Engine Overload Protection System

Fig. 55 Engine Overload Protection System Wiring Diagram:

NOTE: See Fig. 55 for a wiring diagram.

1. Check the boost pressure lines for leaks. Disconnect the boost pressure line to switchover valve at intake manifold and connect pressure tester to the boost pressure line. Turn preglow/starter switch to the off position and apply 800 to 900 mbar pressure. If the pressure drops more than 50 mbar in one minute, check individual boost pressure lines, switchover valves and vacuum amplifier for leaks. Replace parts as required. If the pressure does not drop more than 50 mbar in one minute, proceed to step 2.
2. Turn preglow/starter switch to the second position. Move throttle linkage to a part throttle position. The switchover valve should switch audibly. If the switchover valve can be heard, proceed with step 5. If the switchover valve cannot be heard, proceed with step 3.
3. Disconnect plug from switchover valve and check voltage between terminal 2 of plug and ground. If 12 volts is read, proceed to step 4. If 12 volts is not read, check for and repair any open circuits.
4. Check voltage on switchover valve plug between terminal 1 (-) and 2 (+). If 12 volts is read, replace the switchover valve. If 12 volts is not read, check for and repair any open circuits. Replace the microswitch as needed.
5. With the throttle at a part throttle position, momentarily disconnect the pressure switch plug. If the switchover plug does not operate, the system tests good and the test is over. If the switchover valve operates, replace the engine overload switch.