OPERATING THE AUXILIARY POWER UNIT (APU)

TM 5-4210-233-14&P-1

2-16. OPERATING THE AUXILIARY POWER UNIT (APU)

a. Bleed Fuel System (Initial Start-Up).

(1) Remove the fuel return line located in floor of APU

compartment. Place the fuel return line in a suitable

container.

(2) Operate the priming lever on the fuel transfer pump

until bubbles cease to appear in the fuel.

(3) Connect the fuel return line.

NOTE

If the fuel pump lobe on the camshaft is up, crank

the engine one revolution to permit hand priming.

When finished, return the priming lever to the

disengaged (inward) position.

b. Starting. Check the engine to make sure the fuel system has

been bled and it has been filled with oil. if necessary, prime

the fuel system as described above.

(1) When starting a cold engine in ambient temperatures

above 55 , preheat with GENERATOR PREHEAT

switch for 20 seconds.

NOTE

Low temperatures may require longer preheating. If

engine fails to start quickly, allow 30 seconds for

starter to cool. Apply preheat for 1 minute, and

repeat starting procedures.

(2) Continue to hold GEN. PREHEAT switch.

(3) Press the GENERATOR START/STOP switch to

start position.

(4) Release the GENERATOR START/STOP switch

after the engine starts and reaches speed.

CAUTION

If oil pressure does not reach operating pressure,

stop engine immediately and troubleshoot. Failure

to heed this caution can result in damage to APU

engine.

(5) Check oil pressure on gauge mounted on APU. Oil

pressure should read approximately 20 psi.

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