I have a 84 corvette, I changed the HEI coil ignition module dist cap and rotor, I have no spark, the rotor turns, If I put 12 volts directly to the distributor, I still get no spark

Have you ever heard of the "mechanics rule" that says if it ain't broke don't fix it? Put the old coil and module back in they're not part of a tuneup because they can last for the life of the vehicle or not lol. I hope this helps. Take Care.

My first concern is: how do you know there isn't fire? Did you
1- Check it with a screwdriver inside the spark plug wire at spark plug end to ground. This isn't the right way.
2- Have you check fire with HEI spark tester.
(The right way). To see a spark with the tester there will be 25k the spark to jump to ground and it test the coil working properly.
Now the fire system or ignition spark work this way.

When the engine is turning up to 400rpm the camshaft gear inside the engine makes distributor shaft turning. We often see the distributor gear at the end worn like an eaten apple.
Remove the Dist. Cap Somebody starts the engine look for the rotor if it turns. This will tell you the gear is OK.
P.S; What you call the SENSOR = Ignition Module just to let you know
Hope it helps

Possible ignition starter switch problem.

I guess you could have the ignition analyzed on an oscilloscope. Maybe a tech could see something then.
I always heard the only gap was the spark plug gap-the rotor has no gap-are you sure you got the correct rotor? And does it touch the top distributor cap coil wire tower?

Let us know. It is a mystery worthy of a solution.

I owned a similar 1986 caddy

12 Volts on pink wire to dist with key on

The top of the cap is the HEI Ignition Coil

Inside dist is the pickup coil (no crank sensor)
& ignition module with the 3 or 4 wires

Maybe the module failed- if you have no spark
at plug wires

HEI distributor and burning coils,it in you connection first make sure you install primary and secondary prorperly as it comes out of the cap , and inside the cap wire from modules dont make contact if you are burning its from primary circuit, this is the (B+) or (battery most likely), your secondary is your tach and that need to switch from postitive to negative for it to create spark obvously if tach was grounded or applied power you wont start,but there are times the condensor in the distributor does stays fixed and shorts out the coil (replace that condensor its for suppression) when the condensor is replaced run a fused direct wire at B+ (from ignition) run the vehicle and monitor the tach wire and check to see if that get hot

Fred,
Did you check for spark at a plug wire or at the coil wire? Check at the coil wire,if there is spark there,the ign rotor is bad,very common to have the hot spark "drill" a hole thru the rotor to the dist shaft. Also check for play at the rotor shaft. Distruibtor bushings tend to go bad,making the trigger wheel hit the pickup coil,killing the spark.

How about the MAP SENSOR? Do you check it out?

module is under dist. rotor inside cap

It would be great if you could find the Ignition Control Module!!! From my experience on my Jeep...90 YJ 4.2 liter carb. it does not have one...Computer controlled only...