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Servicing and Pump Pressure Issues


ü If You haven’t Used Your Pressure Washer For Extended Period.

ü Checking High Pressure Hose Connections

ü How To Recognize Pressure Loss In Your Pump (Pump Leaking)

ü Low Pump Pressure

ü Sudden Loss Of Pressure – Pump NOT Leaking

ü Gradual Loss Of Pressure – Pump NOT Leaking

ü Effects Of Constant Heat

ü Servicing Pressure Washer Pumps

ü New Or Old Pressure Washer Engine Won’t Start

ü Servicing Pressure Washer Engines

If You Haven’t Used Your Pressure Washer For Extended Period

Pressure Washers that have not been used for months at a time will require the pump to be flushed out prior to starting.

Best way to achieve this is

1. Connect your garden hose & turn the mains water tap on. Do this prior to connecting the high pressure hose

2. Check engine & pump oil levels & for any loose parts

3. Start engine, let the water flow directly out of your pump for approx. 30 seconds.

This will flush any build up of mould & contaminants that build up from water laying in your pump manifold that could have gone stagnant.

If this is NOT done it is highly likely that you will get a blocked jet or nozzle & wonder why there is no pressure!

Checking High Pressure Hose Connections

1. Check the hose connections to pump & gun.

i) Screw Fittings have an o Ring on the spiget of your HP Hose fitting.

If there is a leak, it usually will be the O Rings & will need replacing.

ii) Quick Connect Couplers have an O Ring inside the female part of the pump & hose fitting. The O Ring can blow out under pressure & perish over time so may need replacing if fitting is leaking.

How To Recognize Pressure Loss In Your Pump - (Pump Leaking)

If your pump is leaking water between the main housing & the pump manifold, the piston seal kit has been damaged & needs to be replaced.

If your pump is leaking from around the Check Valve Plugs - replace the O Ring Seals to the plugs.


Heat / Over Pressurized / Pump Running Without Water Flowing Thru / Wear & Tear Pump Pressure

This can result from:

1. Normal wear and tear.

2. Poor water quality.

3. Heat build up in the pump.

4. Not changing oil in Dump Housing.

5. Letting machine run on without trigger being pulled.

A pumps life expectancy depends on how you operate your pressure washer, manage heat build up in your pump & change oil in the crank case housing.

Most Pressure Washers have a Pressure Activated Unloader Valve.

When you let go of the trigger, the unloader slides across making the pump go into bypass – stopping further pressure build up into pump, hose & gun. Water is diverted to intake & circulates around in the pump manifold.

Without the unloader valve, the pump would over pressurize – damaging the pump, hose & gun and possibly stalling the engine. The unloader valve acts also as a Safety Device.

While you have let go of the trigger & the pump is in bypass – heat is building up – quickly. Some pumps are fitted with a Thermal Relief Valve. (Dump Valve). The Dump Valve will open between 60-63oC, allowing hot, heated water to escape & allowing fresh water in.

If heated water has or is coming out of the Dump Valve - you are letting the pump get too hot & allowing damaged to take place.

This is designed to protect the Check Valves & Seals. Allowing your Pressure Washer to run on with the trigger closed for more than 2 Minutes – is ‘asking for trouble’. Either:

· Turn down engine revs & or pressure adjustment handle on pump OR

· Turn Unit Off.

· Pull gun trigger a few times until you can get to your machine – this will allow how water out & fresh water in.

Sudden Loss of Pressure but Pump NOT Leaking

· Inspect the Check Valves & O Ring Seals

(3 Inlet & 3 Outlet – located behind the 3 brass plugs on front & on top of manifold.)

If they look deformed & the plastic housing looks melted and/or are tight to get out , they will not properly support the stainless steel valves & will not seal properly.

It only takes for 1 of these valves to not be working properly to lose pressure quickly.

· Check that the O Ring Seals at the base of the Check Valves are in good condition, not broken or melted.

If Check Valves appear to be damaged, replace them.

With sudden loss of pressure – Check Valves are normally the first thing to suffer damage.


· Letting Pressure Washer run on for too long without pulling gun trigger during operation - allowing water & pump to get too hot.

Gradual Loss Of Pressure with Pump NOT Leaking

· Inspect Piston Plunger Seal Kit

If the pump manifold slides off the piston plungers very easily, they are possibly worn out & will need replacing.

