Figure 4-6. Auxiliary power unit test run outside vehicle(Sheet 2 of 2).(c) Start the auxiliarythree-minute warmup periodengine and allow awith no load on theTM 9-2350-256-34-1generator or pump. Then check the engine speedwith a hand tachometer or stroboscope. Adjust to2000 ± 100 rpm, if necessary, in the following man-ner.1. Locate the governor speed adjustmentscrew on the front of the engine (3, fig. 4-1).2. Loosen locknut and turn screw slowlyuntil tachometer or stroboscope reads 2000 ± 100rpm.3. Carefully tighten locknut so that thetachometer or stroboscope reading does not change.(d) Stop engine, check crankcase oil and fill toproper level (LO 9-2350-256-12) if required.(e) Install a pressure gage in the gage port ofthe system selector valve on the hydraulic controlpanel (subplate) assembly (View A, fig. 2-29).(f) Start the auxiliary engine, place themanual shutoff valve in NORMAL OPERATIONposition, place the system selector valve inAUXILIARY position. Check the pressure gage toconfirm a hydraulic load on the auxiliary pump of2000 ± 50 psi. Adjust the system selector valverelief valve with the adjusting screw (View A, fig.2-29), if necessary, to obtain a pressure reading of2000 ± 50 psi.(g) Operate the auxiliary engine for 10minutes with a 2000 ± 50 psi load on the auxiliaryhydraulic pump and no load on the generator.(h) Check all points for leakage (TM9-2305-256-20) and correct any other defects.Return the system selector valve position to theMAIN position and shut off engine.(i) Connect a multimeter between thegenerator armature terminal and ground (set meteron DC voltage mode—50 volt range).(j) DELTED(k) DELETED(l) Turn on the generator switch momentarilyand note the generator output voltage on themultimeter. Voltage should increase slightly whenthe generator switch is turned on. If not, remove thecap from the switching relay box assembly in thevehicle. Loosen the rheostat locking nut and turnthe adjusting screw slowly clockwise until thevoltage on the multimeter increases slightly. Ifvoltage does not increase, troubleshoot the system.INOTECurrent limiter rheostat must becalibrated when the auxiliary power unitis reinstalled in the vehicle.(m) Turn off generator.(n) Turn off engine.(3) Test inside vehicle.(a) Make sure that all lines, cables, ac-cessories and other components are properly in-stalled, tightened and adjusted. Fill chain case andcrankcase to the proper levels (LO 9-2350-256-12)if required.Change 24-20.3
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