Fuel Pump

[Anak]

from FSM 96.
6 cavities
#1-relay output(power?) DG/rd tracer
#2-sensor ground Bk/Lb
#3-Fuel level sensor DB
#4 open
#5-low fuel sensor Db/wt
#6-Ground BK
plug
6-5-4
3-2-1

Good info Wayne.

Copied and pasted into my thread on the '96 fuel system.

 

[BrokenSockets]

OK, testing 1 to 6 for 12 volts.

Fuel filter is not too old, but even if it is totally clogged I think it would just keep the engine from running rather than having no pump priming whine.

 

[BrokenSockets]

I can run the pump from a 12 volt battery from the pump assembly pigtail with pins 1-6. I measure 12.5 volts between pins 1 and 6 on the harness connector from the front at prime and while cranking. Plug them together - no pumping, no pump noise.

I am going to try to jumper over the connector.

 

[Anak]

That is an interesting situation.

It is hard to imagine the pins inside the connector went bad, especially while plugged in, but I suppose given enough time and vibration it could happen.

A jumper sounds like a reasonable way to test that theory.

If that doesn't pan out I would then wonder about the quality of an upstream connection. The reading on a multimeter may not be the same as what you get with the load of the fuel pump. The fuel pump relay and the chassis ground would be my next two suspects.

 

[Runnin'OnEmpty]

If that doesn't pan out I would then wonder about the quality of an upstream connection. The reading on a multimeter may not be the same as what you get with the load of the fuel pump. The fuel pump relay and the chassis ground would be my next two suspects.

What Anak says here is absolutely true. If the circuit is marginal, a voltmeter
will show the full potential. When a load is placed on the circuit, the high
resistance will prevent the load/fuel pump from running.

Not adding anything new here, just reinforcing what Anak said. I've run into
this before when chasing electrical gremlins. I agree with the pump relay or
ground being the problem, as well as perhaps the relay socket.

 

[BrokenSockets]

Hey guys - I took measurements with a pin probe with socket connected. At the Fuel pump assembly, I got less than 8 volts and it dropped quickly with key on. Then jumpered around the big connector on pins 1 and 6 and everything is good. 12 volts or more all the way to the pump and the jeep is running. Connector pins looked ok when I opened it up - must be a bad connection inside the sockets. I did both 1 and 6 for the hell of it - could have been either one that was bad I guess.

I could replace the connector, but shrink wrap and tape was cheaper (and I had it handy.) Permanent fix as far as I am concerned.