The Haynes Diesel Techbook #10330 also shows only one solenoid for your model, mounted on the starter motor. To check the solenoid, connect a jumper wire between the battery (+) and the ignition switch wire terminal (the small terminal) on the solenoid. If the starter turns over, the solenoid is OK and the problem is in the ignition switch, neutral start switch, or the wiring. (Make sure the parking brake is set, the wheels blocked, and the tranny is in neutral or park before doing this!) Is yours auto or manual? The tranny neutral start switch or the clutch safety switch cause lots of starting problems.