BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38648
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 1 (BLOCK 1)

YES
NO

10 DO THE FLOW CHECK OF THE FUEL SUPPLY SYSTEM TO THE APU

(AMM 49-31-00/501).
IS THE FUEL FLOW SUFFICIENT?

AND CLEAN THE HIGH-PRESSURE FUEL FILTER (AMM 49-31-81/301).
DOES THE PROBLEM CONTINUE?

YES
SEE SHEET 6 (BLOCK 31)
Starter Motor Turns the APU Engine but There Is No Combustion (No Increase in EGT)
Figure 113A (Sheet 5)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 165
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38650
////////////////////////
A / GTCP85-129 SERIES /
737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 5
(BLOCK 30)
YES
NO

31 DISCONNECT CONNECTOR 72 REPAIR THE CIRCUIT FROM
D1264, FROM THE FUEL SOLENOID  THE FUEL SOLENOID VALVE, 
VALVE.  CONNECTOR D1264, PIN B, TO THE 
MOVE THE APU MASTER SWITCH  SEQUENCING SWITCH FOR THE OIL 
TO THE "START" POSITION.  PRESSURE, CONNECTOR D1250, 
AFTER THE AIR INLET DOOR  PIN 4 (WDM 49-31-01). 
OPENS, DO A CHECK FOR VOLTAGE 
AT THE FUEL SOLENOID VALVE, 
CONNECTOR D1264, PIN B 
(WDM 49-31-01). 
IS THERE MORE THAN 11V DC 
AT PIN B? 

REPLACE THE FUEL CONTROL UNIT (AMM 49-31-11/401).
Starter Motor Turns the APU Engine but There Is No Combustion (No Increase in EGT) Figure 113A (Sheet 6)
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú ú 02 Page 166 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38651
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 5 (BLOCK 12) NO
YES34 WARNINGDO NOT OPERATE THE APU WITH

THE LOWER SHROUD REMOVED IF PERSONS ARE IN OR DIRECTLY BELOW THE APU COMPARTMENT. YOU MUST BE A MINIMUM OF 3 FEET AWAY FROM THE OUTER EDGE OF THE APU COMPARTMENT OPENING TO OPERATE THE APU WITH THE LOWER SHROUD REMOVED. AN APU TURBINE WHEEL SEPARATION DURING OPERATION CAN CAUSE INJURY TO PERSONS.
DO A CHECK OF THE FUEL LINE BETWEEN THE FUEL CONTROLUNIT AND THE FUEL ATOMIZER ON THE COMBUSTER UNIT.
IS THERE ANY DAMAGE?

NO NO

35 REPLACE THE LOW-PRESSURE
FUEL FILTER (AMM 49-31-21/401)
AND CLEAN THE HIGH-PRESSURE
FUEL FILTER
(AMM 49-31-81/301).

DOES THE PROBLEM CONTINUE?

YES
NO
36 EXAMINE THE CIRCUIT FROM THE FUEL SOLENOID VALVE, CONNECTOR D1264, PIN B, TO THE SEQUENCING SWITCH FOR THE OIL PRESSURE, CONNECTOR D1250, PIN 4 (WDM 49-31-01).
IS THE CIRCUIT OK?

YES
SEE SHEET 8 (BLOCK 37)
Starter Motor Turns the APU Engine but There Is No Combustion (No Increase in EGT)
Figure 113A (Sheet 7)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 167
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38652
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 7 (BLOCK 36)

YES
NO

37 MEASURE THE RESISTANCE AT
THE FUEL SOLENOID VALVE,
CONNECTOR D1264, FROM PIN A

TO PIN B (WDM 49-31-01).
　
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