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Pressure Washer Troubleshooting



Pressure Washer Resource Center


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Component Identification

Pump Repair

FAQ's

Troubleshooting

Service Center

Low Pressure

Cause

A worn nozzle results in lower pressure because there is less resistance to the water flow. A pump generates flow, not pressure. The orifice size of the nozzle determines the resistance to flow and therefore the pressure created. As the nozzle wears the orifice size increases, which produces less resistance. Often, pressure-related problems are not due to the pump, but due to downstream components.

Solution

Replace nozzle with a properly sized nozzle.

View the nozzle selection chart.

Cause

An unloader is a pressure control valve that sets and maintains system pressure. A horizontal internal piston shifts based on downstream pressure to allow flow to either travel to the wand or back to the source through the by-pass port. A worn or “stuck” piston can cause excess bypass flow and low system pressure. 

Solution

Take the unloader apart and inspect the piston valve assembly. Look for evidence of wear and lack of movement. Repair and clean as indicated or replace internal piston.

Cause

Over the course of operation, seal wear occurs due to the reciprocating movement of the plunger. Worn seals allow fluid to migrate to the low-pressure side, which can result in lower flow and thus lower system pressure.

Solution

Inspect and replace seals. Follow service and preventive maintenance recommendations. 

Click here to learn more about repairing your pump.

Cause

The pressure gauge displays the system pressure. Gauges can fail due to over-pressurization or pressure spikes. A faulty gauge reading can lead to misinterpreting system conditions and therefore taking inappropriate actions. Always verify system pressure before attempting system maintenance or repairs. 

Solution

Replace pressure gauge. In some systems, a pressure diagnostics sensing port can be used to verify system pressure. Use high-quality glycerin-filled gauges with built-in pressure snubbers.

Cause

Belt-drives are used to set and control the pump speed, measured in “revolutions-per-minute” or “rpm". Belt slippage causes the pump to run at a slower speed, which affects pump output flow. Lower flow means resistance to the flow decreases, which translates into lower system pressure. Pressure is the resistance to flow. 

Solution

Inspect the belt-drive assembly and belts. Tighten or replace belts as required.

Cause

An inlet filter removes contamination, preventing it from entering the pump. A clogged or improperly sized filter reduces the amount of liquid to the pump inlet, which can cause cavitation and even severe pump damage. Reduced inlet flow results in reduced flow to the system, which works to reduce system pressure as there is less resistance to the lower flow being produced.

Solution

Inspect filter and filter screen or mesh. Clean per instructions. If filter is damaged, replace. Also, verify filter sizing. A good rule-of-thumb is to match the inlet port size of the pump; do not reduce the filter port size.

Cause

Adequate water supply is essential for the operation of the pump. Incoming water lubricates and cools the pump. Water is also required to fill the pump chambers. An inadequate water supply will result in a lower flow being discharged from the pump and therefore lower system pressure. Severely restricting water supply can cause cavitation and lead to catastrophic pump failure, resulting in system shutdown and the need for a complete pump re-build or total replacement.

Solution

Inspect the incoming line for obstructions or any flow restrictions. Follow pump guidelines for inlet port and line sizing. Increase line size if necessary. Verify supply line pressure and increase if indicated.

Water Leak

Cause

The primary function of the seals and o-rings in the pump is to maintain separation between two environments, such as the internal area of the pump housing and the exterior of the pump. A worn seal or o-ring can allow water or the pumped fluid to leak internally or externally, which can be visible as a leak or a drip.

Solution

Inspect and replace worn seals and o-rings. See pump datasheet for internal exploded views that clearly show o-ring and seal replacement ordering information.

Cause

Cracked or crazed plungers can be caused by thermal shock or pressure spikes. A cracked plunger can degrade pump performance, possible affecting flow and pressure. In this condition, a damaged plunger could allow water or the fluid pumped to seep and even pass-through seals, resulting in a leak.

Solution

Inspect and replace cracked plunger(s). Inspect seals also as these may have been damaged by the irregular surface of a cracked plunger.

Oil Leak

Cause

The crankcase has three crankcase oil seals, one on each plunger rod and two crankshaft oil seals. The drive-end crankcase operates in an oil bath (not under pressure) to supply splash lubrication to the drive end components.  Oil seals can wear over time and allow oil to leak. 

Solution

Inspect and replace worn seals. Follow service and preventive maintenance recommendations.

Cause

Pump drive-ends are equipped with either a drain cap or a drain plug.  Drain plugs could work loose due to system vibration, resulting in an oil leak. Other issues could cause oil leaks, such as cross-threading the plug or not applying enough torque to create a tight seal.

Solution

Inspect drain plug for damage. Tighten or replace as indicated.

Cause

Each pump drive end is equipped with an oil sight gauge to view the oil level. A loose or cracked sight gauge could result in an oil leak. Note: it is important to maintain an adequate amount of crankcase oil. Oil level should never fall below the red dot of the sight gauge.

Solution

Inspect and tighten if necessary. Replace if damaged.

Cause

Consult the pump datasheets for the proper volume of oil for a specific pump model. The normal oil volume fills approximately one-half of the pump crankcase. Overfilling the crankcase can result in oil spilling or spurting through the vented filler cap or building internal pressure.

Solution

Reduce oil level to proper volume. Slightly turn filler cap to stop oil from exiting through the oil filler cap vent port.

