Electrical please help! ive tried everything! no spark from coil!

[conigz]

hello,
im new here but really need some help.
i just put a new tremic trans in my 89 lx coupe. only ran it 2 times and then just died. no spark seems to be the problem. I have replaced the coil, tfi and bought a new mega squirt computer. (kind of an excuse because i always wanted one.) still no spark. just replaced my msd distributor. still nothing. the ignition module is only 2 years old. im running out of ideas except a whole new wiring harness. i did notice today after installing the new distributor that when putting a test light on the coil when cranking the test light shuts off. this is like my 4th child and i am pulling what ever hair i have left out. please help with any ideas! and not the normal checklist that is always posted. went through all of those.

 

[conigz]

also when cranking. for some reason the gas gage goes up. maybe that is normal and i have never noticed it before?

 

[Mustang5L5]

There’s a fusible link in the harness near the master cylinder. This powers the coil. Make sure it’s not blown

 

[conigz]

There’s a fusible link in the harness near the master cylinder. This powers the coil. Make sure it’s not blown

I will take a loom now. it is getting 12vs to each though.

 

[CassieL]

So start from scratch. Test the coil the work upstream from there.

 

[conigz]

2 new coils that are both getting 12v. Brand new msd dizzy, brand new computer. I still get nadda

 

[Mustang5L5]

If they are getting 12 v then the fusible link is fine.


Relevant wiring

It’s lacking the signal from the distributor

 

[Praetorious]

You rarely need a new wiring harness, dont just throw parts at it (unless you're just loaded with money)

You mention a new computer,is your old one still working and in the car? you might have to start working backwards till you get to the point where the problem started,if you try to ground a spark plug i guess there is no spark? from what you tell in your first post it sound like it could be computer related,i have 2 of these cars and ive had them for several decades and while im no expert i have dealt with just about every situation they can throw at you, on both of my cars (89 and 91) i have never had a fusible link go out on me,not saying it can't happen but its been rare for me.

You dont have a MSD box or anything like that?

I had this issue once for a couple of years where my 91 would die every so often, just flat out die in the middle of traffic,if i went out to the coil and tapped it it would start right up,this went on for a couple of years even after changing coils,you know what it was? that little silver looking box that controls your power windows and its bolted with all those wires on the starter solenoid,it was about a millimeter from the coil bracket and it would short out every so often killing the car, one night i had someone else fire up the car and i saw it arcing,once i got that fixed that problems been gone.

Sorry i cant be more helpful,just throwing stuff out here,lots of guys here are super smart when it comes to these cars,I'm sure they will figure the issue out with your car.

 

[conigz]

No. Its a TFI MSD. Brand new. So bow i havs a spare i guess. What does it mean when the test light is good on the distribitor them goes out when cranking?

 

[CassieL]

No. Its a TFI MSD. Brand new. So bow i havs a spare i guess. What does it mean when the test light is good on the distribitor them goes out when cranking?

No. Its a TFI MSD. Brand new. So bow i havs a spare i guess. What does it mean when the test light is good on the distribitor them goes out when cranking?

No. Its a TFI MSD. Brand new. So bow i havs a spare i guess. What does it mean when the test light is good on the distribitor them goes out when cranking?

 

[CassieL]

Test the tfi module for coil trigger. At the module

 

[Praetorious]

How are you testing this? where do you have the test light hooked up to? usually if you lose spark when cranking its usually your module,these things are famous for going out on these cars,there was actually a lawsuit in the early days about them.

Before you installed the transmission everything was working fine? any chance you might have disturbed something? you need to source another module and test it with that, when you swap them out be careful when its going in, those electrical contacts are really thin, make sure its going in straight and use artic computer paste on them,that dielectric grease is good but artic paste is better.

 

[Praetorious]

Meant to say use artic paste on the heat sink on the distributor that mates to the TFI module,NOT on the contacts.

 

[conigz]

Meant to say use artic paste on the heat sink on the distributor that mates to the TFI module,NOT on the contacts.

THe tfi module is brand new. Its acually my 3rd one. I ordered one from LMR. Then got one from napa in case they sent me a dead one. Now this is a brand new distributor that came with one. And i read my post from yssterday. I meant to say test light on the coil goes out when cranking. Its supposed to pulse not go out.

 

[conigz]

Little update. But maybe a start? I unplugged the computer (which is the stock one right now.not the mega squirt, which none them worked and did the same thing.) Tried to fire it up and see if i had spark. It almost started on the left over primed fuel. I believe that both computers are good. I suck at wiring! What does that mean?

 

[Praetorious]

Seems like you are on your way to success,bad connection somewhere? problems like these are hard to figure out,i told you the story about that little silver box that was arching on the coil bracket and how one of my cars would die every so often, something else i remembered that i had hell with was the following... on the drivers side next to the firewall there is a ground strap, its bolted from the back of the head to the body of the car,mine was green with corrosion and no matter how many times i would try to start the car sometimes it would and most of the time it wouldn't.

These cars are very finicky about grounds,ive seen cars with grounds dragging under the car and they run great, these cars dont, when swapping computers,did you reinstall your computer ground by the kick panel?

That's awesome you have extra TFI modules now,once you get your car going get you a little box and put a coil, a TFI module and the smallest tools you can find to do the job and put that little box in your trunk,i got one and it makes me feel a lot safer when i'm out and about, last time my module went out it was in the middle of traffic and i had no triple A or anything like that, it cost me 150 bucks to have my car towed 2 miles to my home,not happening again.

 

[conigz]

Seems like you are on your way to success,bad connection somewhere? problems like these are hard to figure out,i told you the story about that little silver box that was arching on the coil bracket and how one of my cars would die every so often, something else i remembered that i had hell with was the following... on the drivers side next to the firewall there is a ground strap, its bolted from the back of the head to the body of the car,mine was green with corrosion and no matter how many times i would try to start the car sometimes it would and most of the time it wouldn't.

These cars are very finicky about grounds,ive seen cars with grounds dragging under the car and they run great, these cars dont, when swapping computers,did you reinstall your computer ground by the kick panel?

That's awesome you have extra TFI modules now,once you get your car going get you a little box and put a coil, a TFI module and the smallest tools you can find to do the job and put that little box in your trunk,i got one and it makes me feel a lot safer when i'm out and about, last time my module went out it was in the middle of traffic and i had no triple A or anything like that, it cost me 150 bucks to have my car towed 2 miles to my home,not happening again.

Since the fuel pump still primes I'm guessing it's not a computer problem. To be honest I don't think the old stock computer was even bad. Like I said. I just really wanted a tuneable one.

 

[Praetorious]

The problem was never fuel though, just spark correct?

Have you checked your ignition switch in the column? thats another possibility, on my 91 i replaced it about 2 years ago, that thing was melted, it was a miracle it was still working, have you checked your clutch safety switch after you installed that new tranny? could that be stopping the car from starting? both of my cars are autos so Ive never fooled around with clutch safety switches, i know you said you recently installed a tranny, i think these switches can be temporarily bypassed to see if they could be causing a issue?

 

[conigz]

The switch is 2 years old. Same problem as you had. Melted and fell apart. I check the voltage. Everything seemed to be normal.

 

[Praetorious]

This is gonna be something you have overlooked, you have everything new or have several spares and nothing is making a difference,i know you said you replaced your tranny, something was disturbed somewhere,a switch, a plug, something is loose or by coincidence decided to go south at the same time ,thats happened to me many times,something is not making contact to keep that spark going, you might need a new set of eyes on it like a friend or someone thats familiar with these cars, i would be happy to help you but I'm nowhere near you.