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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: OfficialTull on August 05, 2016, 08:48:16 pm

Title: No spark but starter turns engine
Post by: OfficialTull on August 05, 2016, 08:48:16 pm

86 GMC with 79 Chevy 350/350 drivetrain slightly modded been running for 8 months with new drivetrain. No issues, has been running great. Two weeks ago engine shut off while going 40 mph, no warning, no gauge issues, alt fine, oil pressure fine, good gas. Just died. Pulled off the road, towed home. Been sitting ever since. Cannot get any spark at all. At the time of running an Excel blueprint distributor, coils, cap, rotor, ECM. Checked ignition fuse first. Good. Replaced all ignition components, coil, cap, rotor, ECM. No spark. Checked all wiring no shorts. Checked volts at distributor with key on and got 12 volts. Checked volts at the distributor while cranking and got 9 volts. Changed steering column ignition switch, still no spark. Changed distributor even though pickup coil tested good. Still no spark. Ran hot wire from battery + post to distributor and jumpered starter post to crank engine, still no spark. Check plug wires and have continuity on all. Pulled cap to verify rotor rotation and have it so timing chain and cam good. What am I missing. I know I am getting old but never seen this in all my years of mechanic work.

Title: Re: No spark but starter turns engine
Post by: bd on August 05, 2016, 09:50:27 pm

Married or divorced ignition coil?  When you stated you replaced the ECM, did you mean the ignition control module inside the distributor?  Are you using an external CD ignition box?  The symptoms are reminiscent of a faulty pickup coil.  Remove the distributor cap and unplug the pickup coil  Connect a multimeter across the pickup coil terminals, set the meter to between 3 and 10 volts AC and crank the engine.  Is there a reading?

Title: Re: No spark but starter turns engine
Post by: VileZambonie on August 05, 2016, 10:33:25 pm

If in fact your issue is no spark and you have verified everything you say and that the distributor is turning, you basically have 3 possibilities:

Ignition control module

pickup coil

ignition coil

Perform the test BD stated and tell us if you meant ICM instead of ECM. Also measure the resistance across the pickup coil with it disconnected.

Title: Re: No spark but starter turns engine
Post by: OfficialTull on August 07, 2016, 04:18:47 pm

Yes meant ICM. Pickup coil resistance measures okay. We pulled the hot wire to the distributor with key off, put positive probe from volt meter on connector and accidentally touched the negative probe on the on the three wire connector ground wire on the distributor and it had continuity. We then set voltmeter to measure voltage and with key off put negative probe of the volt meter in hot wire connector and the positive probe of the volt meter on the positive post on the battery and measure 12.8 volts. Should the hot wire feed to the distributor be grounded in a key off position? We tested the hot wire to the distributor earlier for continuity to the ignition fuse and it we had continuity. Thoughts?????

Title: Re: No spark but starter turns engine
Post by: OfficialTull on August 07, 2016, 04:32:41 pm

Ignition coil is married. Just tested the ACV across the pickup coil but my meter only has options for 200 and 500. I set it to 200 and got a reading of "00.3" while the engine was turning

Title: Re: No spark but starter turns engine
Post by: VileZambonie on August 07, 2016, 05:58:09 pm

what was the resistance reading? It sounds like the ignition module bit the dust.

Title: Re: No spark but starter turns engine
Post by: OfficialTull on August 07, 2016, 06:23:57 pm

938 i believe. I've also changed out the ignition module, I'll take and get it tested to make sure though.

Title: Re: No spark but starter turns engine
Post by: Irish_Alley on August 07, 2016, 07:26:32 pm

does this help
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29995.0