Pulsation

Cause

Debris and contamination build-up on valve seat surfaces can disrupt the normal flow through the inlet and discharge valves. Debris in either of these valves can allow the water to free flow in and out of that valve chamber and not be properly discharged from the pump. This situation causes irregular flow patterns through the valve chambers, resulting in flow ripple or pulsation.

Solution

Remove each valve or valve stack and inspect. Clean or replace as required. Maintain proper system filtration.

Cause

A pulsation dampener reduces fluctuations in system pressure due to the reciprocating action of the pump plungers or pistons. Most systems tolerate pressure pulsation without any issues, such as pressure washers. A pulsation dampener is commonly referred to as an “accumulator.”  Dampeners may be charged with a gas (such as nitrogen) or spring-loaded. Gas-charged dampeners use a bladder that responds to pressure fluctuations, absorbing pressure spikes.

Solution

Should system pulsation become pronounced, install a dampener. If a pulsation dampener is in use and pulsation is an issue, inspect bladder for rupture, check the dampener’s charge pressure and recharge to factory settings or replace the unit entirely.

Running Rough

Cause

An adequate and smooth (non-turbulent) water supply to the pump is essential for best performance. Turbulent water entering the pump can cause the pump to run very rough.  Conditions that cause turbulent flow include plumbing restrictions such as pipe-reducers and elbows and any source of atmospheric air such as a leak in an inlet hose or a loose connection. Entrapped air can cause “bubbles” that can implode under pressure causing pump cavitation.

Solution

Inspect inlet line for loose fittings, cracked filters, fittings that need to be re-taped or any other restrictions in the inlet line. Use flexible hose if possible and use short-run plumbing to prevent restricted pump inlet flow.

Cause

The high-pressure seals in the pump keep water in the high-pressure chamber.  When one high-pressure seal wears sooner that the other two an uneven flow results that can cause the pump to run very rough.

Solution

Inspect and replace high-pressure seals as a complete set.

Cause

Debris and contamination build-up on valve seat surfaces can disrupt the normal flow through the inlet and discharge valves. Debris in either of these valves can allow the water to free flow in and out of that valve chamber and not be properly discharged from the pump. This situation causes irregular flow patterns through the valve chambers, resulting in the pump “running rough.”

Solution

Remove each valve or valve stack and inspect. Clean or replace as required. Maintain proper system filtration.

Knocking Noise

Cause

Adequate water supply is essential for proper pump performance. A pump uses the incoming water to lubricate and cool its internal components and requires an adequate supply of water to fill the chambers. An inadequate water supply will result in a lower flow being discharged from the pump and can create a loud knocking noise.

Solution

Inspect the incoming line for obstructions; increase line size and/or increase supply line pressure.

Cause

Pump inlet and discharge valves control the flow in and through the pump. Worn valves can allow water to free flow in and out of a valve chamber and not be properly discharged from the pump. This condition can cause a loud knocking noise in the pump.

Solution

Remove each valve or set of valves and inspect for wear or debris. Clean or replace as necessary.

Cause

Air can enter the pump through any openings in the inlet plumbing to the pump. Entrapped air creates bubbles that may implode under pressure, causing caviatation and often loud pump “grinding” noises. Cavitation can wear internal pump components, resulting in possible pump failure.

Solution

Inspect the incoming line for obstructions; increase line size if possible; increase supply line pressure.

Premature Seal Failure

Cause

Water passing through the pump is used to lubricate the seals. Running the pump dry will cause an excessive amount of heat between plungers and the seals, causing them to fail in a short amount of time. Never run a pump dry.

Solution

Always make sure water is getting to the pump before starting the engine. Inspect and replace all worn seals. Inspect the incoming line for obstructions or any flow restrictions.

Cause

Running the pump without washing or spraying water can put the pump into “by-pass mode.” When the pump is in by-pass mode and water is directed back to the pump inlet, excessive heat can quickly build. This is sometimes referred to as “heat rise.” Pump seals can become severely damaged due to high heat. 

Solution

Replace seals and do not run in by-pass mode for longer than 3 to 5 minutes. Add accessories such as a thermal valve or throttle controller to protect pump while it is in by-pass mode.

Cause

Pumps have a maximum operating temperature to protect seals and O-rings from heat damage.  High temperature will cause seals to wear at an accelerated rate.

Solution

Reduce inlet water temperature. If this is not possible, replace seal with high temperature seals that are available as pump options.  Consult the pump datasheet.

Cause

In cases when the inlet water pressure is excessive, the clearance between the seals and plungers can become too restrictive.  The tighter the seals “squeeze” the plungers, the faster the seals will wear.

Solution

Lower inlet pressure with an inlet regulator. In some cases, installing a pressure gauge is recommended to monitor inlet pressure.

Cause

Water with abrasive is very hard on seals and causes the seals to wear quickly.

Solution

Add proper inlet filter to remove abrasives down to an acceptable level.

Cause

Plungers are manufactured with extremely concentric and smooth finishes. Scored or cracked plungers produce an irregular “rough” surface finish that causes seals to wear quickly or unevenly. In extreme cases, seals may tear, resulting in seal failure. 

Solution

Inspect and replace cracked plunger(s). Inspect seals also as these may have been damaged by the irregular surface of a cracked plunger. Plungers may be replaced individually or in complete sets.