The voltage only dips to 11.8 when I try to start, so I don't think that is it. I found another perplexing piece of evidence today. I measured the voltage on the small wire that goes to the terminal while it was disconnected.

After putting the key in and turning it to ACC, voltage is 6.6 volts.
When turned to on, voltage is 9.6v
When turned to start, voltage is full system voltage.
When turned from start to on, voltage drops back to 9.6v.
When turned from on to acc, voltage stays at 9.6v for several seconds, then drops to 6.6v.

Why would there be voltage on that terminal in any position other than start? <img src="/forums/images/graemlins/confused.gif" alt="" />

Also, when I try to start, sometimes I get a clank but no starter motion, sometimes I get nothing. What does that indicate?
Could someone explain in detail the working of the starter and solenoid? I know three things need to happen:
-The gear teeth on the starter need to be pushed into mesh with the gear teeth on the flywheel.
-A set of contacts needs to be brought into contact for a large amount of current to flow.
-The starter needs to spin.

If I replace the starter solenoid, will I fix errors with the first two problems, or just the second one?
Thanks!