Hello everyone, I'm having an issue with a 92 Z28 that I received from a friend. The car has a 355 TPI, along with nice supporting mods. The thing that brings me here today ,for the first time in probably 10 years, is that Im having quite a rough time trying to figure out what is going on with the electronics regarding my fuel system.
When I key on the ignition, the fuel pump does not prime, and obviously doesn't build fuel pressure. when I crank the engine, I get fuel pressure and the car will start eventually.
The auxiliary cooling fan also constantly runs with the key in the on or running position. (Not sure if related)
Also, I've been looking for the G terminal on the ALDL connector to supply power to the pump, but I do not see it, my guess is that the wires/ terminals are scrambled, does anyone have a picture of the back of their ALDL connector?

 

Have you checked the secondary fan switch for being grounded ( located in the passengers side head).
You can check to see if the ecm is powering the pump relay for prime.

 

Not all applications have g in the aldl.

 

I'm going to check said ground when I get home from work today. Also, just to be sure, which relay is the fuel pump relay? I see that there are several in a bunch near the brake booster.

 

It might be located as pictured. It might also have a red lead hanging off if that’s a direct lead to the pump.




Disregard the red arrow (image from the internet).

 

Does pressure hold after engine is off?

 

The fuel pressure starts to drop slowly about 5 minutes after I shut down the engine, There will be no pressure in the line over night.

 

Almost sounds like the fuelpump relay has died and its relying on the oil psi switch to see oil psi (when cranking) to close the secondary fuelpump circuit?

The fuel pump will only prime once. (yours not even once cold with koeo?) If you hit the key twice quickly without cranking the second time it won't prime. You have to wait for several seconds for it to prime again

 

A little update from yesterday because I got caught in the rain while trying to continue the diagnosis.
I found why the cooling fan is constantly on, a previous owner had cut the fan switch plug off the end of the wire and soldered it to a brake line ( I wish I was kidding).

 

I assume this is part of the problem, but I can't rule out that a previous owner hasn't hacked a wire somewhere, so I have to do a bit of back tracing on the wiring to be sure there's no funny business.

Should the car run with the fuel pump relay disconnected?