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post #1 of 22 (permalink) Old 02-03-2008, 05:38 PM Thread Starter
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Question 94 thunderbird 4.6 wont start

like the title says it wont start, last week I was driving it home and all of a sudden the car cut off for a second then about 5 mins later it did it again I was driving about 65 mph I got off the freeway and it was fine for about 10 mins then it cut off again it progressively got worse eventually it stalled out, it would start for a minute then quit again so I towed it home. Saturday it started and ran for about 15 mins then it started cutting off again and it would start and run for a second so I figured it was something over heating on it so I decided to wait till today to play with it, well this morning it would only start and quit after a second so I pushed it into the garage and this is what I've done so far I wiggled the crankshaft sensor plug, unplugged MAF, checked and cleaned the ground wires, made sure everything was plugged in. I pulled the codes it says passed I figured that because no CEL. I checked the fuel pressure when you turn the key on it shoots up to 38 - 40 but it leaks down fast, if you leave the key on without turning it over the fuel pump and the ccrm keep coming on and off. with the leak down I was suspecting fuel problems so I poured some gas down the throttle body and it started up I left the fuel pressure gauge on and it would shoot up to 40 and back down, up to 40 and back down when the car was running it was surging when it did this it only ran for maybe 30 seconds, I could hear the ccrm making noise (clicking) but I really couldn't here the fuel pump. Any ideas? I hope its not the fuel pump I really dont feel like changing it, 2 weeks ago I just put the trans back in and I still have to put in the new rack, I dread crawling back underneath it.
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post #2 of 22 (permalink) Old 02-03-2008, 08:38 PM
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Have you changed the fuel filter lately? Maybe it's clogging. Either that or the fuel pressure regualtor is going bad.

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post #3 of 22 (permalink) Old 02-04-2008, 09:31 AM
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Did you try and start it with the MAf unplugged or just checked the connection?

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post #4 of 22 (permalink) Old 02-04-2008, 10:16 AM Thread Starter
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fuel filter is good and I tried starting it with the MAF unpluged no difference I just got home so I'm going to play with some more today.
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post #5 of 22 (permalink) Old 02-04-2008, 11:18 AM
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Fuel pump Relay maybe?
On my old truck I had this same problem.After much aggravation I replaced the fuel pump Relay(Circuit opeing relay) and the problem went away.Check the Relay.

04 PI swap,SVO Supercharger 8-9 psi,Alcohol injection,39lbs Cobra injectors,XCal2-Walbro 255 LPH fuel pump,4.10 T-Lok,2003 4R70W built to withstand by RobertP,450hp JMOD,3800 circleD stall,trucool 4739 Trans Cooler,Dynotech 3.5 Driveshaft,70mm T/B,SCP Cold Air Intake,90mm LMAF,JBA headers,Magnaflow Midmount,No cats with 3inch piping,Vogtland 1.6inch drop,Cobra R's and xenon body kit.

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post #6 of 22 (permalink) Old 02-04-2008, 02:56 PM Thread Starter
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it doesn't have a single f/p relay it's in a box with all the relays, which I think is my problem,
I have 2 questions 1 is when I turn my ignition key on I hear the pump kick on for about 1-2 seconds and if I leave the ignition on with out starting I can hear the ccrm clicking the pump on every few seconds sometimes 3 or 4 times in less than 20 seconds or not at all for over a minute 2. while cranking the car over should the fuel pump kick on? any help
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post #7 of 22 (permalink) Old 02-04-2008, 04:00 PM
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do 97 have ecu fuel pressure sensors?

I know 94-95's dont... but 96-97 were full OBDII compliant.

If the ecu is seeing a pressure drop in the system when the key is turned to on but not started it will keep priming as needed to keep pressure up. (if it has a ecu fuel pressure sensor) then the question would be, where is the fuel going? bleeding back through a bad fuel pump? stuck injector? Ecm hanging and injector open (had this happen to me maybe 2 years ago).

Bottom line it sounds like fuel starvation. Start from one end and work your way forward eliminating any possibilities along the way. fuel pump, fuel filter, fuel rail, fuel regulator, injectors, (and injector pulse, make sure its not being instructed to stay open) and finally the obvious .... leaks.

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post #8 of 22 (permalink) Old 02-04-2008, 04:08 PM Thread Starter
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I think it's the ecu because when I'm sitting in the car and the fuel pumps keeps kicking on the CEL goes off but comes back on when the pumps shuts off, the pump kept kicking on and off real fast for about 10 seconds when it did this I tried to start it and it ran for about 5 seconds reving up and down. is their a sensor that tells the relay to turn on the pump?
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post #9 of 22 (permalink) Old 02-04-2008, 04:13 PM
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That would be the question, I dont know for sure if 96+ mn12's have ecu fuel pressure or not. But from what you just posted, sounds to me to be electrical. You said you had the tranny out already... you might have a short in the wiring?

