help with freakish non start problem
 

I can't for the world of me figure out what to try next. First the back story.
I drive my 82 SC into the driveway at night with absolutely no problems. Turn it off, again no issues running or stopping. Come back a few days later, turn key and the engine starts to turn about a 1/4 crank then stops. No drama just stops. So turn key again and nothing but a small click from the solenoid.
I check the battery. It's fine, fully charged and showing 12.6 Volts.
I replace the electronic part of my ignition switch just because it was really old and while I was trouble shooting this I didn't want it to fail at sometime in the future.
Check the voltage at the solenoid and it's getting 12.4 volts from the yellow terminal 50 wire from the starter. Remove and clean ground strap.
Try again and no start. Figure it must be a bad starter. Replace starter. Same thing, no start. Pull starter and check flywheel ring teeth. Fine, all there. When I try and start it there is no dramatic sounds. No grinding, no high speed spinning. Nothing but a click and hum.
I'm at my wits end as to any direction to check next. Never had this problem before.
Please help

Steve

Sorry. I should have mentioned that the battery is new and that I had it load tested as well. it checked out fine.
Thanks Jared. And the mystery continues............

Can you turn the motor over by hand or is it bound up?

Thats next on my list.
I am kind of dreading trying to turn it over, just because for the world of me I can not figure out how it would freeze or seize just sitting for a few nights. There is the right amount of oil in the trans and engine and was not running hot or any problems when running last.
Please keep the ideas coming

red wire to the msd or whatever ignition you might have?

OK
So the car is in the air. I took a deep breath and the engine turns freely. Put it in gear and the engine and trans turn together fine.
Which red wire?

Here is a great troubleshooting procedure for a non-start:
Pelican Technical Article: Starter System Troubleshooting

Just follow it and you will find your issue.

You didn't say if you had 12.4 V to terminal #50 while trying to use the starter? There must be a load on the circuit for the test to be meaningful.

Yes I have 12.4 volts to the 50 terminal on the solenoid while trying to crank.
I just tried to jump the car incase the battery test was wrong but I had the same results
I know the battery is good.
I know the starter solenoid is getting 12.4 volts.
I have cleaned the ground strap
I have a new load tested starter
The starter makes a noise but does not engage.
Also this is the second starter because my friend dropped the first new breaking off the solenoid one when I pulled it to check on the fly wheel ring teeth. I had to buy a second one

Try attaching the ground clamp of your jumper cables directly to the starter body. Does it crank now?

What about the big red wire carrying +12 directly from the battery? What is the voltage on it when cranking? Could it be shorting somewhere? Like in the alternator?

One thing that is easy to do is to run jumper cables from the battery directly to the starter. Clamp the negative cable to the frame of the starter and the positive to the big connecting post on the starter and see if the starter spins when you jump the positive lead to the starter solenoid. If it does, you have a bad cable running from the battery compartment to the starter or maybe a bad ground right at the battery. You can do this with long jumper cables or move the battery next to the starter.

I would try cleaning the ground strap connections again, use some sandpaper and clean the body surface and the connection so that there is no corrosion. Clean both ends of those connections down to the metal.

Good Luck, Shane SmileWavy

So.......
I've got 12.45 volts when measuring directly terminal 30 on the solenoid (power from battery) before cranking.
When I crank it the voltage drops to 0.65 then when I stop cranking it goes back to 12.45
I can hear the solenoid engage but the motor does not spin.
What next guys?

I will try grounding the trans directly to the body with a jumper cable next to eliminate that

I'm thinking that's it.

On mine, I ran a second ground (just one from a local franchise auto parts place) from the body by the trans (the same bolt as the stock strap) to the top starter mounting bolt. (It's been a while, but I think it might have been a Warren Hall suggestion.) That solved a lot of starting problems for me.

Good luck,
Shawn

If I had a bad ground right at the battery wouldn't everything be effected?
Could there be a short somewhere in the alternator?

There's a condition known as "high current density" which describes what may be affecting your car. Somewhere along the electrical path is a corroded connection which is trying to pass more current than it is able. Voltage will read normal but not enough amps can pass to do the job you need. Connecting directly to the battery from the starter will rule this out. Just set a second battery on the ground next to the starter and hook the jumper cables directly to the starter. If the starter starts and the car runs you know the problem. I have had to do this before and it told me the problem. The battery in the car can pass enough current to the other electrical parts to run them but not enough to turn the biggest consumer, the starter. It isn't the battery's fault but rather some weak connection along the electrical path. Chevy trucks with side posts on the battery are famous for this problem.

White crusty corrosion inside the terminals, or a bad wire connection inside the terminal, or a battery that has given its all.

Rex is right on.............
 

Rex is right on...I just went through this with my 73.................and the 71 before it....Attach a jumper cable from the ground point that the battery negative attaches to (chassis ground) and then back to the starter flange...or closest ground point..............I'm betting it will crank.

Regards,

Al

PS: then replace the ground strap, clean all chassis ground points etc...

I'll take "bad ground" for 500 Alex.

^^^^ This.

Check your grounds first, if that doesn't do it, then my vote is to clean the 14-pin connector in the engine bay and the connector where the ignition switch harness plugs into the firewall.

Something is passing voltage but it isn't a good enough connection to pass the current you need.