Troubleshooting the APU Engine Starting System When the Engine Fails
to Crank When Starting Switch is Operated.
Due to locations of APU and APU control box, some troubleshooting
steps will require two persons. In cold weather situations, drain
oil from engine and refill with proper grade of oil (LO 9-2350-267-
For test, APU control panel PREHEAT and STARTER switches must be
Before attempting to perform the troubleshooting procedures which apply to
the APU engine starting system, make the following preliminary checks:
Check batteries for loose terminal connections, low electrolyte
level, low or no charge IAW TM 9-2350-267-20.
require recharging, use the recharging process outlined in TM 9-
6140-200-14. If batteries require replacement, replace IAW TM 9-
Remove the APU access plate IAW TM 9-2350-267-20 and then open
the APU compartment door.
Visually check APU wires and wire connections.
reconnect, or tighten terminals as needed.
If engine still fails to crank after you have performed the preliminary
steps listed above, turn the MASTER switch to the