No spark, no ground to coil?

[Nordin]

Hi!

I got some issues with no spark since last friday, been poking around with my volt-meter and I found that there is no ground, or 12v for that matter to the coil. There is both 12v and ground to the ICM.
I don't know if its supposed to give me a reading on the volt-meter or not but...
No readings with key in on but engine off or while cranking.

Could it be some ground issue? If so, is it possible to cut the black/white cable and ground it somewhere?

Thanks!

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[PlayingWithTBI]

The ICM grounds the coil when told to by the ECM. There could be other issues.

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Here's a troubleshooting guide that may help.

How To Test The GM Distributor Mounted Ignition Module

GM 4.3L, 5.0L, 5.7L Index of Articles

easyautodiagnostics.com

 

[Nordin]

Thanks for the troubleshooting guide, I have done the steps.

I have a brand new ICM with 12v and ground but the issue here is that I don't get 12V or ground to the connector on the coil.
Tried to understand the circuit diagram you posted but I do really suck at electrics...

Suggestions anyone?

 

[Schurkey]

The two-wire connector you're holding should have voltage anytime the key is "on", on one of the terminals. The other terminal would have ground only when the module is triggering a spark.

 

[Nordin]

The two-wire connector you're holding should have voltage anytime the key is "on", on one of the terminals. The other terminal would have ground only when the module is triggering a spark.

Really? That connector goes into the coil and not the ICM

 

[Schurkey]

Really? That connector goes into the coil and not the ICM

Yup. One wire to provide voltage to the coil, the other to selectively supply ground. If the module has power, but the coil doesn't...the wire harness is likely defective.

 

[Nordin]

Yup. One wire to provide voltage to the coil, the other to selectively supply ground. If the module has power, but the coil doesn't...the wire harness is likely defective.

Thanks alot! The ICM has both 12v and ground but the coil-connector doesnt have 12v or ground.

guess I have to start look into the harness then

 

[Nordin]

Traced all wires in the harness from the connector and cant find any obvious damage. God damnit

 

[Nordin]

Well I managed to get power to the coil but still no start. And the coil should be OK according to the meter. and the rest is new.
no fuses either, could it be a relay?

 

[Schurkey]

Well I managed to get power to the coil but still no start.

You need power, AND you need the module to ground the coil in pulses. Grounding the coil permits current flow, which creates magnetism. When the module breaks the ground connection, the magnetic field collapses, and you get a spark. The ground is not continuous.

And the coil should be OK according to the meter.

A meter cannot tell you that the coil is good. A meter can tell you that the coil is bad.

Coil testing for most of us involves the meter, AND a spark-tester calibrated for HEI ignition systems.

This is the kind of spark-tester I favor:
www.amazon.com/dp/B003WZXAWK/?coliid=I3S98D7T1J0RLJ&colid=2VLYZKC3HBBDO&psc=1&ref_=lv_ov_lig_dp_it

and the rest is new.
no fuses either, could it be a relay?

"New" doesn't mean "good". What parts did you replace?

If you connect a test light to battery +, then probe the ground wire on that two-wire connector you pictured earlier, the test light should flicker when someone turns the key to "crank".

It's unlikely to be a fuse or relay.