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fuel pump stays on?

Old Jan 13, 2011 | 02:22 PM
  #1  
Red 87 GTA's Avatar
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Joined: Jul 2010
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From: NJ
Car: 87 GTA flame red
Engine: 5.7 l98 cranes 2032 and chip
Transmission: stage 10 700r4
Axle/Gears: 3.27 axle
fuel pump stays on?

after i shut my car down and turn my key all the back the fuel pump stays on for almost 10 seconds this recently started and its only when i turn the car off in pre-start its fine it only kicks in for 2-3 seconds
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Old Jan 13, 2011 | 02:28 PM
  #2  
Gumby's Avatar
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Joined: Oct 2001
Posts: 8,113
Likes: 6
From: NWOhioToledoArea
Car: 86-FireBird
Engine: -MPFI
Transmission: T5
Axle/Gears: 3:42
Re: fuel pump stays on?

Id say so??? 10sec on is just long enough to rebuild pressure.

long as it shuts off after 10, big whoop. when its on for more then a 60sec start to worry.
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Old Jan 13, 2011 | 05:28 PM
  #3  
camaronewbie's Avatar
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Joined: Sep 2002
Posts: 9,192
Likes: 20
From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: fuel pump stays on?

Try replacing the Oil Pressure Sending Unit. It has a direct connection from battery to the fuel pump, thus it can go bad in such a way that it 'thinks' it's reading oil pressure when it's not, and thus it will turn the pump on anytime the ECM is not running the pump and it senses oil pressure. It can (and has on my car) run the fuel pump 24/7 until the battery dies - even with the key in your pocket.

Many folks think (wrongly) that the OPSU is a safety off switch - it's not - it's a safety on switch - it will run the fuel pump so that you can limp home in the event that the ECM or fuel pump relay go bad. This is why when folks swap to a carbed motor they will still have a running fuel pump, even with the ECM yanked out of the car.
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Old Jan 14, 2011 | 05:23 PM
  #4  
Red 87 GTA's Avatar
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Member
 
Joined: Jul 2010
Posts: 305
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From: NJ
Car: 87 GTA flame red
Engine: 5.7 l98 cranes 2032 and chip
Transmission: stage 10 700r4
Axle/Gears: 3.27 axle
Re: fuel pump stays on?

i think its just having a problem getting fuel press but the pump sounds healthy. it just runs for like 8 secs then it gets that building press sound and then shuts off
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Old Jan 16, 2011 | 09:37 PM
  #5  
emilde's Avatar
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Joined: Oct 2010
Posts: 9
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From: muscoda wisconsin
Car: 1986 pontiac trans am
Engine: 305 t.p.i (for now)
Transmission: 700-r4
Re: fuel pump stays on?

i agree with camaronewbie, sounds like the o.p.s.u might be hanging up when u shut the car off. id just keep an eye on it and if it starts to run-on longer after u shut it off id replace the o.p.s.u........
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Old Jan 17, 2011 | 04:07 AM
  #6  
DRIVE2FAST's Avatar
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Joined: Sep 2009
Posts: 598
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From: PHOENIX/ TOLLESON ARIZONA
Car: 90 IROC 5.7 1LE CLONE 89 GTA 88IROC
Engine: 5.7TPI / 5.7TPI/ 5.7TPI/ 4.3 CMFI
Transmission: 700R4 UPGRADED 700R4STOCK700R4STOCK
Axle/Gears: 3.23 10 BOLT 3.27 9 BOLT 2.77 9BOLT
Re: fuel pump stays on?

CHECK THE ELECTRICAL SCHEMATICS FOR THE FUEL SYSTEM . I HAD A PUMP RELAY THAT FAILED. I FLICKED IT A FEW TIMES AND IT CLOSED AGAIN. RAN HOT BUT LONG ENOUGH TO GET HOME.
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