(f)
Disconnect fuel supply line at fuel atomizer assembly.
(g)
Connect test pressure gage (component of gage and case set) to fuel supply line.
(h)
Close the fuel system boost pump circuit breakers.
(i)
Position BATTERY switch to ON and remove placard.
501
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C76308
Fuel Control Unit Adjustments 519
49-21-01 Figure 503 Oct 20/93
Page 512
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(3) Test fuel control unit acceleration limiter valve cracking pressure.
(a)
Position APU master switch to START and release.
NOTE: APU master switch will return to ON. Engine motoring will begin after air inlet door and APU fuel valve have opened. Make sure the fuel boost pump is operating. After approxinately 90 seconds of motoring, motoring is terminated by a time limiting device in APU control unit.
(b)
While engine is motoring, loosen fuel line nut at pressure test gage (component of gage and case set) and bleed trapped air from line and tighten nut.
(c)
As engine rpm stabilizes, observe acceleration limiter valve cracking pressure. Cracking pressure should be 60 + 3 psig.
(d)
FUEL CONTROL UNIT WITHOUT THE TIMED ACCELERATION CONTROL; if the cracking pressure is not in the limits, adjust the acceleration limiter valve as follows: 1) Remove the lockwire from the locknut for the valve adjustment screw. 2) Loosen the locknut for the valve adjustment screw. 3) If the cracking pressure is too low, turn the valve adjustment screw clockwise. 4) If the cracking pressure is too high, turn the valve adjustment screw
counterclockwise.
NOTE: A full turn of the adjustment screw is the same as approximately 8 - 10 psig change
5) Tighten the locknut for the valve adjustment screw.
6) Install a lockwire on the locknut for the valve adjustment screw.
(e)
FUEL CONTROL UNIT WITH THE TIMED ACCELERATION CONTROL; If the cracking pressure is more than 65 psig (448 kPa), or less than 55 psig (380 kPa), replace the timed acceleration fuel control unit (AMM 49-31-11/401).
(f)
FUEL CONTROL UNIT WITH THE TIMED ACCELERATION CONTROL;If the cracking pressure is between 55 psig (380 kPa) and 57 psig (396 kPa) or 63 psig (434 kPa) and 65 psig (448 kPa), adjust the adjustment screw on the acceleration limiter valve as follows: 1) Remove the lockwire from the locknut for the valve adjustment screw. 2) Loosen the locknut for the valve adjustment screw. 3) If the cracking pressure is too low, turn the valve adjustment screw clockwise. 4) If the cracking pressure is too high, turn the valve adjustment screw
counterclockwise.
NOTE: A full turn of the adjustment screw is the same as approximately 8 - 10 psig change
5) Tighten the locknut for the valve adjustment screw.
6) Install a lockwire on the locknut for the valve adjustment screw.
(g)
Position APU master switch to OFF.
(h)
After air inlet door has closed, repeat steps (a) and (c) thru (g) until acceleration limiter valve adjustment is satisfactory.
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CAUTION: MAKE SURE YOU OBEY THE DUTY CYCLE FOR THE STARTER MOTOR (AMM 49-11-0/201). DAMAGE TO THE STARTER MOTOR CAN OCCUR.
(4) Restore airplane to normal configuration (Fig. 503)
(a)
Position BATTERY switch to OFF and placard.
(b)
Open the fuel boost pumps circuit breakers.
(c)
Disconnect test pressure gage from high pressure fuel line.
(d)
Connect high pressure fuel line at fuel atomizer assembly.
(e)
Install cap on control air pressure port on fuel control unit.
(f)
Position lower shroud against upper shroud and close shroud latches.
CAUTION: MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD.
EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
(g)
Disengage APU compartment access door support rods and stow rods. Close and latch access door.
(h)
Remove placard from BATTERY switch.
(i)
Activate fuel boost pumps as required.
D. Bleed Air Valve Opening Rate Test
NOTE: It is not necessary to do the opening rate test for the bleed air valve after you replace the APU, fuel control unit or bleed air valve. You can use this test for troubleshooting or adjustment of the bleed air valve.
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