Little Help with Fuel pump

[bbbngowc]

Hi Guys,

I'm a noob at this whole mechanic hobby, but I do like to diy and I have a 1991 Mustang GT Hatch to play with.

Car has been sitting up from August. Not driving or starting at all. The other day I put in a battery and go to start it up but I did not hear the fuel pump prime. Of course it did not start (just kept rolling over and over). So I was wondering what do I check first? I've read a few posts but they have me completely lost. So I just need a step by step on what to do in laymans term.

I read a thread about checking the relay.

Where is the relay in this car? Under the drivers seat or in the engine bay on the passenger side?

C'mon guys ... help ma ... step 1?

 

[liljoe07]

Look under the drivers seat. Id pull the seat as it makes it easier to test the relay.

Turn the key on and check the voltages on each of the wires. Post up the voltages you get for each colored wire.

 

[BYRDPE]

i have a 92 and my relay is located under the maf meter under the hood.

 

[liljoe07]

i have a 92 and my relay is located under the maf meter under the hood.

His is a 91.

 

[bbbngowc]

Ok, I took a pic of the only wires under my seat. I should also mention that the previous owner installed a fuel pump kill switch. I know that adds to the troubleshooting.

 

[BYRDPE]

Ok, I took a pic of the only wires under my seat. I should also mention that the previous owner installed a fuel pump kill switch. I know that adds to the troubleshooting.

that looks like the relay.

 

[bbbngowc]

How do I test it?

 

[bbbngowc]

How do I test it?

I placed a test light to it and I'm getting voltage to all wires except the green one. I assume the green is ground.

 

[bbbngowc]

There's a relay under the MAF on the passengers side that clicks whenever I turn the ignition on/off. Could that be the issue, or is it suppose to do that?

 

[HISSIN50]

There's a relay under the MAF on the passengers side that clicks whenever I turn the ignition on/off. Could that be the issue, or is it suppose to do that?

If the car won't start:

Check your TPS reading key-on with the engine off. Because of your observation, the TPS might have a short and the EEC thinks you're at WOT (that's your WOT relay clicking. The EEC energizes it at the EEC's definition of WOT, per the TPS).

This will keep injectors from firing and the car won't start.

 

[bbbngowc]

If the car won't start:

Check your TPS reading key-on with the engine off. Because of your observation, the TPS might have a short and the EEC thinks you're at WOT (that's your WOT relay clicking. The EEC energizes it at the EEC's definition of WOT, per the TPS).

This will keep injectors from firing and the car won't start.

Ok TPS is the throttle positioning sensor right?

How do I check it?

 

[liljoe07]

With a volt meter.

Key on use the Green and Black TPS wires to get the reading.

Either way you should here the pump prime once the key is cycled on. Have you check the inertia switch in the trunk? Make sure its pushed down.

 

[bbbngowc]

With a volt meter.

Key on use the Green and Black TPS wires to get the reading.

Either way you should here the pump prime once the key is cycled on. Have you check the inertia switch in the trunk? Make sure its pushed down.

How will I hear the pump prime if that's what I'm troubleshooting?

Where is the inertia switch?

 

[liljoe07]

What I meant was, that even if the TPS voltage is too high, the pump will still prime.

Forget everything..... You said you have voltage at all the wires but the dark green wire. Thats the wire that goes to the pump. so when the relay engages that wire should be hot.
Use the diagram below and run a jumper wire from the Fuel pump trigger to a ground. Turn the key on and see if the pump primes.
View attachment 236617

The connector above is located behind the driver side strut tower.

Inertia switch is located in the trunk, mounted on the trunk frame right behind the driverside tail light.

 

[bbbngowc]

I tried to what you suggested with the diagram, but the pump still didn't prime.

I took a wire and connected it to the negative battery terminal and then stuck the other end in the fuel pump trigger. Did I do that right?

 

[liljoe07]

Remove the fuel pump relay, use a jumper wire and go from the Pink/ black wire to the Dark green wire. Pump should come on. If it does, then replace the relay. If it doesnt, then the problem is else where.

 

[bbbngowc]

Will try that and let you know.

 

[bbbngowc]

Remove the fuel pump relay, use a jumper wire and go from the Pink/ black wire to the Dark green wire. Pump should come on. If it does, then replace the relay. If it doesnt, then the problem is else where.

Oh man. This worked. I jumped the wires and the pump came right on. sweet! So I'm going to pick up a new relay today.

Do you suppose the relay went bad from natural wear/tear or there is an electrical issue that should probably be investigated?

 

[liljoe07]

Oh man. This worked. I jumped the wires and the pump came right on. sweet! So I'm going to pick up a new relay today.

Do you suppose the relay went bad from natural wear/tear or there is an electrical issue that should probably be investigated?

Just to make sure its not ECM related. Test the pink/black wire and the Red wire. Bothe should have voltage with the key on. If thats good, the use the test light or meter and go from the Pink/black wire to the orange/light blue wire. Turn key, test light or meter should register 12v or so for a short time, then go off. That would be the ECM controlling the ground properly, and everything is fine there. IF all that checks out. just replace the relay.