TM 9-4910-701-14&P
TROUBLESHOOTING AND REPAIR
I.
JACK WILL NOT LIFT OR RAISE LOAD
Be sure release valve is closed.
1.
Sometimes hydraulic jacks become airbound.
To correct, place front
2.
wheels on 3" block, open the release valve and pump handle eight full
90 strokes.
refilling
instructions
Your jack may be low on oil.
3.
See
The pump valves may be held open by a foreign particle.
4.
To flush
valves, open release valve partially (about 1/2 turn of knob), and
pump handle several strokes.
If this does not clear them, remove the
oil filler screw in reservoir to relieve any pressure. Be sure
release valve is open. Refer to illustrations on parts page to
identify pump valves.
Remove pump valves for a thorough cleaning.
Also inspect and clean seats.
When replacing valves, insert a new
No. 11520 Seal, using Seal Tool SS-12 for this purpose.
5.
Pump Piston
V packings may be worn.
If S O , oil will leak around
To inspect, remove hydraulic unit as follows.
one or both pistons.
First, remove pins to disconnect both piston links from handle
fork.
Loosen Allen set screws holding handle pins and slide pins
outward sufficiently to remove release hanger, release extension
Remove screw and clip
rod and tension spring from release collar.
from end of ram, and take out unit.
Pull out pistons, keeping piston end of unit up so oil is not lost.
If worn, dip new V
Remove packing nuts and inspect "V" packings.
packings in oil and insert hard ring with flat side down, followed
by soft rings with grooved side down, being careful not to damage
Turn down packing nuts sufficiently to
lips on machined threads.
Dip pistons in oil and insert.
hold "V" packings in position.
Tighten packing nuts to medium pressure.
6.
The Release Valve may be held off its seat by a foreign particle.
Flush by opening release valve and pumping handle several full
If necessary to clean or inspect release valve, first
strokes.
Place unit
remove hydraulic unit as described in Instruction 5 .
in vise with release valve end up and jaws of vise resting on unit
Take out oil level screw at top of unit casting to re-
casting.
Turn out release valve by the
lieve any pressure in the unit.
large hex packing nut.
Clean and inspect release seat and tip of
release screw.
A slight ring on tip of screw is not harmful. A
nicked screw should be replaced.
II.
IF JACK LOWERS UNDER LOAD
1.
The release valve and seat should be flushed and inspected as
described in Instruction 6 of Section 1.
3
