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Solo Backpack Sprayer Troubleshooting Guide
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Difficulty in moving pump lever
Dirty bushing
Remove pump lever, clean & grease bushings
Dirty cylinder walls (425)
Remove piston, clean/replace piston & collar
Collar swollen from long term exposure (425)
Replace collar and maintain according to instructions
Lack of lubrication (425)
Lubricate Viton collar
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Insufficient resistance during repeated pumping and no pressure
Damaged/dirty valve plates
Clean or replace valve plates or cylinder
Damaged O-ring at valve seat
Replace O-ring 
Collar or piston (425) worn
Replace collar or piston
Seal in pressure regulator is leaking
Check seal and valve seat
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High resistance after just a few pumping strokes, pressure lasts only briefly
Little or no air cushion in pressure cylinder
Remove PVC hose, drain pressure cylinder, Reconnect hose. Preventive measure - release pressure after each use
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During spraying, upward pumping becomes more & more difficult and tank walls may indent upwards
Wrong formula tank cap (no vent hole)
Replace with vented cap
Vent hole clogged
Clean vent hole.
Lower valve plate sticks
Replace valve plate
Intake channels clogged
Clean channels & tank
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When handle is pulled up it wants to move itself forcibly back down
Inlet screen at base of pressure cylinder clogged
Clean intake screen with a small brush and detergent
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Leaks inside cylinder (425)
Damaged/dirty collar or piston
Clean or replace collar and possibly cylinder if worn
Leaks outside cylinder (425)
Damaged O-ring on cylinder

Damaged O-ring on pressure cylinder
Replace O-ring

Replace O-ring
Leaks from diaphragm pump  (474, 475, 476, 485)
Damaged diaphragm

Damaged O-ring on diaphragm housing

Damaged O-ring on pressure cylinder
Replace diaphragm

Replace O-ring

Replace O-ring
Leaks from end of spray wand
Worn or damaged shut-off valve
Inspect and rebuild shut-off valve 

Note: Always wear rubber gloves, safety goggles and appropriate protective clothing when repairing a sprayer. Work in well ventilated area. Prior to repair, flush unit with water by filling, then spraying the water into an appropriate container or area. Ensure that all pressure is released by locking the shut-off valve in the open position. Once a repair is completed, fill the unit with clean water, pressurize, and check for leaks. If the sprayer leaks, Do Not Use. Repair leaks and recheck.

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