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Fuel pressure drops fast!!

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Old Jul 15, 2011 | 05:14 PM
  #1  
joeyspagz's Avatar
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From: New York
Car: 88 Firebird Trans Am
Engine: 305 tpi
Transmission: 700r4 shift kit
Axle/Gears: Posi
Fuel pressure drops fast!!

i just tested my fuel pressure and it went to 40 psi then to 20 psi in about 1 minute. my car does run and idle. Leaky injector or something else???
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Old Jul 15, 2011 | 05:42 PM
  #2  
joeyspagz's Avatar
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Posts: 122
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From: New York
Car: 88 Firebird Trans Am
Engine: 305 tpi
Transmission: 700r4 shift kit
Axle/Gears: Posi
Re: Fuel pressure drops fast!!

Just tested it again and this is what i got

PSI............Time
40-35
35............. :46
30............. 1:18
325.............2:09
20............. 3:26
15............. 5:13
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Old Jul 16, 2011 | 09:33 AM
  #3  
joeyspagz's Avatar
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Joined: Apr 2011
Posts: 122
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From: New York
Car: 88 Firebird Trans Am
Engine: 305 tpi
Transmission: 700r4 shift kit
Axle/Gears: Posi
Re: Fuel pressure drops fast!!

not even one person
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Old Jul 16, 2011 | 11:01 AM
  #4  
3rdgenfamily's Avatar
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Joined: Sep 2007
Posts: 37
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From: Gainesville GA
Car: 91' Z28
Engine: 383 TPI, 2-305 TBI, 305 TPI
Re: Fuel pressure drops fast!!

Check your pressure into the rail at the fuel line connections. Sounds like you need to replace the fuel filter.
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Old Jul 16, 2011 | 01:11 PM
  #5  
skibum2100's Avatar
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Joined: May 2010
Posts: 259
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From: Boulder Colorado
Car: 1988 GTA
Engine: 5.7 TPI w/ Bosch III's
Transmission: T56
Axle/Gears: 3.27 Borg Warner 9 bolt
Re: Fuel pressure drops fast!!

Is that after you turn the engine off? If so, that doesn't sound like a terrible drop in fuel pressure. When my injectors and diaphragm were leaking, the pressure dropped instantly. You could check your fuel pressure regulator diaphragm for a tear by pulling the vacuum line off the regulator body. If it smells like fuel there is a leak.
I couldn't find a way to test my injectors so I pulled my fuel rail up a little bit and left the injectors installed in the rail, then put some paper towels under the bottom of the injectors. Energize the pump to pressurize the rail and check for any wet spots on the paper towels under the injectors. I had 4 leaky injectors.

Hope this helps.
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Old Jul 16, 2011 | 02:04 PM
  #6  
joeyspagz's Avatar
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Joined: Apr 2011
Posts: 122
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From: New York
Car: 88 Firebird Trans Am
Engine: 305 tpi
Transmission: 700r4 shift kit
Axle/Gears: Posi
Re: Fuel pressure drops fast!!

ok it doesnt sound like the injectors right? ill check the fuel pressure regulator on Monday. thanks
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Old Jul 17, 2011 | 01:09 AM
  #7  
skibum2100's Avatar
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Joined: May 2010
Posts: 259
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From: Boulder Colorado
Car: 1988 GTA
Engine: 5.7 TPI w/ Bosch III's
Transmission: T56
Axle/Gears: 3.27 Borg Warner 9 bolt
Re: Fuel pressure drops fast!!

Hang on. Dont rule out the injectors yet, they could be all or part of the problem.
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