?????

Thanks for details, and by the way i was cranking it when checking for fuel
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Old Jun 27, 2010 | 05:30 PM
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Re: BAD FUEL PUMP?????

So i found the big black red stripe wire, there was four wire going in that circuit, the other big one was red, i switched the black/red with the red and listened while turning the key. nothing once again. don't know if what i did was correct way, if it is; does this mean a bad fuel pump? where are the grounds that i can check? is there a way just to bypass the relay?
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Old Jun 27, 2010 | 05:41 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

Assuming your cooling fan worked, then by swapping the relays and putting the good cooling fan relay in place of the fp relay would have solved the issue if the relay was bad, but didn't change anything, so it's not the relay.

Did you look at the relay wires and connections in the relay socket when switching? Does it look like it's shorted anywhere (burn marks)?
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Old Jun 27, 2010 | 06:02 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

I'm sorry - been racking my brain and having a hard time remembering the colors of the wires on the fuel pump relay. You can take the relay off the connector, and jump two of the pins, but which 2 pins I forget. Think maybe the gray to the orange? Check with a volt meter - see which pin has 12v, try jumping it to each of the others EXCEPT the black, and see if the pump runs.
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Old Jun 28, 2010 | 04:09 PM
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Re: BAD FUEL PUMP?????

Not sure if fan is working come to think of it. gonna go check that tonight, i feel kinda like an idiot for not checking in the first place. relay doesnt looked burned or anything but still hoping thats the problem. if the fan is also gone would that just mean that the ground for that relay isnt connected?
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Old Jul 2, 2010 | 11:05 AM
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Re: BAD FUEL PUMP?????

Fans not working with car on run, is fan supposed to run even when engine is cold? if so what does this mean?
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Old Jul 2, 2010 | 12:05 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

Fan will not run with cold engine - UNLESS - you turn the A/C on. You have the single fan correct? If you have the single fan, it will run always with A/C on. If fan doesn't run with A/C on, then check the fan motor by applying 12v directly to it (and a ground of course) - you can do this at the connector on the fan motor, or tie into the wires running to it. If it runs with a direct voltage applied to it, then maybe the relay is bad.
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Old Jul 2, 2010 | 02:09 PM
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Re: BAD FUEL PUMP?????

yes i have single fan but no a/c
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Old Jul 2, 2010 | 02:29 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

On pass side head between plugs #6 and #8 is the fan switch - unplug the connector and ground it - the fan should run with key on - that will let you know the fan and the relay are working. Then get the car hot and see if it comes on - should come on before you reach 225-230. If not, then maybe fan switch is bad.
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Old Jul 2, 2010 | 02:31 PM
  #12  
camaronewbie's Avatar
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: BAD FUEL PUMP?????

Sorry - the fan switch gets hot and provides the ground for the relay - thus grounding the fan switch wire does the same so you can test fan and relay for functionality.
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Old Jul 13, 2010 | 01:09 PM
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Re: BAD FUEL PUMP?????

So i changed the relay and she still wont go, anything else i can check before i start dropping the axle????? please let there be something else, im not gonna cut a hole in the trunk by the way. thanks
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