Inspect for signs of wear to parts of the seals.

Check Oil Seals located at back of piston, positioned into crank housing for signs of leaking.

Check Unloader Valve O Ring Seal – installed on nose cone of valve.

If pieces of the Seals / O Rings are broken or worn - replace full piston seal kit.

· Inspect Ball Bearing Valve

Check for signs of corrosion.

Located in under base of the Pressure Adjustment Bolt/Handle.

Although made of Stainless Steel, it can show signs of pitting & look rusty.

The Ball Bearing seals into a stainless steel seat and if it is not in good condition, full working pressure is not achievable.

If Ball Bearing looks damaged – replace.

(This is NOT a common issue & depends on water quality.)


Heat / Over Pressurized / Pump Running Without Water Flowing Thru / Impurities in Water / Wear & Tear fects of Constant Heat

Constant heat can soften & damage the Oil Seals positioned behind the piston plugers inset into the Pump Housing.

This allows pressurized water to pass thru into the Crank Shaft Housing & mix with the oil.

Oil colour goes ‘milky’. This will heat up the Crank Shaft & shatter Piston Conrods through poor lubrication.

Pumps with Viewing Windows can melt & let oil out of the pump.

Generally – this is TERMINAL. Time for a new pump!

Servicing Pressure Washer Pumps

1. Replace Oil regularly (30 hour intervals or 6/12 Monthly depending on usage.) Check Manufacturers Specifications.

2. If oil removed is milky in colour – oil seals are damaged – replace full Piston Seal Kit.

Axial Pumps – With Wobble Plate

If there is no Pressure Adjustment Handle then the pressure is Factory Set & locked off with locking nut. DO NOT ADJUST THIS BOLT or you will over pressurize your pump & blow the seals. It has been Factory Set to give the best, reliable operating pressure.

Crank Shaft Pumps With Adjustable Pressure Handle

For best long term operating pressure, DO NOT screw down Pressure Adjustment Handle to Maximum! This will put additional pressure on seals & this can overheat pump.

Screw Handle Clockwise down to about 75% of the full distance. This should be all you need for heavy cleaning.

If you cannot quickly touch your pump – you are letting it get too hot!

For increased pressure – try using the correct sized Turbo Head or narrower Spray Nozzle.

New Or Old Pressure Washer Engine Won't Start


  • Ignition Switch is turned to ON
  • Slide Fuel Lever across to ON
  • Slide Chock Lever across to CHOKE
  • Ensure there is fuel is in tank
  • Ensure Sump Oil is full (Filler Cap either side of engine)

Note: Due to Low Oil Shutdown – Oil Sensor Switch in Sump requires oil to be at HIGH level

(FULL means starting to come out of dipstick hole when engine is on level surface.)

If not enough engine oil in sump – ENGINE WILL NOT START.

· For some engines in warmer weather – leave Choke OFF prior to starting.



If you have checked above & your engine still won’t start :

1. Check For Spark – If NO SPARK:

· Check Spark Plug integrity

· Check Ignition Switch is earthing properly against engine housing

(A layer of paint can prevent contact of ignition switch earth pin)

· Disconnect or Bypass Low Oil Shutdown Switch

2. If you have SPARK

· Check Fuel Tank for debris – If found – Drain Fuel Tank

· Check Fuel Bowl – Look for signs of oil or debris -

If Pressure Washer has been on its side or turned over, oil will feed thru to Fuel Bowl & mix with fuel, stopping engine from starting.

· Check Valve timing

If rocker has come loose, then valve won’t allow fuel to enter cylinder head and timing will be out.

Any backfiring is a sign valve timing is out & needs to be reset.

This work should be done by a qualified person, your local mower shop or similar can reset valve timing. (Approx Cost $30-40).

Valve timing can work loose on any brand of 4-Stroke Engine, this is not common – but does happen.

Servicing Pressure Washer Engines

· Change Engine Oil after every 50 Hours

(Normally Castrol Modern Engine Oil 15W 40)

· Check Air Filter is clean

· Check Spark Plug is clean

· Check Fuel Tank for any debris in fuel

· Check Fuel Bowl is clean from debris

Over 35 Years