Need help running down why my starter solenoid is not getting 12 volts when trying to start the car.  I just hear a slight single click when the key is turned and car won't start.

I have 12.65 volts at the starter and when I put 12 volts across the solenoid the car starts right up. The battery has been tested and it is good. The starter relay and neutral safety switch are only two years old so I don't think they are the issue.

Not sure if anything in the fuse panel relates to the starting system.  Only thing I can think of is the key ignition switch maybe.

Any help would be appreciated..

I'm sure you have checked, how bout grounds? Also tight connections. 

I cleaned up the negative ground to the frame and that got me from 11.5 to 12.63 volts at the starter not the solenoid.  Will have to pull apart the center counsel and see if something came loose under there. Thanks

Hi, If it's a standard Delco with the comparable solenoid,  they are relatively easy to rebuild in your shop. The fine wire inside the black nose needs to be intact. The fork that engages the plunger for the flywheel needs to be free, non binding, and the washer that connects the two posts inside need to have good contact. Just flip the washer if it's pitted to make good contact. Bench test it with a battery before installation to make sure it works. I know a growler may not be available,  but the armature needs to be good too. Keep us in the loop.

Woops, forgot to say the fork can be turned over too, to give a new surface for the engaging clutch. 

Old school -- fix rather than buy new -- I like it!

I assume by “the negative ground to frame” you mean the negative battery cable. Be sure you also clean the engine ground strap to the frame - that’s the one the starter needs to complete the circuit to the battery. It’s bolted to the motor mount  

The engine ground strap and the negative battery connection to the frame are both exposed to the elements and prone to corrosion. 

Thanks everyone who responded. It turned out to be my neutral safety switch which was less than two years old. It separated slightly from moving the shifter back and forth and the contacts and springs fell out of place.  On a positive note, this problem caused me to look at the battery ground which I cleaned up and now have full 12.6 volts going to the starter. Had less than 12 before. Pops right over!!