32 Retaining ring
33 Retaining ring
35 Connecting rod assembly
Pump unit subassembly
Figure 3-18. Pump assembly, exploded view -Continued
c. If necessary, rock pump assembly (44)
spring rate scale extension (5) to shoulder pin
slightly while pulling it directly away from chas-
sis assembly (36).
(4) Connect M74 test set PRESSURE
TEST tubing (4) to fluid inlet port (3).
a. Dampen the outside of four ports on top of
(5) Connect bellows and pump to M74 test
pump assembly (44) with water.
set PRESSURE PORT.
(6) Turn M74 test set PRESSURE LOCK
b. Position pump assembly (44) so that its
valve fully counterclockwise.
electrical connector and ports are alined with
(7) Alternately squeeze and release bulb of
Press pump assembly (44) into place in chassis
bellows and pump until M74 test set PRESSURE-
assembly (36). Secure pump assembly in posi-
VACUUM GAGE indicates 10 to 12 inches of
c. Replace detector
unit assembly (1, fig. 316)
(8) Turn PRESSURE LOCK valve fully
in bottom case assembly (2) and secure with
four catches (10).
to spring rate scale extension (5).
(10) Slowly move spring (6) in the direc-
tion of arrow (fig. 3-19) while observing PRES-
(1) Remove pump assembly from detector
(11 ) When pressure begins to decrease, spring
rate scale must indicate 40 to 90 grams.
(2) Remove two screws (26) and lockwash-
(12) If not, spring tension is incorrect. Re-
ers (25) and slide cover (24) from pump unit
subassembly (29 ).
paragraphs b and c below.
(13) Perform M74 test set shutdown proce-
dures (TM 3-6665-260-14).
(1) Slide cover (24) over end of pump unit
subassembly (29 ) until mounting holes are alined.
Make sure that tubing (12 and 15) are in slots in
(1) With cover (24, fig. 3-18) removed, dis-
pump until subassembly (29).
connect end of springs (14) from guide (18).
(2) Install two screws (26) and lockwash-
(2) Disconnect springs (14) from terminal
er (25). Tighten screws.
(3) Install pump assembly in detector unit
(1) Connect replacement springs (14) to
terminal lugs (9).
(2) Connect other ends of springs to guide
(3) Perform spring tension test (a above)
one roller is centered on guide (18) causing
maximum tubing compression.