What is procedure for testing fuel pressure?
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Le Mans Master
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What is procedure for testing LT1 fuel pressure?
Okay, I came up with a fuel pressure test gauge.
I'll have it to play with all day Sunday.
What is the procedure to follow to test the fuel pressure on an LT1? And if anyone could pass along the OEM psi specs for vacuum line attached to FPR and the psi spec for when vacuum line pulled off FPR that would be fantastic.
:flag
[Modified by Lone Ranger, 4:31 PM 4/23/2003]
I'll have it to play with all day Sunday.
What is the procedure to follow to test the fuel pressure on an LT1? And if anyone could pass along the OEM psi specs for vacuum line attached to FPR and the psi spec for when vacuum line pulled off FPR that would be fantastic.
:flag
[Modified by Lone Ranger, 4:31 PM 4/23/2003]
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From: Sachse Texas
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Re: What is procedure for testing LT1 fuel pressure? (Lone Ranger)
At idle, with the vacuum attached, you should see around 36-38psi. With it diconnected, it should be anywhere between 42-47psi.
The other test other than just checking the pressure is to see how long the pressure takes to bleed off once the car is shut down. It should hold the majority of the pressure for at least 30 minutes with very little bleed down. If th presure drops immediately (within 2-3 seconds), then the check valve in the pump is the most likely candidate. If it slow bleeds, then the regulator or fuel injectors may be to blame (10 seconds-10 minutes). This is just based on my experience, and other may have different opinions though.
The other test other than just checking the pressure is to see how long the pressure takes to bleed off once the car is shut down. It should hold the majority of the pressure for at least 30 minutes with very little bleed down. If th presure drops immediately (within 2-3 seconds), then the check valve in the pump is the most likely candidate. If it slow bleeds, then the regulator or fuel injectors may be to blame (10 seconds-10 minutes). This is just based on my experience, and other may have different opinions though.
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From: Sun City West Az
Re: What is procedure for testing LT1 fuel pressure? (Vette92)
I asked the same pressure drop questions of Rich @ Cruizin Performance (via email) after he cleaned my injectiors. The numbers he supplied for drop rates for the 92 is a little different than the above post. If you like, I can forward a copy of his email to you with his take on things.
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Re: What is procedure for testing LT1 fuel pressure? (ittlfly)
I asked the same pressure drop questions of Rich @ Cruizin Performance (via email) after he cleaned my injectiors. The numbers he supplied for drop rates for the 92 is a little different than the above post. If you like, I can forward a copy of his email to you with his take on things.
[Modified by Lone Ranger, 5:33 PM 4/23/2003]
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Re: What is procedure for testing LT1 fuel pressure? (ittlfly)
Okay, ittlfly said it was okay for me to post the tech answer he got from Rich at Cruzinperformance, so here it is:
Yes, a static pressure test is performed both before and after cleaning and the injectors are tested at 80psi which is almost double the normal operating pressure. Yours passed with no problems.
It's not uncommon for the fuel pressure to drop after the pump shuts off and if it holds at 22psi for an extended period of time there should be no problems. If it were to drop completely to zero immediately or within a couple of minutes after the pump stops then the pressure would be escaping either through the injectors, the pressure regulator or the check valve in the fuel pump. The way to determine where it is going is to pressurize the system and "pinch" off the feed and return hoses isolating the individual components.
All vehicles lose fuel pressure when the pump is off. That is why the computer turns the pump on when you first hit the key. This "primes" the system so there is pressure to the injectors on initial start up. If the fuel system could hold pressure all the time, there would be no need for this initial "priming" before the engine is running.
In a nutshell, the fact that yours is dropping slowly and then holding is normal and shouldn't be a problem.
Yes, a static pressure test is performed both before and after cleaning and the injectors are tested at 80psi which is almost double the normal operating pressure. Yours passed with no problems.
It's not uncommon for the fuel pressure to drop after the pump shuts off and if it holds at 22psi for an extended period of time there should be no problems. If it were to drop completely to zero immediately or within a couple of minutes after the pump stops then the pressure would be escaping either through the injectors, the pressure regulator or the check valve in the fuel pump. The way to determine where it is going is to pressurize the system and "pinch" off the feed and return hoses isolating the individual components.
All vehicles lose fuel pressure when the pump is off. That is why the computer turns the pump on when you first hit the key. This "primes" the system so there is pressure to the injectors on initial start up. If the fuel system could hold pressure all the time, there would be no need for this initial "priming" before the engine is running.
In a nutshell, the fact that yours is dropping slowly and then holding is normal and shouldn't be a problem.