Although that is curious what the CEL light is doing...

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post #10 of 22 (permalink) Old 02-04-2008, 04:27 PM Thread Starter
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the problem is on my 94 bird, not the 97 cougar, I thought about the wiring and I checked everything that I can think of, I thought about swapping the ecu from my cougar to the tbird to test, same engine but 3 yrs difference would they be the same?
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post #11 of 22 (permalink) Old 02-04-2008, 04:30 PM
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When you pulled the tranny I assume you droped the tank.Is it a possibilty that somthing is hanging loose?Like the connecter for the pump?Did you use Dielectric grease when you put it back in?

04 PI swap,SVO Supercharger 8-9 psi,Alcohol injection,39lbs Cobra injectors,XCal2-Walbro 255 LPH fuel pump,4.10 T-Lok,2003 4R70W built to withstand by RobertP,450hp JMOD,3800 circleD stall,trucool 4739 Trans Cooler,Dynotech 3.5 Driveshaft,70mm T/B,SCP Cold Air Intake,90mm LMAF,JBA headers,Magnaflow Midmount,No cats with 3inch piping,Vogtland 1.6inch drop,Cobra R's and xenon body kit.

Its slow, Really.
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post #12 of 22 (permalink) Old 02-04-2008, 04:32 PM Thread Starter
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and it's still not showing any codes
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post #13 of 22 (permalink) Old 02-04-2008, 04:38 PM Thread Starter
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I plugged everything back in, I didn't put any grease into the plug it still had grease and it wasn't dried up. I don't think it's a short in the back because I can hear the relay in the ccrm clicking every time the pumps kicks on.
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post #14 of 22 (permalink) Old 02-04-2008, 06:54 PM
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MN12s don't have fuel pressure sensors.

And a 94 PCM will not work in a 97 car and vice versa.

And a short in the wiring would almost always blow a fuse if its fed from the PCM, which the transmission harness wires are.

The behavior of the CEL and fuel pump almost sounds normal. When the key is turned to START, the CEL goes out and the fuel pump comes on. You didn't say if you were moving the key or not, but if you aren't it almost sounds as if the ignition switch is faulty. The PCM directly controls the relay for the fuel pump based on ignition switch position and whether or not the car is running, so if the switch is screwed up, it could be making the PCM cylce the relay rapidly as you described.

My advice is to take off the steering column trim and remove the ignition switch (held by 2 torx screws) leaving it plugged in. Then manually move the lever of the switch and see if it changes anything. If it acts differently or normally, you've found the problem.

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post #15 of 22 (permalink) Old 02-04-2008, 07:25 PM Thread Starter
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when I turn the key on the pump will come on if I leave the key in the on position the fuel pump will cycle on and off and the cel will go and on and off intermittently without touching anything, but when I turn the key to the start position the fuel pump will not turn on. the car will start for a second from the initial fuel, but the pump is not coming on to keep the fuel coming. does it have a second relay that tells the pump to stay on possibly? could I run a jumper wire directly to the pump and make it stay on?
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post #16 of 22 (permalink) Old 02-04-2008, 07:31 PM
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You could run a wire to the Light Blue w/Orange stripe wire going to the CCRM and you can directly control the relay and fuel pump that way. There is only 1 relay for the pump and it's in the CCRM, controlled directly by the PCM.

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post #17 of 22 (permalink) Old 02-04-2008, 07:54 PM Thread Starter
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ok I ran the jumper wire the fuel pump comes on but when I went to turn the key on it stopped pumping when I shut the key off it started pumping again? when you turn the key to start it still wouldn't pump? doesn't make any sense?
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post #18 of 22 (permalink) Old 02-07-2008, 10:47 AM Thread Starter
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Well I've come to the conclusion it has to be the computer, my question is will a computer from any 94 work because when I check car-part.com it shows 3 different id's and of coarse the one that matches mine I would have to drive 135 miles to get it.
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post #19 of 22 (permalink) Old 02-07-2008, 12:19 PM
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Nope. You need a 97 w/ the same catch code IIRC.

Jay

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post #20 of 22 (permalink) Old 02-07-2008, 12:34 PM Thread Starter
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this for my 94 tbird, you mean I have to have the same code for a 94?
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post #21 of 22 (permalink) Old 02-07-2008, 02:40 PM
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Yes it's best to stay with the same catch code.

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post #22 of 22 (permalink) Old 02-09-2008, 09:52 PM Thread Starter
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Just wanted to let everyone know that it was the computer, I put a new one in today and it started right up! thanks for the help!
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