CONDITION POSSIBLE CAUSE CORRECTION
Oil motor stalls at bottom. Fluid pump piston seat unthreaded. If connecting rod is okay, remove cylinder head plug and pop valve down. Replace plug and start
(No unusual heat problems.) machine. If machine cycles up and stops at bottom again, then problem is piston seat on fluid pump.
Check piston seat. Repair or replace as necessary. If piston seat is okay and problem does not
change,
check oil motor.
Valve sticking or oil motor trip rod shifter Remove valve and check for scratches and rough movement when sliding it up and down. Replace
assembly separated. valve and spool in this condition. Check trip rod for possible separation.
and spool in this condition. Check trip rod for possible separation.
Oil motor stalls at top. Valve sticking. Remove valve and check for scratches and rough movement when sliding it up and down. Replace
(No unsual heat problems) valve and spool in this condition.
Broken spring retainer (valve rod Replace valve rod assembly.
assembly)
Broken spring or valve rod. Replace valve rod assembly.
Air in hydraulic motor. Reset Valve.
Purge Air, generally accomplished by low pressure cycling of moter/pump assembly for 5 - 10 minutes.
Check for causes of air introduction.
• Loose fittings in tank.
• Loose fittings on hydraulic pump.
• Loose hose connections.
• Low oil in reservoir.
Air in fluid pump. Stall at top can occur randomly when fluid pump picks up air. Reset valve. Avoid air in the fluid pump.
Low pressure (okay on Blown piston seal. Before dismantling oil motor, start machine. With pump cycling under pressure, touch the hydraulic
down stroke, sluggish on cylinder and the head to see if cylinder or head gets hotter. This will help determine if piston seal.
up.stroke - high heat) is blown or piston nut is broken. If heat is on the head, check the O-Rings on spool valve.
Note: Engine labors on
upstroke, idles back at stall
on the down stroke.
Cracked piston. Dismantle oil motor and check piston seals cylinder bore and piston nut. Pay special attention to piston
nut. It can be cracked and not show externally.
Low pressure (both strokes Blown center O-Rings on spool valve. Before dismantling oil motor, start machine. With pump cycling under pressure, touch the head to see if
- high heat) the head becomes hotter. This will help determine if center O-Ring is blown on spool valve. If hot,
Note: Engine labors at stall remove and replace O-Ring.
on both strokes
Bad hydraulic pump. Replace hydraulic pump.
TROUBLESHOOTING GUIDE HYDRAULIC MOTORS
15
TROUBLESHOOTING GUIDE FLUID SECTIONS
CONDITION POSSIBLE CAUSE CORRECTION
Pump delivers on upstroke only or Lower foot valve ball is not seating due to Remove foot valve assembly. Clean and inspect. Test foot valve by filling with
goes up slowly and down fast. trash or wear. water; if ball fails to seal the seat, replace ball.
(Commonly called downstroke dive.)
Material too viscous to syphon. Thin material - contact manufacturer for proper thinning procedures.
Air leaking in on syphon side or damaged syphon Tighten all connections between pump and paint container. If damaged, replace.
hose. Syphon may be too small for heavy material Switch to larger diameter syphon set.
Pump delivers on down stroke only Upper ball is not seating due to trash or wear. Check upper seat and ball with water. If ball fails to seal seat, replace.
.or goes up fast and down slowly
Lower packing set is worn. Replace packing set if worn.
Pump moves up and down fast, Material container is empty or material is too thick Refill with new material. If too thick, remove syphon hose and immerse pump or not
delivering material. to flow through syphon hose add thinner to material. Change to bigger syphonset. Open bleed valve to .
remove air and restart pump.
Bottom ball stuck to foot valve seat. Remove foot valve. Clean ball and seat.
Syphon hose is kinked or loose. Straighten.
Pump moves up and down slowly Loose connections. Bleed valve is open partially or Check all connections between pump and gun. Tighten as necessary. If material
when spray gun is shut off. bleed valve is worn. Lower packing seat is worn. is flowing from bleed hose, close bleed valve or replace if necessary. Should
none of the above be evident, replace lower packing.
Upper and/or lower ball not seating. Reseat balls by cleaning.
Not enough fluid pressure at gun. Spray tip is worn. Replace.
Outlet filter or gun filter is clogged Clean or replace filter.
Low voltage and/or inadequate amprage. Check electrical service. Correct as required.
Hose size or length is too small or too long. Increase hose size to minimize pressure drop through hose and/or reduce hose
length.
Pump chatters on up or down stroke Solvent has caused upper packing to swell. Replace packing.
