Correct fuel system priming parameters?
Thread Starter
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Joined: Dec 2005
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From: Kailua-Kona, HI
Correct fuel system priming parameters? Can someone explain to me a properly functioning LT1 fuel system's paramaters?
I.E.:
When you put the key forward how many seconds should the pump prime for?
If you prime the system, then immediately turn the key OFF, then turn it back on, should it prime again? Over and over? Or does the car wait a few seconds before allowing the system to prime again?
Also, what would cause a car to not start with the key forward and turning over, but when you let off the key it starts to fire and will only start with the pedal to the floor?
I am having a hell of a time fixing this issue on my 95 Z28.
I.E.:
When you put the key forward how many seconds should the pump prime for?
If you prime the system, then immediately turn the key OFF, then turn it back on, should it prime again? Over and over? Or does the car wait a few seconds before allowing the system to prime again?
Also, what would cause a car to not start with the key forward and turning over, but when you let off the key it starts to fire and will only start with the pedal to the floor?
I am having a hell of a time fixing this issue on my 95 Z28.
Thread Starter
TECH Regular
Joined: Dec 2005
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From: Kailua-Kona, HI
Unfortunately that doesn't answer my question.
I don't need to know what the pressure is / is supposed to be, since you can hear the pump prime the system regardless of the pressure. I want to know for how many seconds is the pump supposed to primer the system, and if I was to turn the key off, and turn back on right afterwards, should it prime the system again?
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Is the pump easy to hear on these cars? I never hear my pump prime but that doesnt mean that it doesnt. I do believe I have a fueling issue on my car as well as it never seems to run right all of the time when I start it. The car isnt done yet so I have not done any driving with it as of now.
I have to figure out where/how to test the fuel pressures on my 93 as I only see the 94-97 referenced with a Shraeder Valve.
Joe
I have to figure out where/how to test the fuel pressures on my 93 as I only see the 94-97 referenced with a Shraeder Valve.
Joe
Just because you hear the pump run doesn't mean you have correct pressure.
Just turn the key off for a couple of seconds. If you flick it off then right back on without a pause, the computer will sort of stay energized and you won't get another prime out of it.
starts after you let off the key? sounds like something is botched up with the wiring where the pump isn't on durring the "start" positoin but is on durring the "run" position.......maybe a bad keyswitch monitor the +12V to the pump while somebody cranks the motor and make sure it stays on
The computer grounds the fuel pump relay which then supplies 12 volts to the fuel pump. The pcm operates the injectors by grounding them.
Thread Starter
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Joined: Dec 2005
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From: Kailua-Kona, HI
Thanks for the info guys.
My FP is priming correctly per your answers. It will prime for 3-4 seconds, and it does prime every time I cycle the key, but it needs to be in the off position for 4-5 seconds before I can turn the key forward again and get another prime out of it.
Now I have to check my pressures one last time before I move back to the ignition system.
Damn car wont start when cold, but will fire 10 times in a row with no coaxing after its been running for 5-10 mins. When it runs it runs great, especially since I just changed the OPTI.
My FP is priming correctly per your answers. It will prime for 3-4 seconds, and it does prime every time I cycle the key, but it needs to be in the off position for 4-5 seconds before I can turn the key forward again and get another prime out of it.
Now I have to check my pressures one last time before I move back to the ignition system.
Damn car wont start when cold, but will fire 10 times in a row with no coaxing after its been running for 5-10 mins. When it runs it runs great, especially since I just changed the OPTI.
Thread Starter
TECH Regular
Joined: Dec 2005
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From: Kailua-Kona, HI
I have changed out the water temp sensor on the water pump housing already, haven't changed the intake sensor.
Where can I get a decent OBD1 scan tool that will give me live data?
