The injection pump found in your 1st generation Cummins truck uses a 12-volt electric fuel shutoff solenoid that turns off the engine when the key is swtiched to the off position. Overtime, this solenoid can become stuck in the off postions not allowing you to start your truck. Replace your failed solenoid with this genuine Bosch Replacement Fuel Shutoff Solenoid and get your truck back on the road.