formcam

Should the fuel pump ever cycle for more than 4 to 8 seconds after the ignition has been off? Its a tpi car.

GMTech

No. It shouldn't stay on any longer than like 2 seconds due to the oil pressure in the engine bleeding off. As long as there is at least 4 psi, the contacts in the oil pressure switch will close. If it is staying on excessively, you may have a bad switch. If it stayed on for 2-4 seconds, I might not worry as much, but if it stayed on for more than that, I would be concerned.

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ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks

'97 Bonneville SSE

blak92!

I thought the fuel pump cycled after the ignition was shut off on extremely cold days to increase the temperature of the fuel (reduce the density). The process was for cleaner, immediate restarts.

Every fuel injected GM car I have owned has "cycled" the fuel pump only on very cold days.

GMTech

Don't know about that. That kinda don't make sense, because it isn't uncommon for fuel pressure to bleed down over the course of the night so that would be pointless, plus the 2 second initial prime when the key is first turned on is supposed to aid startup. You may be right, but I guess living in Georgia, you don't see that to much.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks

'97 Bonneville SSE

blak92!

My experience:
When it is extremely cold, turning the key to the on postion primes the fuel pump for a good few seconds longer than than the usual 2 seconds.

For example, (on extremely cold days) the fuel pump only 'cycles' when the car is shut off when pulling the car from the driveway to the garage, it will stay on for an extra few seconds longer. but for longer trips the fuel pump will shut off when the car is shut off, I guess because the fuel is not as cold.

I know I am not clear explaining this, perhaps someone could find out exactly?

GMTech? any buddies from up North who might know?
Next time I am at the local dealership, I will inquire.

TomP

I've seen that too... when I move my dad's front-wheel-drive 2.8 multiport around the yard. (It only runs for 2 minutes, tops.) When I turn it off, the pump hums along for a few seconds after the motor dies.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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eatmydust

My 86 IROC does this too. Sometimes when I shut it off I can get out of the car and hear the fuel pump shutting off or whatever for about a good, 4-6. But only when I just start it and don't drive it. When I drive it, goes off after about 2-3 seconds when shut off. If it is some switch, were is it located and how easy are they to put in and stuff?

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86' IROC-Z
5.0L TPI