GUIDE A. 6D1251 - Caterpillar

Start Relay (Magnetic Switch)
Illustration 1 g00785967The start relay is an on/off solenoid that controls the "starter" motor. When the relay is not energized, the "starter" motor is not running. When the relay is energized, the "starter" motor is running. Relay (Starting Aid)
Illustration 2 g00875516The starting aid relay is an attachment that enhances the starting capability of the engine by adding ether to the fuel mixture during start-up. The starting aid relay is an on/off switch that controls the starting aid valve. When the relay is not energized (0 V), ether aid is not provided. When the relay is energized (12 V), then ether is supplied to the engine.Relay (Lift Pump)
Illustration 3 g00875516The fuel lift pump relay controls the fuel lift pump. When the fuel lift pump relay coil is not energized (0 V), the fuel lift pump does not operate. When the relay coil is energized (12 V), the fuel lift pump operates. When the key switch is in the RUN position, the output for the fuel lift pump relay will energize. The fuel lift pump relay output will turn off when the engine is not running and the run signal for the starter key switch has been on for longer than 60 seconds. The output of fuel lift pump relay will stay energized when the engine is being commanded to start (start relay output is on).or the engine is running. When the key start switch is in the OFF position, the output will not energize the fuel lift pump relay.