New member with a just purchased 1991 LX convertible.
- Thread starter Libby24
- Start date
Fuel pump relay is under the driver seat. Use this wiring diagram:
You can test the fuel pump with the ignition key in the run position and apply a ground to the dark green/yellow wire in the diagnostic connector.
If the fuel pump comes on then you know that it is good. The next step would be to pull codes from the ECU and remember that the check engine light (CEL) only comes on for emissions related codes. There can be other codes present and the CEL will never illuminate or flash. If you cannot pull any codes chances are the ECU is bad and needs repair.
You can test the fuel pump with the ignition key in the run position and apply a ground to the dark green/yellow wire in the diagnostic connector.
If the fuel pump comes on then you know that it is good. The next step would be to pull codes from the ECU and remember that the check engine light (CEL) only comes on for emissions related codes. There can be other codes present and the CEL will never illuminate or flash. If you cannot pull any codes chances are the ECU is bad and needs repair.
Hey Thanks! I have seen these before but as I said my wires are a different colors for the most part. Also I only found a capped wire lead under the seat, I did find a relay in the drivers side kick plate, where I did read it might be located. I cleaned the wires as they were quite corroded and got a new relay. I tried the jumper wire test and had no luck. I'm going to go back and retest the wires at the relay, with the relay disconnected and connected, as well as directly trying to power the pump to confirm it works. (was told it was replaced 1 year ago).
So someone has hacked the wiring up on the car. I have never seen the fuel pump relay anywhere but under the driver seat and then in mid 92 they moved them to in front of the passenger shock tower under the hood.
So I rechecked and the connector under the seat has all the correct wire colors so I put my new relay there. nothing has changed . I just ordered another relay to fill the spot I had before by the kick plate, b/c why not? both of these locations look all factory. BUT somewhere along the line there was an aftermarket command start added, so wiring is not virgin for sure. My buddy told me to remove it all but I want to hold off on that as if I just spray some fuel in the throttle body it will fire and run. I just can't get more than 7 and 8 volts back at the fuel pump connector ( 2 diff. pins) by the tank. I tried to send 12 volts from a battery to the pump and it did not run. I'm guessing it should be a full 12 volts there. Can I run a wire back to the pump for 12 volts key on? I should add that someone bypassed the Inertia switch and just crossed the wires, I'm not sure if that matters as it is a NC switch.
I would print out the two images above, get out my trusty Multi-meter, identify end-to-end the wire colors that you [do] have and re-label the diagrams accordingly. Ultimately, your wiring should mimic the diagrams above regardless of the wire colors.
You can even run new wire if you prefer, and strip the others out when you're done and certain that your circuit is good.
I had some similar issues on an 89 I used to own.
If it's a car that you plan to keep, put in the effort to make it right. That doesn't mean you need to follow a specific diagram however, [your] set of diagrams that you make as you go, should be accurate.
You can even run new wire if you prefer, and strip the others out when you're done and certain that your circuit is good.
I had some similar issues on an 89 I used to own.
If it's a car that you plan to keep, put in the effort to make it right. That doesn't mean you need to follow a specific diagram however, [your] set of diagrams that you make as you go, should be accurate.
The inertia switch bypass is a hint to more issues that the PO didn't/couldn't fix, I wouldn't run without a functioning inertia switch.
There is s connector in the driver side kick panel that the fuel pump wring passes through. You need to chase the power wire from the relay all the way back to the pump. Use a DVM like Noobz mentions and set it to continuity so that when you touch the two probes together it beeps. This will allow you to make sure the wire from the relay back to the pump is good. You will need to check the connector in the driver kick panel to make sure that connection is good. If the previous owner hacked this up then fix it.
Get the inertia switch wired back in and test the switch to make sure it works. This thread has a couple of ways to test it:
This thread has some pictures of the wiring behind the driver side kick panel of a 1991 Mustang:
Here is the full ECU wiring diagram for your car as it may help down the road:
Get the inertia switch wired back in and test the switch to make sure it works. This thread has a couple of ways to test it:
This thread has some pictures of the wiring behind the driver side kick panel of a 1991 Mustang:
Here is the full ECU wiring diagram for your car as it may help down the road:
Update. ! I got it running! I changed the relay in drivers kick panel, and put one in the harness under the drivers seat. (there wasn't one plugged in there. New fuel pump. But what I found was when I tried to use the diagnostic port I moved some wires and the fan & pump started. I found a bad wire (repair) at the end of a fuseable link, repaired it and now runs great! Thanks for all the help and the wiring diagrams! I really appreciate it! Now to find me a V8!
Ok Guys new question, does anyone have advise or has done a 5.0 HO. swap from a '92 Cougar into a '91 mustang with a 2.3 ltr. 4cyl.? What are the chances the 4 speed OD trans will fit as well? I'm guessing that I will need a different Rear axle and a different drive shaft, does anyone know of any parts that would swap over or be relatively easy to modify to work? Any tips would be appreciated
Nope. None of the 83-88 T-Bird or Cougar motors were High Output or HO. They were standard output or SO. The firing order is non-HO so it’s the old 289 / 302 firing order.
Yes the AOD transmission will fit.
Yes the AOD transmission will fit.
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Okay, so I completely missed this was coming out of a 92 cougar which is a totally different platform than a Fox. It is called an MN12 which I also owned at one point. The transmission is still an AOD so you are good to go there however I believe the shift linkage on it is different than what you will need for a Fox so you will need to do some research there. The rear end in the 92 is an IRS (at least I think it is) so that would take some work to get into a Fox. Most use the IRS out of the 99-04 Cobras of which I helped on an install and it was not bad but my buddy bought an install kit which helped a lot. I am pretty sure the mounting locations on the Thunderbird and Cougars are different vs the 99-04 Cobras.
I will say that a 7.5 rear end will hold a bit of hp so you could transplant the motor and transmission out of the donor car and drive it as is for a long time with the 7.5 rear end.
I will say that a 7.5 rear end will hold a bit of hp so you could transplant the motor and transmission out of the donor car and drive it as is for a long time with the 7.5 rear end.
On the shift lever thing, if the cougar is a column shift the trans lever needs to be dealt with, you may be able to flip it but not sure, if the cougar is floor shift then it will likely work, the cables may be different you'll have to compare.
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