I have a '91 Formula 305 5Spd, which was running fine then out of nowhere it wouldn't start. Every once in a while it will start up and run, I thought the VATS chip may have been worn but I tried 3 different keys and the same problem still existed. The car will crank but not fire up...I can hear the fuel pump kick on, and I have around 45 psi at the rails. The oil pressure is good and the battery is fine.
My next test would be the coil but I'm not exactly sure what the correct ohm reading should be. I have a Accel Electronic super coil in the car. Any clue on what the reading should be? And do I need to disconnect it to get an accurate reading? I know I can take a plug out and check for spark but I would like to see what the output is from the coil. I'm hoping that its and easy fix and not a total guessing game on what could be wrong, especially since it's not throwing codes.
Any feedback would be great.
Thanks

 

First check if you have spark. It could be the coil, distributor cap, pick-up coil, or ICM. Get a spark plug tester and put it in line with a spark plug and see if you have spark, If not, move the tester to between the coil and cap and see if you have spark. Mine turned out to be a pick-up coil and then the ICM went out. A Chilton's, Haynes, or service manual will tell how to check the coil with an voltmeter. Good luck.

 

I assume you did check for codes? If there is a VATS issue its good chance you will see a code.

The coils are pretty stout. I have had four cars and never lost one yet. On the other hand I have been through many ICMs (ignition control module).

The small distributor cars are known to go through them. Heat problems.

Same advise as 1fast91 -- check for spark and test the coil.

If you do need an ICM do not get a cheap replacement this is one place you must spend for quality. And be liberal with the dialectic grease.

best regards

 

Thanks for your help.
Will post back with results when I am able to get out to the garage to see whats going on.

 

Eeeeeezie enough to test the coil by putting a plug wire on the output terminal and a spark plug in the other end, tie the shell of the plug to ground with a piece of bare wire, make sure your battery is freshly fully charged, have your assistant crank the motor, and see if it sparks. Look for NICE BIG FAT LOUD SNAPPY purple-white sparks about as big as the center electrode; not little weeeeeek hard-to-see blue ones like your lawn mower, or yellow-orange ones.

Any coil should measure very low resistance from the batt terminal to the ICM terminal (fraction of an ohm... VERY hard to discern from a short), several hundred up to a couple of k from the batt terminal to the tower, and open from all other terminals to ground. An exception would be if you measure open from the tower to batt and the several hundred from the tower to ground, it being possible to connect the secondary winding that way at the expense of REQUIRING a ground connection to the coil which doesn't exist from the factory.

Bad ICM is more likely than a bad coil. Bad rotor is also very likely: the small-cap rotor fails by arcing through the center, the failure is almost invisible.

 

Turns out I wasn't getting any spark, it was a bad ICM. Also replaced the cap and rotor while I had everything off. The terminals inside the cap were corroded and the rotor looked worn. Runs much better now and fires up with a lot less cranking.
Thanks for all your help guys.