Car doesn't hold fuel pressure
03-15-2008, 11:34 PM
#1
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Location: Kalamazoo Area, Michigan
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Car doesn't hold fuel pressure
If someone could help me figure this out that would be great.
I have a 94 Z28 and when I turn on the key I can hear the fuel pump come on and the car builds fuel pressure. Then after a couple of seconds it drops to zero. What is was thinking is that either the afpr or injectors are bad. So I unbolted the fuel rails with the injectors still in and turned on the key, I didn't see any fuel leaking out of the injectors. So I figured it has to be the afpr or something else, but I don't have a clue.
I have a 94 Z28 and when I turn on the key I can hear the fuel pump come on and the car builds fuel pressure. Then after a couple of seconds it drops to zero. What is was thinking is that either the afpr or injectors are bad. So I unbolted the fuel rails with the injectors still in and turned on the key, I didn't see any fuel leaking out of the injectors. So I figured it has to be the afpr or something else, but I don't have a clue.
03-16-2008, 09:51 AM
#5
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At idle, with the vacuum line disconnected, GM requires that the pressure be between 41-47psi. 43.5psi is the "design" pressure. When you reattach the vacuum line, rail pressure will drop proportional to intake manifold vacuum, anywhere from 4 - 8psi drop, depending on the camshaft. At WOT, the pressure should hold within 2psi of the "no vacuum" idle pressure.
It doesn't take much of a leak in the system or in the pump check valve for the pressure to drop rapidly when the engine is not running.
It doesn't take much of a leak in the system or in the pump check valve for the pressure to drop rapidly when the engine is not running.
03-16-2008, 10:37 AM
#6
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It acts like it leaks into the intake somewhere, I have had to do flood recovery mode a couple of times to get it to start. You can smell fuel real bad in the engine bay.
It also has an Aeromotive afpr and C5 Z06 injectors if that matters any.
It also has an Aeromotive afpr and C5 Z06 injectors if that matters any.
03-16-2008, 05:15 PM
#7
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Location: Eagle River, Alaska
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aeromotive fpr's don't hold pressure. It is normal for them to fall to 0 psi after the pump turns off. It is anoying, I talked to aeromotive about it once. They said they couldn't get them to flow as well with them holding pressure. That is also the reason they don't have a CARB #
03-16-2008, 07:17 PM
#8
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Location: Kalamazoo Area, Michigan
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aeromotive fpr's don't hold pressure. It is normal for them to fall to 0 psi after the pump turns off. It is anoying, I talked to aeromotive about it once. They said they couldn't get them to flow as well with them holding pressure. That is also the reason they don't have a CARB #
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