Update - I decided to inspect both battery terminals more closely. I noticed that the negative clamp and gunk and a good amount of rust inbetween. So I spent time cleaning it with sandpaper and then baking soda and warm water.

Went to start it... still nothing.

I also tried to resolder some joints on the main relay, didn't help. There has got to be an open circuit somewhere.

 

The main relay has nothing to do with the starter operation.

A quick test for the starter is to unbolt the blk wire and leave the red wire attached. Have someone turn the key to start the car. Measure for with the + meter lead on the blk wire and the - meter lead on the - battery post. You should have 12V when the key is turned to the start position.

Your description two posts up is confusing. I'm not sure if you are testing properly. To bypass the starter circuit you must have the red wire connected from the battery to the starter. Then you must supply 12V to the terminal on the starter where the blk wire bolts (not ground).

A simple way to bypass the starter is to use one wire of your battery jumper cable. Lets use the red wire part of your jumper cable. Hook one red lead to the blk post on the starter. Make sure the jumper is only connected to the post. Then touch the red lead on the other end to the + post of the battery. This should run the starter.

Hope this makes sense and let us know what you find on both tests.

 

You mean on the solenoid right? I think I know what to do but is there a good Youtube video of this? And the other tests? I tried to get the battery cable jumpers in there but it's a bit hard to maneuver and get them in there. (ie I couldn't do it.)

I did the first test but I didn't disconnect the negative cable.

 

Yes, I meant the solenoid post on the starter where the black signal wire bolts. Getting the jumper on the post on the starter is harder to do, so I'd connect that first. Then you can touch on the + battery post.

That black cable is not a negative (ground). It is the signal wire and gets 12V. You don't need to disconnect if you already tested. Did you get 12V?

 

I did that test with the signal wire on the starter. I put a positive clip on it and grounded the to the negative terminal. It was getting 12v through the crappy HF multimeter and my alligator clips. This means that the starter is bad?

If it is getting power but not cranking or clicking, then it is probably bad. Would that mean there is an open circuit?

Related, there is a lot of corrosion on my positive battery cable and it doesn't seem like I can easily cut it off the end. I'm going to replace it.

 

Don't forget to look for corrosion at the "other end" of the negative cable also.

Disconnect the negative. It's way too easy to touch the live end of the positive cable when you're unbolting it from the starter...

 

I did, one of the grounds was really dirty so I cleaned it but it did not make a difference. Still would not start.