Adjusting fuel pressure
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Adjusting fuel pressure (Sliding)
Not really. The fuel pump is only activated for 1-1/2 to 2 seconds when you turn the ignition key to "on". If the ECM doesn't get a distributor pulse signal within that time period, the fuel pump shuts down.
Also, cranking the engine long enough for the oil pressure switch to re-activate the fuel pump isn't a good idea either.
I wouldn't trust, as being accurate, the fuel pressure gauge's ability to hold the pressure once the pump shuts down.
TPIS says GM calls for a stock fuel pressure setting of 41-47 psi for the 90 5.0 & 5.7 engines; LT-5, 48-55. Myron says the higher end is better.
Jake
[Modified by JAKE, 11:20 AM 5/16/2004]
Also, cranking the engine long enough for the oil pressure switch to re-activate the fuel pump isn't a good idea either.
I wouldn't trust, as being accurate, the fuel pressure gauge's ability to hold the pressure once the pump shuts down.
TPIS says GM calls for a stock fuel pressure setting of 41-47 psi for the 90 5.0 & 5.7 engines; LT-5, 48-55. Myron says the higher end is better.
Jake
[Modified by JAKE, 11:20 AM 5/16/2004]
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Adjusting fuel pressure (Sliding)
You need to install a fuel pressure gauge and check the pressure setting with the stock FPR and the engine running before making the swap.
Then install the new AFPR and make any needed adjustment.
Jake
[Modified by JAKE, 11:27 AM 5/16/2004]
Then install the new AFPR and make any needed adjustment.
Jake
[Modified by JAKE, 11:27 AM 5/16/2004]
Drifting
Joined: Nov 2001
Posts: 1,783
Likes: 2
From: Latham NY
Re: Adjusting fuel pressure (Sliding)
Can I adjust fuel pressure while engine is not running?
What is stock FP for '90 L-98?
What is stock FP for '90 L-98?
ALDL pins are arranged:
FEDCBA
G
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Adjusting fuel pressure (Bluevette85)
Can I adjust fuel pressure while engine is not running?
What is stock FP for '90 L-98?
Yes you can. Apply 12 volts to pin G of the ALDL. I run a wire from the battery + to pin G. Set my fuel pressure last night this way.
ALDL pins are arranged:
FEDCBA
G
What is stock FP for '90 L-98?
Yes you can. Apply 12 volts to pin G of the ALDL. I run a wire from the battery + to pin G. Set my fuel pressure last night this way.
ALDL pins are arranged:
FEDCBA
G
I believe there are additional ways, too, using a jumper. Like applying 12 volts directly to the pump and maybe even the relay.
I don't know if those are the recommended ways to set the pressure though. In any event, it's necessary to have a fuel pressure gauge; otherwise, there's no way of knowing the pressure setting.
Jake
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Adjusting fuel pressure (Sliding)
Sliding, if you check/adjust fuel pressure with the engine running at idle be sure the vacuum line is disconnected from the FPR/AFPR.
Then set the AFPR to that pressure and adjust for best WOT performance.
Then set the AFPR to that pressure and adjust for best WOT performance.
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