In nearly all instances, pressure washer pump failure is the result of improper installation or operation rather than normal wear. One of the most common causes of pump failure is improper or unnecessary service, often as a result of the operator attempting the service.

Each time the pressure pump is serviced, the chance of pump failure as a result of improper service increases. The operator should be left with no reason or desire to open the pump for service.

Usually requests for service are not made until the operation of the equipment has become so bad that it usually does not work.

"The high pressure pump is generally one of the most dependable and best constructed components in a high pressure cleaner. The well-engineered pump may be installed in a not-so-well engineered system." All pumps have wear parts, which eventually need to be replaced.

"In most cases, the high pressure pump is likely to outlast most other components as long as the pump is installed correctly and the system is operated properly." (This is a quote from The Universal Guide to High Pressure and Steam Cleaner Repair

 

Problem	Probable Cause	Solution
Oil Leak Between Crankcase and Pumping Section	Worn crankcase piston rod seals.	Replace crankcase piston rod seals.
	O-rings on plunger retainer worn.	Replace o-rings.
Frequent or Premature Failure Of the Packing	Scored, damaged or worn plunger.	Replace plungers.
	Overpressure to inlet manifold.	Reduce inlet pressure.
	Abrasive material in the fluid being pumped.	Install proper filtration on pump inlet plumbing.
	Excessive pressure and/or temperature of fluid being pumped.	Check pressures and fluid inlet temperature; be sure they are within specified range.
	Over pressure of pumps.	Reduce pressure.
	Ran without water.	Do not run pump without water.
Pump Runs but Produces no Flow	Pump is not primed.	Flood suction then restart pump.
Pump Fails to Prime	Air is trapped inside pump.	Disconnect discharge hose from pump. Flood suction hose, restart pump and run pump until all air has been evacuated.
Pump Loses Prime, Chattering Noise, Pressure Thread Fluctuates	Air leak in suction hose or inlet fittings.	Remove suction line and inspect it for a loose liner or debris lodged in hose. Avoid all unnecessary bends. Do not kink hose.
	Clogged suction strainer.	Clean strainer.
Low Pressure at Nozzle	Unloader valve is bypassing.	Make sure unloader is adjusted properly and bypass seat is not leaking.
	Incorrect or worn nozzle.	Make sure nozzle is matched to the flow and pressure of the pump. If the nozzle is worn, replace.
	Restricted intake.	Refer to above priming information.
Pump is Noisy	Pump sucking air.	Check suction manifold.
Pressure Gauge Fluctuates	Valves worn or blocked by foreign bodies.	Clean or replace valves.
	Packing worn.	Replace packing.
	Pumped liquid temperature too high.	Reduce temperature of pumped liquid.
Over Pressure When Gun is Closed .	Leaking in unloader valve and incorrect setting.	Control the valve and set new pressure level.
Pulsation	Faulty pulsation damper.	Check pre-charge; if low, recharge it or install a new one.
Low Pressure	Worn nozzle.	Replace with nozzle of proper size.
	Belt slippage.	Tighten or replace with correct belt.
	Air leak in inlet plumbing.	Disassemble, reseal and reassemble.
	Relief valve stuck, partially plugged or improperly adjusted valve seat worn.	Clean and adjust relief valve; check for worn or dirty valve seats. Kit available.
	Inlet suction strainer clogged or improperly sized.	Clean. Use adequate size. Check more frequently.
	Worn Packing. Abrasives in pumped in cavitation. Inadequate water.	Install proper filter. Suction at inlet manifold must be limited to lifting less than 20 feet of water or 8.5 psi vacuum.
	Fouled or dirty inlet or discharge valves.	Clean inlet and discharge valve assemblies.
	Worn inlet, discharge valve blocked or dirty.	Replace worn valves, valve seats and/or discharge hose.
	Leak in the discharge line.	Repair leak.
Pump Runs Extremely Rough, Pressure Very Low	Restricted inlet or air entering the inlet plumbing. Proper size inlet plumbing;	Check for air tight seal.
	Inlet restrictions and/or air leaks. Stuck inlet or discharge valve.	Clean out foreign material. Replace worn valves. Replace worn cup or cups.
Water Leakage From Under Manifold. Slight Leakage	Worn packing.	Install new packing.
Oil Leaking in the Area of Crankshaft	Worn crankshaft seal or improperly installed oil seal o-ring.	Remove oil seal retainer and replace damaged o-ring and/or seals.
	Bad bearing.	Replace bearing.
Excessive Play in the End of the Crankshaft Pulley	Worn main bearing from excessive tension on drive belt.	Replace crankcase bearing and/or tension drive belt.
Water in Crankcase	Humid air condensing into water inside the crankcase.	Change oil intervals. Use any high grade automotive 30 weight non-detergent oil.
	Worn packing and/or piston rod sleeve, o-rings on plunger retainer worn.	Replace o-rings. Replace packing.
Oil Leaking from Underside of Crankcase	Worn crankcase piston rod seals.	Replace seals.
Oil Leaking at the Rear Portion of the Crankcase	Worn crankcase piston rod seals.	Replace seals.
Loud Knocking Noise in Pump	Pulley loose on crankshaft.	Check key and tighten set screw.
	Broken or worn bearing.	Replace bearing.