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1986 Mustang GT wont keep running

879 Views 5 Replies 4 Participants Last post by  89coupe, 
W
Hello, I have a 86 GT Just rebuilt the car completely. Problem is it intermitanly will not run. Friday it was fine today it will crank and sometimes will start and run for a second or 2 but then dies. This is just a recent thing. I had no problems with it after putting it back together, putting the engine in - all fine. I drove it home with no problem. Took it to get an alignment and the guys there could not start it. Then I could not start it. Towed it home. Let it sit for a week, it fired right up. I changed the Ignition module - the one on the distributor. Drove the car aroud the block a few times a few different occasions - no problem. Took the car to get an alignment again - it ran fine till they went to take it off the rack - no good - pushed it off the rack and out side - started right up. Drove it home - no problem. Today no good. It will crank - i have 40+ psi of fuel pressure - it will start and run for 1 or 2 seconds then dies, just as if you turned the key off. With the exception of the computer and dist. and switch all ignition parts are new. Any ideas. Thank you
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ttopstang
it might be the distributor. the tfi module on the side.

also the fuel pump. fuel pumps act up a bit, and when they get hot and you turn the car off, they dont want to come back on.
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could even be a faulty battery. my car was doing that...it would start and run fine then when i turned it off and tried to start it again it wouldnt. one night i was out with some friends and it wouldnt start so i called a tow truck and they couldnt start it and when we got to my house it started right up. i would have your battery checked but dont go to a regular auto parts store. i went to pep boys to have it checked and they said it was fine but when i took it to sears where i bought it they said it was dead. i found out this was because pep boys didnt put it under a load they just checked for voltage. but i hope you figure it out!:bigthumbsup
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W
I did change the TFI modual and the battery is a new optima red top. I did relocate it to the trunk, but it seems good. I am going to do some ignition checks tonight. I got home last night and it will only crank now. Does not even run for the few seconds. So hopefully what ever was going bad is now just bad. That makes finding the problem a lot easier.
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W
I think I got it. Did some test last night. The coil does not send out a spark. Checked the TFI and the harness at pins 3 & 4 should have at least 90% battery voltage in start or run depending on the pin. Pin 3 had 11.7 volts in start and run but pin 4 only had .5 in run. So it looks to be a bad ignition switch. $12.49 from O'Reilly's. I will change that tonight or tomorrow and well see if she starts. :scratchchin
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89coupe
PIN 3 should be hot in Run only, and 4 should have constant power.
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