Dead Battery = Bad Sensors???

dwleo

New Member
Jan 21, 2002
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Vancouver, BC
Title is sort of incorrect. I had a thread running on my injector problems that I think got off track. Reading some other threads here and on other forums, it was mentioned that a dead battery kills the memory of the eec and can possibly damage or impair the workings of some senors.
So back to my thread:
No injector impulse and everything else is either measured as OK or has been replaced and I have 36 lbs in the rail.
I neglected to mention (mainly because of all the difficulties I had pushed it aside) that when I left the car alone for a couple of days, the battery was dead, dead, dead. So to begin to try to get it to start, I had a booster battery on it. When I squirted gas in the intake to start it - no problem but when I stopped it and unhooked the booster - of course the computer lost anything it had.
The battery won't hold a charge now (tried it with two different chargers) as it is getting on in years. Going to get a new battery today or tomorrow.
Anyway, is it possible that this could be my problem?
 
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If that was true, every time a computer was removed from a properly running car, things would break. They don't have problems simply because the power went away. I have swapped the computer in and out of the two 89 5.0 Mustangs I have owned with nothing more that a few minutes spent while the computers and sensors did their learning trick.

I have been fixing mini computers, desktop, and laptop computers professionally for 35 years, and 5.0 EFI Mustangs for 23 years. These computers are really well made and trouble free. Most of the computer problems I have seen are in the heads of the users. Just because they don't understand how it works, it must be the problem.
 
UPDATE:
New battery, learned codes and it works!
I slowly put the car together again and, after each major item was put back where it should be, I would restart it.
Time to move it to the storage place so I have room for the new build that is in transit. Backed it out of the garage and left it to idle. After about 5 minutes - it died. Didn't sputter like it was running out of fuel just stopped like the key had been turned off.
I hit the ignition and it restarted right away. After about 5 minutes again it just stopped. So I thought I would time it to see if this is a regular thing or not.
Hah! It wouldn't start. Back to no spark. No pulse at injectors either however they do have 12v. Fuel relay activates, fuel pump primes, just no spark.
Enough already!
Tomorrow starts the testing again.
 
Follow the testing procedure @jrichker has posted. Then if it says the pickup or whatever is bad, test the wiring (hook up the gator clips and wiggle the wires too!) and trust Occam's (however it is spelled since Siri does not like his name) Razor. If everything else is eliminated, the remaining possibility...
 
Well, it gets weirder.
I went though the checklist and this time everything came down to the coil. So I replaced it and boom! it started right up. Left it running for a while with no issues. Today I start it up back it out of the garage to do tidy-ups on it. Checking timing, fluids, etc. I go in the house to get something and come out and it's dead. Again. Quick check showed no spark. So once again start checking and replaced the high tension from coil to dizzy and it starts rigth up!

I think my car is possessed.
 
Well, it gets weirder.
I went though the checklist and this time everything came down to the coil. So I replaced it and boom! it started right up. Left it running for a while with no issues. Today I start it up back it out of the garage to do tidy-ups on it. Checking timing, fluids, etc. I go in the house to get something and come out and it's dead. Again. Quick check showed no spark. So once again start checking and replaced the high tension from coil to dizzy and it starts rigth up!

I think my car is possessed.
Gotta be a crappy wire or ground or something man.
 
What brand of distributor are you running ?also what tfi module?I know you said both are new but the problems you are having points to a bad pick up coil/bad distributor. I have had a lot of new parts from auto parts stores that i had to take back ..so just because both are new does not mean they are good. Also are you running stock ignition or do you have an MSD box or anything like that? Also have you ever replaced your ignition switch?