'91 w/L98... is the fuel pump located on the firewall with the fan relays? I can't remember, but thinking i'm gonna have to change it, cuz the pump runs intermittently when i shut the engine off, instead of running steady before it shuts off completely... thanks...

KAM

 

Should be with the other relays on the firewall next to the brake booster.

 

The fuel pump relay is a more squared relay as opposed to the fan relay or the MAF(if so equipped)power and burnoff. Before you replace it try cleaning the socket and contact pins.

 

It's the middle of the three attached to the firewall. I spliced in a heated three wire O2 sensor.

 

OK - I replaced the relay... next question I have is... when the engine is shut off, is the pump supposed to run for a few seconds or shut off upon engine shutdown? This is similar to the issue I started with, meaning that now when I shut the engine off, the pump shuts off. Before when I shut it down, the pump still ran for a few seconds, but was intermittent. On my IROC, the pump on it runs for a few seconds after shutdown, so... with this new relay in my '91, it shuts off when I shut the engine down...

KAM

 

Two things supply voltage to the pump when the car is running. The oil sender unit has a switch that closes after approx 5lbs of oil pressure and supplies 12 volts to the pump as well as the fuel pump relay. The relay comes on when the key is turned to the ON position and primes the fuel rail, shuts down then re-energizes when the car starts. A sticky relay could have causes it to run after the cars was off, or possibly the oil sender mounted switch could have been staying on. The pump should shut off when the engine is killed. Funny you mention this, my 89 every once in a while did the same thing. I replaced the relay and the sender switch and I have not noticed the problem. I suspect that just maybe the oil sender switch was a little slow to turn off, I don't think it's an issue you should worry much about unless it runs for any length of time.

 

the amount of time the pump runs has cut down drastically since i changed the relay, but now i'm thinking my '90 IROC has the same problem because it runs a considerable amount of time after engine shut down. i thought before that the reason the pump continued to run after shut down was to maintain pressure on the system, whatever purpose that may serve, cuz like as you say, when the key is turned on, the pump primes up the system. now on my IROC, it runs with high oil pressure constantly when the engine is on, so that switch may be causing that issue. i'll have to really take a look at both cars and compare notes. thanks for your responses...

KAM