No spark problems.

[Wyatt_wade]

In my 86 I’ve got a 383 with an MSD hei distributor. My probable for the past few weeks is that I don’t have any spark when the engine is cold. Get in the truck to go to work in the morning- no spark, get in after it’s sat more than a day- no spark. The starter turns over fine and I checked with in inline spark tester. Though I know the battery is fine because it’s new and I had this problem with the previous one, you can slap some jumper cables on there and it’ll fire right up. And after it’s gotten going it will have no trouble starting as long as it’s warm. I obviously have a voltage drop somewhere I’m just not sure where to start, any help would be appreciated.

 

[Vbb199]

Too wide of a sparkplug gap possibly?
Or timing a little out?

This problem is a bit beyond me. Lol

With key on, cranking, is the coil getting the full battery voltage?
(12-14v)


Either that or the little Module under the cap is faulty maybe.


Those would be my first places to check, the sparkplug gap was kind a shot in the dark that probably has no real validity

Last edit, because something is coming to me, definitely start with that coil, seems like I recall something about weak coils not working when they're cold, but once hot, they work.

 

[AuroraGirl]

Too wide of a sparkplug gap possibly?
Or timing a little out?

This problem is a bit beyond me. Lol

With key on, cranking, is the coil getting the full battery voltage?
(12-14v)


Either that or the little Module under the cap is faulty maybe.


Those would be my first places to check, the sparkplug gap was kind a shot in the dark that probably has no real validity

Last edit, because something is coming to me, definitely start with that coil, seems like I recall something about weak coils not working when they're cold, but once hot, they work.

screwy little fuckers arent they

 

[Vbb199]

OP, what did you come up with? I forgot this thread existed

 

[Vbb199]

screwy little fuckers arent they

They can be, sometimes they'll cause a whole damn mess of confusion, anger, swearing, and begging for forgiveness

 

[Grit dog]

Like VBB said, doubt it's plug gap.
Did you verify no spark at the wires or it's just not starting.
Aside from verifying battery condition and grounds, although old chevys aren't very finicky with respect to battery condition. If there's enough juice to crank, there's enough to fire typically. Test continuity/resistance on hot lead to the coil, maybe even rig in a jumper wire to verify or eliminate that.
My money is on the coil. Copper alloys have some of the highest coefficients of thermal expansion compared to most other metals save for some aluminum alloys. A broken or degraded winding or few in the coil could lose continuity when cold, but the extra energy from a jump start could be enough to expand and re-gain continuity . Could happen opposite as well. Thermal expansion causing a short.
HEI, it's a coil module on the dist cap, correct? If external coil model, coils can go bad and short to the case. Although, that I've seen usually happens opposite, shorted when hot, can hear or see arcing in or on the coil. Buddy just replaced a (external) coil on his boat. 305 chevy motor with traditional coil. Cold engine ran fine. Heat soaked, the coil would arc/spark and run like chit or not at all.

 

[AuroraGirl]

They can be, sometimes they'll cause a whole damn mess of confusion, anger, swearing, and begging for forgiveness

my coil was rusted, broken metal square bar around it, and had bad connection terminals.

didnt ever cause issues

 

[AuroraGirl]

A good way to verify coil working condition is to find the hot side of the coil and ground it out, the gentle heart-stopping shock will let you know it works.



I accidentally provided a ground to a K series kohler coil.

I do not want to do that ever again.

 

[82sbshortbed]

That's the capacitor. That used to be a little prank at the parts store. They d charge one and lay it on the counter. Then someone would pick it up just looking at it and when pow it would shock them and everyone would laugh. Cause it hurts. Lol

 

[AuroraGirl]

That's the capacitor. That used to be a little prank at the parts store. They d charge one and lay it on the counter. Then someone would pick it up just looking at it and when pow it would shock them and everyone would laugh. Cause it hurts. Lol

No, im talking about the coil. The points close to their gap to provide a ground for the spark to fire the plug. with direct touching of that with a multimeter, but i didnt insulate my hand and had it touching barb. i was trying to find out if the points were bad because key on, engine off, the left should be hot. and if the points cant provide ground...
points failed from bad condensor

 

[Poppy 87]

As you stated HEI would eliminate points and capacitor. I lean towards coil as well. The ignition control module typically are not intermittent, either they work or do not.