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Pressure Washer Pump Troubleshooting

This guide is intended to give our customers a basic idea as to the symptoms and causes of the faults which can occur with pressure washer pumps. Some faults have simple solutions which can get the machine back up and running quickly.

In nearly every case a pressure washer pump fault will be the result of incorrect use or an attempt to fit parts without the necessary know how, but all pumps also have wear parts which do require replacing over a period of time such as the seals. Misuse such as not cooling a hot water machine down before switching the pressure washer off, or leaving a manual pressure washer in bypass mode will both contribute to pump failure which is why we offer training for the use of pressure washers and whenever se sell a machine we always offer to setup the machine on site and take the user through the do’s and don’ts of their new pressure washer.

Pressure Washer Troubleshooting Table

Please find below a brief explanation of some of the faults and their respective solutions, please note that this is just for the pump side of the pressure washer. Always isolate the machine at the electric supply before attempting any repair. I’m afraid we will not be producing a guide for burner faults as this can often involve electrical problems with very high voltage.




Gun and hose vibrates

Debris under pump valves

Valve seat o-rings are damaged

Remove/replace debris of valve from machine

  Sucking air on suction side of pump

Look for leak on suction side

You may need to couple the inlet water supply direct to the pump in order to identify the leak

  Pump Piston is not being driven


Pump requires stripping down and repairing or replacing



  Valve seat O-rings are damaged Remove valves, check o-rings and replace if necessary

Pump runs but no water is emerging from lance

Lance nozzle is blocked Check nozzle, remove the nozzle for cleaning and then replace
  Water starvation Check water supply to the pump and any filters for blockages
  Machine is air locked If machine has high pressure chemical close the tap and bleed the system up without the hose and gun connected

Pump pressure low

Unloader valve is faulty Strip unloader, check for debris or replace unit
  Water starvation Check any water filters for blockages
  Nozzle is worn Remove and replace nozzle
  Pump seals are worn Strip pump and replace seals

Machine pressure surges up and down

Blockage in nozzle Remove nozzle and check for debris, replace if necessary
  Unloader valve is faulty Strip unloader, check for debris or replace unit
  Restriction in post pump line Check for any restriction, machine may need descaling

This is by no means an exhaustive list of problems and if you are in any doubt please contact us in order to arrange a callout or to bring the machine into our workshop for attention.

Alternatively, contact us here for further information.