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I have power to the new coil I replaced in my 1992 chevy blazer 4.3 litre. I do not get a spark from the coil when cranking.  I have tested the red wires on the 2 plugs going into the coil and there is power in both.
Any ideas what the white wires do on these plugs and why I am not getting a spark from the coil?

Is there something I am missing?  Seems like power to the coil should result in a spark or power to the tip of the coil that the plug wires connect to the distributor.

I am stumped...........

Mike  

I have power to the new coil I replaced in my 1992 chevy blazer 4.3 litre. I do not get a spark from the coil when cranking.  I have tested the red wires on the 2 plugs going into the coil and there is power in both.
Any ideas what the white wires do on these plugs and why I am not getting a spark from the coil?

Is there something I am missing?  Seems like power to the coil should result in a spark or power to the tip of the coil that the plug wires connect to the distributor.

I am stumped...........

Mike  

you probably have a bad ignition module...  but you might be much be better off with a complete reman distributer..

before you do anything .. take the cap and rotor off... stick you nose right down where you can see the top of the distributer shaft.. take a look for cracks in the magnet as shown in the image...



you should also carefully examine the play in the distributer shaft..   stick the rotor back on and see if it wiggles.. it should NOT.

i have had others so bad that the reluctor tips  were bouncing off the pick up coil tips...


this IS one brand of reman 4.3 distributers...  note the difference .. you won't believe how much better it runs with this one..





please.. preset the crank with the rotor pointing toward the number one spark plug wire position.. and even fine tune that .. so the teeth of the reluctor are perfectly aligned with the teeth of the pick up coil before you remove the distributer..  note the position of the crank..

this allows you to remove and replace the distributer.. align the housing so the tips or the reluctor and the pick up coil are aligned again..   this is after you have verified that it is fully sitting down on the oil pump shaft..


more to come  

how the electronic ignition works....

the red wire to the positive side of the coil and to the B terminal on the HEI module... has switched 12 volts on it..


the white wire from the negative side of the coil to the C terminal on the HEI module.. is the other side of the coil control...

inside the ignition module is a power transistor...   that connects the C terminal with one of the hold down screws.. to make or break ground to the white wire..

when the module grounds the white wire.. the coil primary is filled with electrons building a magnetic field...

when the power transistor opens the magnetic field collapses and creates a high voltage spark in the secondary wirings...


how it knows when to fire the spark.. is done by the pick up coil and the reluctor..   as the shaft rotates. the tips of the reluctor on the shaft move past the tips of the pick up coil..  it generates a small electrical current.. when they are coming closer together.. the voltage is above 0...  usually about half a volt above until the tips line up perfectly.. at that point the voltage drops to 0..  the power transistor switches and opens and the coil discharges..   as the tips move apart.. the voltage goes into the negative until they start getting closer again..

you can test the pick up coil with an ohm meter..   set it to 2K ohms..    500 to 1500 ohms .. usually around 900 is expected..

before disconnecting .. switch the volt meter to the 2 volt AC or 20 volt AC setting..  spin the shaft.. you need to see just over 1.0 volts AC..  if it does not reach that ac voltage.. it won't work the module...  no spark will be created..

thats the rough how it works...