SECTION V: TROUBLESHOOTlNGTM 9-2350-256-20JKLMNOPQRCheck PREHEAT switch on APU control box formalfunction by troubleshooting APU starter circuit,Check for clogged fuel lines. Clean or replace lines(see paragraph 13-5).Check for dirty fuel filters. Clean or replace filters asnecessary (see paragraph 13-5).Remove APU access cover (see paragraph 9-49).Check that all air intake tubes and passages are freeof obstructions. Remove obstructions from airintake tubes and passages.Check high engine temperature sending unit.Troubleshoot APU high air temperature circuit (seeparagraph 2-19, APU HIGH AIR TEMP lamp doesnot light when air temperature is high). If defective,notify Direct Support Maintenance.Check for air in fuel supply system. Bleed fuel linesat fuel filters (see paragraph 13-5).Remove APU access cover (see paragraph 9-39).Check fuel for contamination. If contaminated fueli s f o u n d , d r a i n f u e l t a n k s a n d f i l l w i t huncontaminated fuel (refer to TM 9-2350-256-10).Check air intake tubes for restrictions. If restrictionsare found, clean or replace tubes (see paragraph13-2).Notify Direct Support Maintenance.MAIN HYDRAULIC PUMPSYMPTOMSMain hydraulic pump fails tooperate.Do steps A through E.Main hydraulic pump fails toMain hydraulic pump is noisydevelop sufficient pressure.during operation.Do steps C through F.Do steps C through F.AEnsure system selector control lever is in the MAINposition. If problem persists, go to step B.BTest for defective power control valve or restrictedhose.Remove hose No. 66 from mechanicaltransmission (see paragraph 12-1). With mechanicaltransmission drive shaft rotating, and power controlvalve lever placed in ON position, oil should flowfrom hose.2 - 5 3
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