alright guys, this is a wierd one, my fuel pump used to come ON and stay ON as soon as i turned the key to the ON position, then just the other day, it didnt run, i was kinda worried. i listened and listened and couldnt hear it. its kinda loud cause its a high performance after market pump. so when i turn the key to START, and start the car, it runs and keeps going as per normal, what would cause this to happen. im wondering if one of the relays is bad, or if it isnt getting a signal from one of the sensors, but isnt keeping the pump from running. any ideas appreciated, cause its probly something stupid

 

I doubt it's the relay cause then it wouldn't work even when the car is running. After you let go of the key it goes back to 'ON' anyways. What year is the motor and wiring on it? The later years had the one relay controlled by the ECU. The earlier ones had 2-3 relays controlled by different things. Get under the dash and test to see if the relay is getting power while the key is 'ON' but the engine is not running.

 

Need the year because some 280zx have three fuel pump relays and the 1983 had only one fuel pump relay.

If it's a turbo 82 or newer, it will also have a fuel pump controller.

 

its a 79, and after you turn it over, the pump runs, but only if the engine starts, otherwise, i think it stays shut off.