On 18 Jun 2003 19:03:42 -0700, (Teffy)
wrote:

When the key is in the start position, I measure these voltages:
8.0 v across brown wire from ignition switch to solenoid S10 terminal.
7.2 v from solenoid terminals S10 to S2 (terminals with small gauge
wires).
0.5 v from S2 to battery negative terminal.

You sure the battery is good? I'd be a little concerned about the
drop from 12v to 8v during starting. Is the starter motor getting the
8V? A battery in nominal condition and in 70F temperatures ought to
hold its voltage a little better than that, unless, of course, the
engine is seized and the starter motor can't turn. So the click
you're hearing is the solenoid, but you don't hear the starter motor
engaging? If that's the case, I'd have a closer look at the battery
and charging system. I'd be somewhat suspicious about the 12V o/c on
the battery.

OK, just for a reference point I went out and measured the battery
voltage on my tractor. Bear in mind, it hasn't run in almost a month,
nor was the battery externally charged. It read 12.78V (and my meter
is accurate to better than .1V) no load, and 10.95V with the starter
motor running.

So, if I were you, I'd put a set of jumper cables from your car to the
tractor and give it another try. From the data you give, the state of
battery charge would be the first thing to look at. Once you get it
running, verify that you're getting at least 13.8V on the battery from
the charging circuitry.