hey so in my 75 88 , its been sitting a while and i get no spark. do you guys think that battery dropping to 10.5 volts during crank would stop the coil from making any spark?

 

I drove my car with no alternator until the battery was so low that the engine died (below 9 Volts) , so I doubt that 10.5 Volts would result in no operaton at all.

But that is a very low battery (practically dead) so connect a charger and bring it up tp full voltage and try again.

 

Dead battery....

 

It's possible, jump it with a known good battery.

 

First, since you're in Alaska, make sure the battery didn't discharge so low that it froze. I've never known anyone to save a battery that had frozen. Jumping it could cause a battery explosion which you do not want.

If the electrolyte is verified to be liquid, slow charge the battery till it starts taking a charge, 2 amp rate or at as low a charge rate as your charger can be set. Preferably out of the car.

Once battery voltage is up to about 11.5v, you can then charge it normally.

 

I wouldn’t think 10.5 volts to the ignition WHILE cranking would cause a problem. I’d make sure the battery is fully charged, and try it again.

Have you checked for spark? Does the engine crank slowly? What’s the condition of the cables?

Put a test light on the tach terminal of the HEI distributor. Turn on the ignition, does the light come on? If not, with the coil is defective, or you have no power to the ignition. Leave the test light on, crank the engine. The test light should flicker. If not, the module or pickup coil might be defective.

 

Your'er the only one who read and understood the info from the OP. And yes 10.5 is fine when cranking. Without me pulling service info I believe the spec is at least 9.6 during cranking.

 

He also said car had sat for a while, so the assumption is the battery is discharged to a voltage below where the starting/ignition system is functional. No info how long it's been sitting, whether it had been charged before he tried to start it, whether it had a trickle charger on it. Plus he's in Alaska where it can get cold. Lot of unknowns and variables.

Charge the battery and go from there. Course he hasn't followed up since his original post either, so we don't know if he ever got the engine started.

 

Other than the first reply to him, that is.

 

Yes. You are correct. My mistake.

 

If I'm not mistaken, the "pull-in" voltage most often cited (required) to engage a coil is ~80% of available voltage. Therefore, .80 x 12V = 9.6V. However, in reality, I believe the pull-in voltage required to energize a coil is often ~50% - 70% of available voltage (6.0V - 8.4V). If the OP has an available voltage of (which he stated was measured at the battery) 10.5V, I don't believe that is enough voltage to pull-in and energize a coil (5.25V minimum @ 50% load).

 

You are very much mistaken. Stay in your lane.