There is a solenoid on the steering column that keeps you from shifting from park unless your foot is on the brake pedal, when the key is in the on position. With the key one click forward of off you can shift from park. That's built in intentionally, in case the stop light switch fails or the stop light fuse fails.
The most common no starter engagement, for you chassis, is the starter relay. It is located in the left side of the dog house, adjacent the throttle pedal.
If you go to
IRV2/Ford Motorhome Chassis and ask for the relay location, "subford" will probably post a pic of the location.
Richard
