Runaway Fuel Pump!!!

New problem for my 87 MJ. I had the - battery cable disconnected to do some work and when I re connected the cable the fuel pump continued to run, even with the key in my pocket and I could hear fuel circulating back to the tank? I had to leave the cable disconected to stop it??? Anyone know how to fix this?

The key cylinder in the steering column isn't the actual switch, it's only a key cylinder. The switch itself is farther down near the base of the steering column and the key cylinder is connected to it by an operating rod.

Check to see if the rod is adjusted correctly and putting the switch in the OFF position when the key is in the OFF position. Then check the switch itself to see if it may be self-destructing.

Check the fuel pump relay.

Thanks for the leads.

Eagle said:

The key cylinder in the steering column isn't the actual switch, it's only a key cylinder. The switch itself is farther down near the base of the steering column and the key cylinder is connected to it by an operating rod.

Check to see if the rod is adjusted correctly and putting the switch in the OFF position when the key is in the OFF position. Then check the switch itself to see if it may be self-destructing.

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Looks like you may have the right idea; if I'm looking at it correctly the rod you're talking about is on the passenger side of the column??? Mine dosn't move, what is it supposed to do? Thanks again.

slowrider said:

Looks like you may have the right idea; if I'm looking at it correctly the rod you're talking about is on the passenger side of the column??? Mine dosn't move, what is it supposed to do? Thanks again.

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no it's on the drivers side of the column (the ignition rod) and when you turn the key it pulls this rod toward the driver and by doing that it turns the ignition switch through the acc off on start positions. :wave:

You don't have the battery connected backwards do you?

Don't think leaving the ignition key in the "on" position will result in the fuel pump running continously. As I recal, the pump will come on for about 2 sec when the key is first turned on, then go off unless you are either cranking or the engine is running. This is because the ECM controls the pump via the fuel pump relay. So a failed ignition sw won't cause your problem; however, as I recall, the ignition sw places Batt (12V) on all of the relays' control windings, then the ECM places a ground on the selected relay, such as the fuel pump, O2 heater, Etc., causing it to energise. On the '88 Cherokee, Batt is always on one side of the fuel pump relay--ign key has no affect on this! My bet is on a fuel pump relay that is stuck in the "on" position. Pull the relay and see what happens.