Fuel Pump constantly on.....???

[Sr20Crazy]

just finish my notch top swap into my S14. before swapping out the engine, the fuel pump would prime for about 3-5 secs and stop in the on position. but after i got the swap done, the fuel pump would stay on. I've check the wiring and found a few post that stated i should check the plug to my alternator. unplugged, inspected, reinstall my alternator plug and still having the same issues. Anyone have this problem? trying to figure this thingamajig out before i have to bring it to the shop.

[cotbu]

Try the fuel pump relay. If not bad check the ecu for shorted pins. 104 iirc

[Noobles]

Check the earths, you might find earthing the ground at the fuel pump to the body can fix this.

Seen it a few times on S13's.

[Sr20Crazy]

check all that. pulled the ECU off and fuel pump still acting the same.. any other inputs??

[zombiewolf513]

It still runs with the relay pulled out? There isn't much more to the circuit than what has been pointed out...

I concur with cotbu, if pin 104 is shorted, it'll be constantly activating the relay. You could also have the wire going to pin 104 from the relay nicked and grounded, which would produce the same effect. That is... if the relay isn't broken.

http://s31.postimg.org/rpnlk9vln/Fuel_Pump_Wiring.png

[hanzbrady]

Also check for chassis harness damage, I rubbed through the harness under my left wheel well and it caused this, as well as many other wiring issues.

[Sr20Crazy]

check all the 5 groundings in the engine bay. pulled the fuel pump relay off and it was not send fuel. ohm the relay with and without power. checked out good. replace it with anther relay. still having the same issue. check the pin on the ECU, nothing bad on it.

[zombiewolf513]

Then the wire going to pin 104 from the relay is split and grounded somewhere.

Ive never had an ecu ground out the 104 pin before, but i think it would be internal to the ecu and probably not something you could visually confirm from just looking at the pin. Probably. But idk for sure