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Discussion Starter · #1 ·
Greetings All...

Been many, many years since I visited any of the 'Stang Forums out here (mostly because I've just been driving my GT and enjoying every trouble-free minute of it) but have found myself perplexed by it's current state...

Went out to start it up and drive to work: KO, fuel pump spun up, cranked it, caught (all normal to this point), then died. KO=no fuel pump spin, cranks fine, no start. No Check Engine Light.

Hooked up the scanner and stared in disbelief as the codes started flowing:

21,24,67,95... WTF???:eek:

Anybody see a common failure point that would throw all of those on a previously clean scan?????? Has to be electrical and has to be a fuse, relay, or fuseable link somewhere... I've checked the fuse box and all is well, but didn't really think I would find the answer there...

HELP!!!!!!!!!

DS
1991 GT T5
 

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so your saying the fuel pump didnt come on the second time.???????it may be the relay under the seat
 

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Discussion Starter · #4 · (Edited)
so your saying the fuel pump didnt come on the second time.???????it may be the relay under the seat
Correct...

Diagnostic Trouble Codes
here you can find what the codes are
Sorry, should have mentioned that I know what the codes mean, just can't figure out what would cause them all to post in one shot...

21:ECT out of range
24:ACT out of range
67:Clutch Switch, Manual Lever Position Switch, Air Conditioner Clutch
95:Fuel Pump Monitor - problem with circut

I have checked the inertia switch (good)
Will go looking for problems in this order:

Jumper to fuel pump to verify function independent of FPM
Realy under driver's seat
Fuseable links @ starter relay

Other suggestions? I have 24 hours to figure this out... :(

Should also mention that the car ran/drove fine the night before...

\m/ DS
 

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Sounds like you are having computer problems. It is unlikely that all of these things went wrong at the same time and the only common circuit they share is the computer (the fuel pump relay circuit is grounded by the computer when it gets a signal from the TFI).

My guess would be either a bad ground at the computer or it is time to get a replacement computer from autozone.
 

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Discussion Starter · #7 ·
OK, here is the latest.....

I have power at the fuel pump relay and here it click closed @ KO.

Have been unsuccesful in forcing a fuel pump spin @ EEC connector.

I am alone, so have not been able to check for prime signal @ fuel pump harness at the tank @ KO.

Which of the four pins would I energize @ the fuel pump harness to power the pump?

I am down to pulling the pump or replacing the computer... I want to make damn sure it is or isnt the pump before yanking the tank or replacing the computer..

Too bad it is not nice enough weather to ride my VMax... :(

HELP!!!!!! :eek: (With the car, not the weather...)

\m/ DS
 

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Discussion Starter · #8 ·
In addition, the following pins on the ECM harness (computer disconected) have power at KO:

1
12
13
14
15
21
37
42
52
57
58
59

No other pins show power...

Helpful?????
 

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you can pull the fuel pump relay and jump it out you will here the pump or you can also put a fuel pressure gauge on the car and see if you have fuel pressure
 

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Discussion Starter · #10 ·
Sorry, should have mentioned that I had jumped the relay already... No dice...

Now I have replaced the computer... Still no dice...

Throwing the exact same codes as the old one..

Done for the night and now trying to find a ride to work in the morning... :(

How can I force a spin on the pump (or try to) before I drop the tank and replace the damn thing?

...and should I REALLY be looking at a fuel pump, ECT, and ACT as well?

I'm too old for this ****... Anyone want a '91 GT CHEAP... :eek:
 

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Your pump is bad. If it doesn't spin by jumping the relay and you have power at the relay, the pump or the wiring behind the relay is bad.
 

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Discussion Starter · #12 ·
Waht about the ECT and ACT codes that showed up at the same time?

Coincidence? Wouldn't suprise me at this point... :no
 

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Strange, but it may have something to do with the failed fuel pump acting as a ground.
 

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the computer can not tell if the fuel pump failed so when there is no fuel the car will not run and set off codes because it can not start and run change out your pump and run the car, clear all codes then recheck if they came back you have to fix one problem at a time
 

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Discussion Starter · #15 ·
...And The Winner Is

T'was the fuel pump...

After wrestling the full tank out of the car and changing the pump (and then getting it BACK into the car), my GT roared back to life...

Incidentally, still threw ECT and ACT codes, so changed those as well...

Code free and back on the road... Just in time to get my VMax wheels down to the local Yamaha shop for some new rubber... :D

Thanks to all who contributed to the revival.:yes

\m/ DS
 

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gees.....you must have cranked out a nice little chunk of change.......but it does go to show if you replace enough parts it will be fixed eventually
 
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