My 02 Isuzu Rodeo wouldn't start. Turn the key on, it clicks one time, then nothing. I'm thinking starter solenoid, which I'm told is actually mounted on the starter. But, there is a cylinder shaped solenoid (?) mounted to a triangular shaped housing (about 3 inches) attached to the firewall. I tapped on that solenoid several times and the starter engaged and started. What is that solenoid (on the firewall)? Should I replace the starter.. or what?