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fuel pressure and fuel pump question

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Old Mar 30, 2012 | 11:48 PM
  #1  
resop27's Avatar
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From: Wentzville Mo
Car: 89 325is, 91 z28
Engine: 2.5l 6, l98
Transmission: t56
Axle/Gears: 3:42
fuel pressure and fuel pump question

Well Ive been having a surging idle problem and some other issues running. Well I checked the fuel pressure and at prime its right about 40 psi (this is with the regulator) and when It starts its a constant 30 psi, sometimes itll go to 38-40 for a mere second but Itll go as low as a 28.


The fuel pump is about 2 years old but hasnt been used in over a year? could it have gone bad?
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Old Apr 2, 2012 | 06:54 PM
  #2  
seawolf18's Avatar
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From: South Dakota
Car: 91 Trans AM
Engine: 305 TPI
Transmission: T-5
Axle/Gears: 3.42
Re: fuel pressure and fuel pump question

Take the vaccum line off the pressure regulator and see if it smells like gas. If it does then the regulator is bad. Factory GM fuel pressure is 43.5 PSI. Hook up the gauge and see if it holds pressure or bleeds down right away. It should hold pressure for hours.
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Old Apr 2, 2012 | 09:09 PM
  #3  
jeff_blake's Avatar
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From: Mountlake Terrace, Wa
Car: 86 Iroc + 83 Firebird
Engine: Iroc 305 TPI, Firebird 305 4bbl
Transmission: 700r4 in both.
Axle/Gears: Iroc 3.27 Firebird 3.23
Re: fuel pressure and fuel pump question

28's pretty low. id assume a bad fuel pressure regulator. tpi's have them passenger side, near the pressure valve. if i remember correctly you have to take the plenum off to replace it.
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