If there is insufficient
vacuum or pressure for maximum indications on the
test set instruments, it is necessary to determine
whether the pump is at fault or a leak exists in the
lines. To check the pump, disconnect the pump lines
horn the vacuum and pressure fuel filter sumps and
connect these lines to the altimeter and fuel pressure
instruments respectively. Refer to figure 3-1 for the
vacuum and pressure lines schematic diagram. Turn
on the motor and check that 29 inches of vacuum is pro-
duced on the vacuum side of the pump and that a min-
imum of 25 pounds of pressure is produced on the pres-
sure side. If the pump produces insufficient vacuum for
pressure, the pump is defective and should be replaced.
If the pump is capable of proper operation then a leak
exists elsewhere in the tast set. All fittings, gaskets,
lines, and components should be checked for leaks and
defective components replaced. In replacing a check
valve, be sure to orient replacement valve with arrow
pointing in same direction as arrow on original valve.
Faults in the electrical system can be found by per-
forming a point-to-point wiring check. Refer to figure 2-
5 for the schematic and wiring diagram on the test set.
2-41. Rate-of-Climb Indicator
(1) Disconnect hose assembly from fitting on
rate-of-climb indicator (as instructed in paragraph 244.
(2) Remove the four nuts, Iockwashers, and
screws securing rate-of-climb indicator to front panel.
Remove rate-of-climb indicator.
(3) Remove 45° elbow from rate-of-climb in-
(1) Install 45° elbow on rate-of-climb indica-
(2) Place indicator in position on front panel
and secure with the four screws, lockwashers, and
(3) Connect hose assembly to fitting on rate-
Remove the altimeter in a man-
ner similar to the way the rate-of-climb indicator is re-
Install the altimeter in a
manner similar to the way the rate-of-climb indicator is
installed (para. 2-41).
2-43. Airspeed Indicator
Remove the airspeed indicator in
a manner similar to the rate-of-climb indicator is re-
Install the airspeed indicator
in a manner similar to the way the rate-of-climb indica-
tor is installed (para. 2-45).
2-46. Chassis Assembly
It is necessary to remove the
chassis assembIy from the tester case in the following
manner in order to replace components that are on the
(1) Disconnect all hose and tube assemblies
which are connected to components that are mounted
on the chassis.
(2) Unsolder electrical leads that are con-
nected to fuseholder and light base. Identify leads to fa-
(3) Remove mounting nut securing power
switch tocase and remove switch.
(4) Remove six screws securing chassis as-
sembly to tester case.
(1) Place assembled chassis in position in
tester case and secure with the six screws.
(2) Solder leads on fuseholder and light base
as previously identified.
(3) Place power switch in position on tester
case and secure viith mounting nut.
(4) Connect all hose assemblies to the com-
ponents that are mounted on the chassis.
(5) Position wiring harness on tester case
and secure with screws, lockwashers, and nuts.
2-47. Pressure and Vacuum Filter Sumps.
Remove and disassemble the pressure and vacuum fil-
ter sumps for cleaning and repair, as follows
a. Removal and Disassembly.
(1) Remove tube assemblies.
(2) Remove clamp, bowl, gasket, and filter
from filter sump bodies.
(3) Remove sump bodies and remove elbows