When the fuel solenoid plunger fails to function properly, a voltage check
at fuel solenoid 421 lead terminal must be made. Place the red multimeter
probe on 421 terminal and ground the black probe. Set the MASTER switch and
the FUEL SHUT OFF switch to the ON position. If voltage is indicated during
this test, the fuel solenoid is defective and you must notify Support
Maintenance. Refer to Figure 13 when performing this test.
APU Electrical Diagram.
Fuel Solenoid Plunger and Lead Terminal 421.