Fuel pump issue
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Fuel pump issue
I have gone through a ton of post on here and red just about all of them. The car turns over but the fuel pump will not prime or turn on for that matter. I have checked the inline fuse by the battery. That is good. I replaced the relay today with no luck there either. I went and checked the fuse under the dash and that was good. The oil pressure sensor is new and hooked up next to the distributor. The oil temp sensor that goes above the oil filter is not installed yet. It's on order and I have the hole plugged. I don't think that will cause the problem? The motor is a fresh rebuild and I have just added all the fluids and am trying to fire it for the first time. I did find a couple wires that are cut. Not sure where they go. Here are a couple pics.
Thread Starter
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Joined: Jul 2013
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
This is at the firewall by the heater box. Has a inline fuse that is blown. Can't see anywhere it was cut from.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Fuel pump issue
Would at least give a direction to look for your fault
Once you have confirmed 12v available on the org wire at the relay ,jumpering that wire to the tan /wht wire in the connector should make the pump run.
If it doesn't you have a problem with the pump or the wiring from relay to pump
That is the fuel pump ( OP ) switch, that operates the fuel pump as backup if the relay is not working. See diagram below
If you had that installed now then the pump would run when you crank the engine over even with no relay ( assuming pump is good )
Thread Starter
Junior Member
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Joined: Jul 2013
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
Vette, thanks for the response. I will check voltage tomorrow. I wasn't aware the oil temp sensor had anything to do with the fuel pump. I knew the oil pressure sensor did. The temp sensor I ordered through auto zone. It was the only one listed for my car and was special order.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Fuel pump issue
3rd Gens usually have the OP switch for the pump above the oil filter
You have a sensor for the OP gauge ( 1 wire ) and a OP switch (2 wire ) for the pump
Thread Starter
Junior Member
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Joined: Jul 2013
Posts: 78
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
That's where I might be getting things mixed up. Op gauge sensor is next to the distributor and I'll need the switch not a temp gauge. I will have to order one tomorrow and see what happens. I'm still going to use a DVM and see what I get. Again thanks for the help.
Thread Starter
Junior Member
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Joined: Jul 2013
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
Better to get a DVM and check to see what ( if any ) power you have on which relay terminals.Check to see if the grounds are good.
Would at least give a direction to look for your fault
Once you have confirmed 12v available on the org wire at the relay ,jumpering that wire to the tan /wht wire in the connector should make the pump run.
If it doesn't you have a problem with the pump or the wiring from relay to pump
I have checked to make sure that there is power both at the org wire and have 12.34v there. I have also checked the fuse and have the same there.
Hope you bought the correct unit ?
My (OP) switch came in and it doesn't thread into the hole. Can u point me in a direction it getting the proper one?
That is the fuel pump ( OP ) switch, that operates the fuel pump as backup if the relay is not working. See diagram below
If you had that installed now then the pump would run when you crank the engine over even with no relay ( assuming pump is good )
I believe the pump is bad. I have gone a far as jumping 12 from ign wire to the obdi port under the dash. Still nothing. Looks like I have to replace the pump. Do you have a rec on brand and a place to buy?
Would at least give a direction to look for your fault
Once you have confirmed 12v available on the org wire at the relay ,jumpering that wire to the tan /wht wire in the connector should make the pump run.
If it doesn't you have a problem with the pump or the wiring from relay to pump
I have checked to make sure that there is power both at the org wire and have 12.34v there. I have also checked the fuse and have the same there.
Hope you bought the correct unit ?
My (OP) switch came in and it doesn't thread into the hole. Can u point me in a direction it getting the proper one?
That is the fuel pump ( OP ) switch, that operates the fuel pump as backup if the relay is not working. See diagram below
If you had that installed now then the pump would run when you crank the engine over even with no relay ( assuming pump is good )
I believe the pump is bad. I have gone a far as jumping 12 from ign wire to the obdi port under the dash. Still nothing. Looks like I have to replace the pump. Do you have a rec on brand and a place to buy?
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Thread Starter
Junior Member
iTrader: (4)
Joined: Jul 2013
Posts: 78
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
Better to get a DVM and check to see what ( if any ) power you have on which relay terminals.Check to see if the grounds are good.
Would at least give a direction to look for your fault
Once you have confirmed 12v available on the org wire at the relay ,jumpering that wire to the tan /wht wire in the connector should make the pump run.
If it doesn't you have a problem with the pump or the wiring from relay to pump
Hope you bought the correct unit ?
That is the fuel pump ( OP ) switch, that operates the fuel pump as backup if the relay is not working. See diagram below
If you had that installed now then the pump would run when you crank the engine over even with no relay ( assuming pump is good )
Would at least give a direction to look for your fault
Once you have confirmed 12v available on the org wire at the relay ,jumpering that wire to the tan /wht wire in the connector should make the pump run.
If it doesn't you have a problem with the pump or the wiring from relay to pump
Hope you bought the correct unit ?
That is the fuel pump ( OP ) switch, that operates the fuel pump as backup if the relay is not working. See diagram below
If you had that installed now then the pump would run when you crank the engine over even with no relay ( assuming pump is good )
My (OP) switch came in and it doesn't thread into the hole. Can u point me in a direction it getting the proper one?
I believe the pump is bad. I have gone a far as jumping 12 from ign wire to the obdi port under the dash. Still nothing. Looks like I have to replace the pump. Do you have a rec on brand and a place to buy?
Thanks for your help.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Fuel pump issue
Or jumpering the 2 wire connector that fits the OP switch? ( the same effect as above , power direct from batt to the pump)
Thread Starter
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Joined: Jul 2013
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From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
I tried it both ways. I tried the g terminal to make sure the relay was good. I can hear it click when power is applied. It is a new relay as well but have seen them bad out of the box.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Fuel pump issue
it does not make the relay work work or test it's operation so there should be no sound.
Typical GM relay wiring ( not 3rd Gen ), observe where wire from G runs to ...
relay should only operate ( click) when the black / wht wire is grounded
Last edited by vetteoz; Oct 15, 2013 at 05:49 PM.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Thread Starter
Junior Member
iTrader: (4)
Joined: Jul 2013
Posts: 78
Likes: 0
From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
The G terminal puts power through the relay contacts when the relay is off to test the pump
it does not make the relay work work or test it's operation so there should be no sound.
Typical GM relay wiring ( not 3rd Gen ), observe where wire from G runs to ...
relay should only operate ( click) when the black / wht wire is grounded
it does not make the relay work work or test it's operation so there should be no sound.
Typical GM relay wiring ( not 3rd Gen ), observe where wire from G runs to ...
relay should only operate ( click) when the black / wht wire is grounded
Thread Starter
Junior Member
iTrader: (4)
Joined: Jul 2013
Posts: 78
Likes: 0
From: Buffalo, NY
Car: 1987 Iroc Z28
Engine: 305
Axle/Gears: 3.73
Re: Fuel pump issue
Vetteoz, thanks for all your help in this matter. I put a new fuel pump in this morning and was able to fire the car up. This was a great feeling after buying it with the motor on a pallet. Lol. Again thanks.
Keith.
Keith.
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