03blackburb

1985 C10 5.7 died the other night. Checked it out and no spark to any cylinders. Checked out the coil pack on top of the distributer and it was shorted. Replaced the cap, rotor and coil pack. Voltage is good to the distributor. Got it all back together with the new parts and still no spark.
Ideas??

JHH

I dont know if you have it running yet but I think that those had that electronic spark control system. If so jump terminal A to C and see if it starts.JHH

03blackburb

tested the pickup coil and it checked fine.
Had the ignition module tested and checked out fine.
checked the capacitor and it also checked fine.
the ground is good.
Verfied all the fuses, which checked out fine.

Terminal A and C on what module or component?

golfer

I'm guessing the shorted coil was on the secondary side.

You hadn't mentioned about changing the wires and plugs.

You can't always trust new parts since they've been known to be junk out of the box.

I'm not sure how the ignition module was tested but I wouldn't trust it .... you might want to replace it. Just make sure to apply the heatsink silcone grease to the backside of the module or it will overheat and be destroyed.

You're 100% sure about the pickup coil.

Worst case is the distributor is worn.

03blackburb

the ignition module was tested on a module tester. The test was run multiple times with no failures.

Plug and wires don't come into the picture as there is no spark coming out of the distributor toany of the terminals.

A worn distributor would not cause a no spark condition. It would show up as rough running or eratic running. There would still be some spark.

JHH

Sorry that I havent got back sooner. See if the distributor has a 4 or 5 wire connector on it. If so then unplug it and leave it unpluged and jump A-C. I think this is right if I can remember correctly. Hope this works for you. A-C on distibutor side of connector not harness side. JHH

two slow

Is the rotor turning inside the cap? I had a gear break on a distributor once.

03blackburb

The rotor is turning when the engine is cranking.

JHH - Are you speaking about the connector tht goes to the ECM?

JHH

No. I am refering to the connector on the side of the distributor ( if it has electronic spark control )
It is a 4 or 5 pin on the passenger side of the distributor. ( tailgate has emblem on them that said elctronic spark control) The control box is behind the glove box but dont do anything to that. JHH

The ECM as you are talking about is probably what I am calling the control box. I dont think any of those trucks had ECM till 87 ( fuel injection) I could be wrong. Hope this helps. JHH

golfer

Not quite true ...if the rotor shaft of the distributor is not turning then there would be no spark at all.

You indicate the rotor is turning so that won't be the case.

On my 86 C20 with a carb. there is no spark control box or ECU simply a HEI type of ignition. This consists of the coil in cap with a pickup coil and ignition module ( in place of breaker points ).

1 - Check the ohms reading of the coil between the red (BAT / B+ ) and the yellow ( TACH / C- ) should be between 0 and 1 ohm and each one of those to ground should be infinite ohms.

2 - check the ohm reading of the center contact inside the cap to ground ... should be between 6000 and 300000 ohms. Make sure the spring is contacting the coil

3- check the contact strip of the rotor for continuity

4- is the rotor contact swiping the contacts in the cap

5- check the ohms reading of the green and white wires from the pick up coil ... should be a steady 500 to 1500 ohms when flexing the wires.

6- check continuity for the three wires ( brown , black , pink ) coming from the distributor base to the cap.

7 - check for broken teeth of the pole piece ( stationary magnet ) and / or the rotating pick up.



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