Air Driven Liquid Pump 4B Series • OM-16F
8
Troubleshooting Guide
Air Drive Side
Problem
Possible Cause(s)
Action
A. Will not cycle.
No audible air leakage at air
exhaust port.
1. Cycling spool stuck due to
contamination.
2. Low drive pressure
3. Pilot valve stem(s) too short
or reversed.
1. Remove spool from upper
cap (per instructions 4.1 A
thru D). Clean, inspect,
relube and reinstall. Check
drive air filter.
2. Provide 25 psi minimum.
3. Replace or assure that
27375-5 and 27375-3 are in
proper location per
assembly drawing.
B. Will not cycle.
Audible air leakage at air
exhaust port.
1. Drive air volume being
restricted.
2. Drive air o-ring P/N 56225
damaged or undersize (due
to age).
3. Spool o-rings P/N 546285
worn or damaged.
1. Increase air line size.
2. Replace (per instructions 4.2
A thru G).
3. Replace (per instructions 4.1
A thru D).
C. Will not cycle (or short
cycle). Audible air leakage at
pilot vent hold lower cap
casting.
1. Seat of pilot valve 27375-3
damaged or spring 57324
broken.
2. Pilot valve springs reversed.
1. Replace (per instructions 4.3
A, B).
2. Install correctly per
assembly drawing. 57324 is
lighter.
D. False cycling (rapid
“hunting” action). Air
continuously leaks at vent
port in upper air cap. Or
rapid “puffing” of pilot air out
vent hole in hydraulic cap.
1. Pilot air loss past dynamic o-
ring 568115-2 on spool.
2. Pilot valve 27375-5 seat
damaged or 16513 broken.
1. Replace o-ring (4.1 A thru
D)
2. Replace. (4.3 A, B)
Liquid Side
Problem
Possible Cause(s)
Action
E. Liquid blowing out muffler.
1. Damaged or worn plunger
seal.
1. Replace seal. (4.4)
F. Will not stall against blocked
system or will not prime.
1. Inlet check valve damaged.
1. Inspect, repair or remove
contamination. See also 3.1
D.
G. Excessive pulsation or
output pressure.
1. Outlet check valve
damaged.
1. Inspect, repair or remove
contamination. See 4.4 B
and also 3.1 D.
H. Output flow diminishing with
constant conditions.
1. Inlet check valve leakage.
1. Inspect inlet check for
damage or contamination.
Clean & repair. (4.5 A thru
D).