No ground to fuel pump relay

[abbythug]

Should start of by saying I recently picked up a 1990 xj

Having an issue I can't seem to diagnose, found a jumper to the ground wire of the fuel pump relay.

Without the jumper the relay won't turn on.

There was a bad connection and some bare wires around the relay plug (could wiggle the harness and the relay would click on and off), this has been fixed with a new plug.

Where would be the next place to look?
Electrical really stumps me so I'm having a hard time trying to figure this out.

 

[gdavis]

I'm guessing the previous owner used that jumper as a "kill switch". If you have fixed the bad connection with the new plug and secured the jumper wire to chassis or battery ground, will the jeep start & run ok?

 

[abbythug]

yes if the jumper is attached to a ground the jeep runs fine

 

[techno1154]

The ground to that relay is controlled by the PCM/ECM. The relay is usually energized for a few seconds when the key is turned on, i.e. ignition only, when cranking the engine as well as when the engine is running. If there is no ground present when the key is first turned on then it is trace wire time from the relay/fuse panel back to the PCM.

 

[old_man]

Just for educational purposes, I will explain that the reason the relay is controlled by the ECU is so that if the engine dies (wreck), even though the key is still in the on position, the fuel pump will stop spraying the hot engine with gas. :flame: