Common Pressure Washer Repair Problems

By London Fog

October 10, 2020

Some pressure washer problems are quite common. But thankfully, most of them are very easily (or at least moderately easily) solved. And moreover, fixing them yourself if you can save you both time and money.

Here, we’re going to walk you through some of these problems, from identifying the problem through to solution. We will start with some of the most common problems of all.

Possible Problems

Pump Problems

There are two main causes of pump problems. 

One is overheating, which is caused by running on the pump on too high a heat of an excessive level of time. The solution is to ensure that you ensure that you don’t keep the pump running when it doesn’t need to be on.

Sure it’s easy to get distracted and forget that you’ve left it running, but if this has become a common occurrence, then you really need to address it.

The other main pump problem is pump cavitation. Pump cavitation is the rapid creation and subsequent collapse of air bubbles in the water. This is caused when there is not enough water supplied to the pump.

To correct this problem you must ensure that the supply to your machine pushes out higher gallons per minute than the rating on the pump.

Low Pressure

Quite often, low water pressure is caused by dirt in the pump. Dirt or debris in the system can cause a blockage which prevents the water from adequately moving through at the right pressure.

This blockage may appear anywhere in the system. So what you need to do is take the parts off and disconnect them from each other. If you can’t spot an obvious blockage anywhere, then use the process of elimination.

For example, you can try replacing the nozzle and seeing if that makes any difference. Then try replacing the extension, then the gun etc (well, if possible). Once you’ve zoned in on exactly where the blockage is, then all you have to do is clean it out, and all being well, it should work right as rain.

In the longer term, though, what you need is to ensure that all the water in the pump is clean.

Also the problem could lie with the nozzle. It could be the wrong size or it could be worn out. Check them regularly, and get them replaced when they’re too worn. You should also ensure that you have spares at hand for this very issue.

No Pressure at all

If there doesn’t seem to be any pressure at all, then this often comes down to a faulty pump inlet valve or unloader valve.

What you need to do in this instance is to see if either piece is clogged, and get them cleaned. If the problem still persists, then this is a clear sign that the valves need replacing.

Or it could be down to damaged pump inlet valves. In which case, what you need to do is disassemble the pump and clean the various components of the inlet manifold. If this doesn’t work then you may need to replace the parts of the inlet manifold.

Running Rough

When the water is running rough, it sounds like the machine is choking. Nine times out of 10 this is usually because the inlet water is too hot.

Try using only cold water, and see if the situation improves.

Sometimes this can happen even when you’ve only been using cold water. This is because, if the pressure washer is left outdoors, water that has been trapped in a hose can be heated up by the sunshine.

Another factor that can cause the pressure washer to run rough is if you haven’t got enough air going through the inlet plumbing. To create the pressure in the system, you need to have the right balance of air and water.

So, if you’ve deduced that rough running isn’t being caused by hot water, then check the air filter of the pressure washer to see if it needs to be replaced.


If you are using a low quality hose with your pressure washer, then kinks in the hose can cause leaks. And sometimes they’re so small, they can be hard to spot. 

And of course you could get leaks at the seals. When the pressure washer is completely set up there are a number of different seals throughout the system. And it only takes one failed seal to cause a leak.

It’s not always too clear what causes a seal to spontaneously break and leak. The only real way around it is to check all the seals at least twice a year to ensure that they’re not getting too worn. And when they are worn, be sure to get them replaced.

If the water is leaking from the spray wand connections, then this will be because there’s a broken O-ring inside the connection which needs to be replaced.

Pulsating (high followed by low pressure)

If the water seems to be pulsating through the system, then the chances are that this is down to either a dirty inlet, or discharge valve. 

You can work to prevent this by cleaning them out really well every 5 or 6 uses or so.

This is particularly important if you regularly pressure washing decking because high pressure water can cause the wood (even hardwood) to splinter. 

If your inlet and discharge valves are clean however, then the pulsating can be caused by a stuck plunger. And if at the same time you’re also getting low pressure, then this is a strong sign that the problem is a stuck plunger.

Another potential cause of pulsating pressure is if the pump is faulty and is sucking in too much air.  In which case, what you need to do is to turn the machine off, and squeeze the trigger of the gun to get rid of the excess air.

Spiking Pressure

If the pressure seems to spiking (rather than pulsating) then this is probably because the unloader valve isn’t properly calibrated. 

What you need to do is to adjust the unloader to the proper pressure as per your user manual.

Pressure drops after a few seconds

If the pressure drops after a few seconds, the first thing you should do is check to see if the nozzle is blocked. Clean it out with a needle like object.

If that doesn’t fix work and you still have the same problem, then this is most likely an issue with the unloader valve. In which case you need to remove the unloader and clean or repair it (or replace if necessary).

Sudden Shutdown

If the pressure washer suddenly shuts down, this is usually down to one of two things. Either you have run out of oil or you have run out of fuel.

The way around this potential issue is to always check the oil and fuels levels before each use of the machine. Make it a habit, a standard part of the pressure washing ritual.

If it’s clearly not an oil or fuel problem, then it could be a dirty air filter, in which case you need to clean it.

Pressure Washer Not Starting Up

Sometimes a pressure washer won’t even so much as start up. Even after you’ve ensured it’s got plenty of oil and fuel.

If this is the case, what you need to check next is the primer pump. Pump the fuel primer 6 or 7 times and try to restart the machine. Then do 2 to 3 pumps for the next pulls.

If it still doesn’t work after this, leave it rest for a few minutes and then run the choke on full.

If none of this makes any difference then it could be a problem with the spark plug, in which case you’ll need to get it replaced. 

Pressure washer isn’t cleaning the surface

If the surface your cleaning doesn’t seem to be cleaning well, this is often because you’re using the wrong kind of nozzle on the end.

If so, all you have to do is change the nozzle to a higher pressure spray nozzle. It’s handy to keep a selection of nozzles at hand in case a nozzle gets damaged.

Final Word

Just as your outdoor space needs regular maintenance, so does your pressure washer. A little TLC now and then can go a long way.

More often than not it’s just a case of making sure everything is clean. Doing regular checks on your equipment really does pay off in the long run. Prevention is better than cure as they say.

Remember pressure washers and their parts are more often than not universal, so getting the right kind of replacement parts is easy, especially with the larger online retailers such as Amazon.

Of course there will be times when try as you might you just can’t repair the beast, and instead you’ll have no choice but to buy new.

When that time comes, be sure to check back here to get some really good advice and some decent pressure washer reviews.