Starter diagnostic.

Not necessarily. First thing I would do is use a small jumper wire to jump from the battery cable terminal on the starter solenoid to the small activating terminal of the starter solenoid. IF there are two small terminals on the solenoid, one will be a ground, do not jump to that. IF the starter runs now you know battery, cables and solenoid are good and problem is likely in the safety wiring circuit. IF it doesn't, try below.

Use a good set of jumper cables to jump directly from the battery to the starter terminal using only one side of the cables. IF starter runs, you know the problem is in the wiring, probably safety wiring circuit but could be cable, cable connection, switch, solenoid. Starter doesn't run, connect the other side of jumper set from battery to engine block. IF starter runs now, you have a bad ground connection, cable.

You are sure your battery is good?

Note: 12 volts at solenoid does not mean you have enough amperage.

Walt Conner

If you have the 4 wire solenoid....don't assume the small ground term is definitely grounded to chassis and bat negative, especially if you cannot see such wire.....It may be looped thru the safety switches...You can temporarly jumper the term to ground and see if it will now allow eng to crank...beware you are thus defeating the safety at that time...and only for this test..