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fuel pressure

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Old Feb 8, 2010 | 04:07 PM
  #1  
transamice's Avatar
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Joined: Apr 2005
Posts: 490
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From: Hamilton ON Canada
Car: 87 GTA t-top
Engine: L98 350 w/RMT
Transmission: 700R4
Axle/Gears: 9 bolt BW 3.45
fuel pressure

When you turn the key to on without cranking, what should the fuel pressure be at, should it stay at the pressure or is it suppost to drop fast?
My 87 GTA 350TPI starts with a pressure of 35 and at idle is down to 30-35 psi, when revved it goes upto 43psi.
Is this normal, just trying to figure out why my idle isnt consistant and sux.

Last edited by transamice; Feb 8, 2010 at 05:16 PM.
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Old Feb 8, 2010 | 05:44 PM
  #2  
five7kid's Avatar
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Joined: Mar 2000
Posts: 43,187
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
The fuel pressure regulator has a vacuum line on it to drop the pressure at idle/high manifold vacuum conditions. It should be higher when the engine isn't running or when you put the engine under load, and should maintain pressure when the pump shuts off when the engine isn't running. If it doesn't maintain pressure, it could be from a leaking regulator, leaking check valve in the fuel pump, or leaking injectors.
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Old Feb 8, 2010 | 05:57 PM
  #3  
transamice's Avatar
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Joined: Apr 2005
Posts: 490
Likes: 1
From: Hamilton ON Canada
Car: 87 GTA t-top
Engine: L98 350 w/RMT
Transmission: 700R4
Axle/Gears: 9 bolt BW 3.45
Re: fuel pressure

The pump, filter, injectors, afpr are all a year old.
I have checked for leaks but I might be missing something and come to think of it, I do smell a faint bit of gas from the drivers side when I throttle it.
Nothing else comes to mind of anything else thats not normal.
Its just to dam cold here to work on the car.
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Old Feb 12, 2010 | 03:27 PM
  #4  
bambino's Avatar
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Joined: Oct 2007
Posts: 21
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From: Nor Cal 95215
Car: 1990 IROC-Z
Engine: LB9
Transmission: 700R4
Axle/Gears: 2:73
Re: fuel pressure

should the vacuum hose be disconnected, when checking fuel pressure?
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