Fuel pump won't come on.

[poppy1440]

Hello,
I was checking my fuel pump wires at the rear of the car trying to figure out how to install my Hobbs switch. I had the car running. I was using a light tester and when I probed the grey wire in the picture. The car killed and won't crank now. I checked the fuel pump fuse and its good.
If I put voltage on the grey wire at the hot wire relay the relay turns the fuel pump on. So i know that the fuel pump and relay are working.

I checked the relay on the passenger fender and I only get voltage on one wire even during the cranking cycle.

While checking out the relay i notice a wire in the area that looks like it might belong in the fuel pump relay harness.

The harness has 4 wires connected now, could someone please check there car and see if there are suppose to be 5 wires.

Any help would be appreciated,
Thanks

 

[poppy1440]

Trying to upload pictures
Having trouble right now

 

[poppy1440]

Pics

 

[Gene Van Horn]

Dude that thing is ugly, need to cut that plug get a new one, possibly from caspers. Im sure that wire goes in there somewhere also. Maybe get a hot wire kit while your at it.

 

[bpman1234]

Is that the bottom of your relay? If so i would really clean that up get a caspers harness side relay adapter replacement .and new relay .then see what happens

 

[poppy1440]

Yes that is the bottom the relay.
I already have a hot wire kit on it.

Im just puzzled at how could I possibly have burnt that wire just by probing the signal wire on my hot wire kit

 

[Gene Van Horn]

You must have just shorted it out is all

 

[poppy1440]

Is this what I need.

I hope that they are open tomorrow i am trying to get the car ready to go out of town next weekend

 

[poppy1440]

The Casper's harness only looks like it has four wires. Can someone please look at their harness and see if it has 4 wires or 5

 

[TurboBuRick]

There is only 4 wires.

Check inj/fuel pump fuse in the fuse panel.

There are 2 relays on passenger fender. The one with the grey plug is the fp relay. The black plug one is A/C.

 

[haywire4130]

The ecm sends power to close the relay on the fender for x seconds when you first key the ignition to run (prime), and resumes after the car is started. Have an assistant key it on and off while you check it with a test light, if youre doing it by yourself you wont make out to check it unless watching through the windshield with the test light clipped on. Just a background so you dont condemn good parts or chase your tail.

 

[Buckshot G/N]

Four wires it all the harness should have, that system you have my friend looks awfully rough, a good cleaning may help ,but I think you just aggravated something that was about to deteriorate shortly . Call caspers and do it right.

 

[poppy1440]

The harness in picture is actually for the AC the one for the fuel pump relay actually looks pretty good.

I ordered a fuel pump relay this morning but I don't think that the relay is the problem I think I have a short on the signal wire that turns the fuel pump on because at the fp relay harness i have 12volts on one wire at the bottom with the key on and 12 volts on the wire above it for 2-3 sec when the key is first turned on like it should. The wire on the other end of the harness is a ground. If I am thinking correctly if I wanted to bypass the relay for trouble shooting purposes i would only need to supply 12volts to the hot wire, prime wire and grey pump turn on wire and I should hear the pump come on correct.

I ohmed the ground wire and the grey wire and it didn't ohm out so I don't think I have a direct short but if I use a volt meter i get 7.5 volts on the grey wire.

I have verified that the fuses are good in the fuse box and the hotwire kit and I used a known good relay in the hotwire kit and I bypassed the hotwire kit as a check.

I think the grey wire is broken my next test is to ohm the grey wire at the fp and up front.

I have verified that the pump come on if I ad 12volts to the grey wire at the rear of the car just nothing if I supply 12 volts at the grey wire in the front

 

[poppy1440]

Any ideas

 

[poppy1440]

I don't think I should have 7.5 volts on the trigger wire

 

[TurboBuRick]

Check for power at the connector in the trunk on the driver side. It's tucked down in the quarter panel. All the wires for the fuel pump run through that connector. Maybe there is a loose or corroded wire.

 

[RmvBfrFlght]

I have verified that the pump come on if I ad 12volts to the grey wire at the rear of the car just nothing if I supply 12 volts at the grey wire in the front

There are multiple connectors involved in getting the FP power from under the hood back to the fuel tank. Starting under the hood the gray wire goes to the main bulkhead connector (C100, cavity G6).

Now in the interior there is a small vertical connector on the left side of the fuse block (C209, location K). It is a dark brown or copper colored wire. This wiring runs under the door sill plate to the trunk.

Once in the trunk there is another connector (C320, location G). This is the one Rick is referring to.

From there the FP power runs to the 3-wire connector for the sending unit.

RemoveBeforeFlight

 

[poppy1440]

I have narrowed it down to a broken grey wire i just don't know where yet.

The grey wire at the relay and the grey wire fuel pump test wire both have voltage for a few with the key on.

If I run a jumper from the grey wire up front to the grey wire at the fuel pump in the rear the pump will come and prime as it should.

If I can't find the break and I have to run a new trigger wire to the rear harness should I tie it in at the relay or can I just use the fp test wire?

 

[poppy1440]

Thanks fellas, the harness in the trunk was the problem.
I had to jumper a wire around the harness because although I cleaned the contacts good it was still hit and miss on continuity so I ran a jumper wire for safety.

Thanks again

 

[Gene Van Horn]

That good you got it running, now get that hot wire hooked up the correct way and you be in bussiness.