TM 9-4910-582-14&P
During this process if the operator c a r e f u l l y watches the gauge hand, a
s t i c k i n g valve easily may be detected. T h e hand progressively rises with
e a c h revolution of the starting motor until no further rise is obtained. T h e
i n d i c a t e d pressure on the gauge represents the maximum compression
p r e s s u r e under the prevailing conditions.
S h o u l d the hand remain fixed at any one of the "beats" or revolutions of
t h e starting motor and then again rise, the point where it lagged indicates a
v a l v e sticking in the open position. C o m p r e s s i o n pressures will be found to
b e higher in modern engines than for older models.
W i t h the pistons, rings, valves and gaskets in good condition, maximum
r e a d i n g s on all cylinders should be uniform within plus or minus 5 lbs. of
specified pressures.
T h e maximum overall readings will vary slightly according to the altitude, but
are influenced considerably by overall engine temperatures,
oil
viscosity,
cranking
speed, valve settings, etc.
L o w readings on adjacent cylinders will o r d i n a r i l y indicate gasket leakage
between cylinders.
L o w cylinder indication - p a r t i c u l a r l y in one cylinder - indicates either
i m p r o p e r valve seating or piston and ring blow-by.
I n order to re-check, heavy sealing oil may be squirted onto the heads of
a l l of the pistons and a re-check similar to the first test carried out.
P R E V E N T I V E MAINTENANCE. All parts of the equipment should be wiped
c l e a n and dried after use and retained in the carrying case to prevent damage.
TROUBLESHOOTING. Should a pressure drop occur when reading the pressure gage,
p r e s s u r i z e the unit with compressed air; Caution: Do not exceed 300 psi. S u b m e r g e
u n i t in water up to the stem of the Pressure Gage. D O not submerge Pressure Gage.
B u b b l e s will appear at the leak. Tighten as is necessary and repeat test with unit
pressurized.
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