1993 Mustang Cobra Fuel Pump Issues

Sep 21, 2016
First I want to thank jrichker for his in depth post about the fuel system and electrical diagnosis which has got me almost to beat this issue.


Now to what I have. My dad owns a 1993 cobra and bought it brand new in 93. He has an issue where the fuel pump stopped working. I read the above post and tested all the above. relay is good, inertia switch is good, and fues links are good. My problem is that when I turn the key to run, the fuel pump does not turn on and the relay does not click. I hook up a jumper from the ecc test connector pin to ground and the relay clicks and the pump turns on and does not turn off, just keeps running. Even if i remove the jumper wire from ground, it just continues to run. So I test this section of jrichkers post ("The light blue/orange wire provides a ground path for the relay power. With the test connector jumpered according to the previous instructions, there should be less than .75 volts.") When I do this, I get around 8 volts instead of .75 volts. Which tells me that maybe I have two wires that have maybe been ate up by mice and got crossed with each other. So I cut the light blue/orange wire, solder on a long wire that I run right to a chassis ground. Now I turn the key to run and the fuel pump turns right on but does not shut off. So im then led to believe that maybe no wires are crossed but instead the ecc computer has gone bad.

I get the part number off the computer and it is the X3Z computer. I look around and they are about 400 bucks for a new one. But I can find used ones on ebay that are the A9L and A9P. And they are a dime a dozen. Im curious if I can change out the x3z computer with one of the others and even if I have a slight drop in car performance, that is fine, dad just putts around in it anyhow and doesnt have hardly any money to throw at it (kind of why im the one trying to fix it) Any help or suggestions would be awesome and Thanks again to jrichker and this forum for the awesome help so far..


I didn't really have an issue with the stink...
SN Certified Technician
Mar 2, 2015
You can send the computer out to be repaired. Is it stick or auto ?


Car used in adult film "Highway Gangbang-InDaButt"
SN Certified Technician
Feb 18, 2001
If you change to the A9L computer, you will need to change the injectors to 19# and change the MAF to a standard 5.0 Mustang MAF to get it running correctly.

To retain the stock 24# injectors and MAF, you'll need a tune.

Might be cheaper/easier to repair the X3Z
Sep 21, 2016
I see. Anyone have a guy who they trust to work on these and any idea what the cost is. Or if someone has one laying around that they want to sell?


I plan to eventually problem is time
Mod Dude
Apr 6, 2011
Hillsborough county
I believe in the MAF uses the stock curve all the extra fueling is done in the ECU. Have you check to see if the computer pulls it to ground when you turn on the key maybe try grabbing the wire for the fuel pump off the ECU and tying it directly to the relay you may have a break somewhere in The Wire just a thought. If you do get a9l you will need to get the matching 19 pound orange top injectors from a Mustang or Explorer
Sep 21, 2016
I wanted to give an up date on the situation with the car. I hate when people figure out what was wrong but never update the thread with the answer. So just to recap. I Turn the key on and the fuel pump does not prime. I use the jumper wire at the test port and the fuel pump kicks on but does not turn off. I run through all the test as described in the above thread by jrichker. I pull the ECM (COMPUTER) and once I get down to the board (which is the first picture) I see that two of the blue barrel looking things (capacitors) are burned up. (second picture has a close up of one of the capacitors) I buy three of them off ebay (two of them are 47uF 16V capacitors and one is a 10 uF 35V capacitor) I solder them on to the board and now my dads 93 runs again. Just want to say thanks again to everyone who continues to contribute to these forums.