(c)  
If you can not get a vacuum of 17 inches of mercury, do the "Leak Repair Procedure".

 S 792-039
 (6)
Close the pump shutoff valve and stop the vacuum pump (Fig 201).

 S 972-067

 (7)  
Make sure the vacuum gage on the hose without the vacuum pump shows the same value as the vacuum gage on the pump with a tolerance of +/- 2 inches.

 (a)  If the two vacuum gages do not show the same value with the applicable tolerance, make sure these valves are open: 1) The crossfeed valve 2) The two engine shutoff valves.
 NOTE: Use the manual override handles on the engine shutoff
____ valves and the crossfeed valve to open them. If one of these valves does not open correctly, refer to AMM 28-22-00/101.
 S 792-040
 (8)  Monitor the vacuum gage for five minutes.
 (a)  If the vacuum pressure decreases one inch of mercury or less for the five minute time, stop this procedure. 1) Do the procedure: "Put the Airplane Back to Its Usual
 Condition".
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 28-22-00
 ALL  ú ú 01 Page 207 ú Nov 12/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
SEE A
VACUUM HOSE FIRE
CONNECTION LEFT SERVICE
EXTINGUISHING SEE BDISCONNECT
PORT (REF)
PANEL

D410 D400
THROTTLE PUSH-PULL
CABLEFWD
STARTER AIR
DUCT (REF)

HYDRAULIC CASE DRAIN FUEL
ENGINE FUEL  LINE (REF) SUPPLY
LEFT SERVICE SUPPLY HOSE  LINE
DISCONNECT
PANEL
VACUUM
HOSE ATTACH AIR SUPPLY (100 psi)VACUUM GAGE
VACUUM HOSE CONNECTION
NOTE: DISCONNECT THE FUEL SUPPLY LINE AND CONNECT THE VACUUM HOSE
B
TO DO THE VACUUM TEST.
Vacumm Test Equipment
Figure 201

B02257
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 ALL  ú ú 03 Page 208 ú Mar 15/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (b)  If the vacuum pressure decreases more than one inch of mercury for the five minute time, do the "Leak Repair Procedure".
 G. Leak Repair Procedure
 S 652-072
 WARNING: OBEY ALL OF THE SAFETY PRECAUTIONS IN THE PURGING AND ENTRY
_______ PROCEDURE. INJURY TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR.
 (1)  
Do this task: "Fuel Tank Purging and Entry" for the center tank (AMM 28-10-00/201).

 S 862-041

 (2)  
Get access to all the fuel tanks.

 S 792-042

 (3)  
Do these steps to examine the fuel feed lines and the couplings for indications of leaks (Fig. 202):

 (a)  
Make sure the vacuum pump is in operation.

 (b)  
Make sure the shutoff valve on the vacuum pump is fully open.

 (c)  
Close the crossfeed valve.

 (d)  
Do the Vacuum Test Procedure again.

 NOTE: This will show which side of the crossfeed valve has
____ the tubing with leaks. You can do this procedure again with each of the engine shutoff valves closed to isolate the leak more exactly.
 (e)  
While the vacuum pump operates, look for a bad coupling or fuel line (AMM 28-22-15/601).

 (f)  
Listen for air leaks at the couplings.

 S 362-043
 (4)  If a coupling has a leak, do these steps to repair it
 (AMM 28-22-15/401):

 (a)  
Disassemble the coupling.

 (b)  
Replace the O-rings.

 (c)  
Assemble the coupling again.

 S 362-044
 (5)  If a fuel line has a leak, replace that fuel line
 (AMM 28-22-15/401).

 NOTE:____Make sure the joints are aligned correctly. Make sure the clamps are installed correctly on the lines that you moved during this task.
 S 792-045
 (6)  Do the "Vacuum Test Procedure" again.
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