We have a Karcher G2500VH pressure washer. If you start the engine with the trigger pulled on the spray wand it will run at full pressure until you release the trigger. after that, when you pull the trigger it will not have any more pressure than the water hose feeding it. Does it have an internal unloader valve? What is the part number?

Hi Cliff:
My experience is that the pump pressures prevent the engine from starting, so we hold the trigger while starting.
My brother has cut a wedge of wood that he uses to jam the trigger open to bypass the problem. It can get a bit wild if the wand is not secured when the unit is started..

Check for a clog.

take the hose off the washer pump and start it. if you have good water pressure then you may have something on the hose or the wand. I had a lizard in mine that caused that problem before.

If you have a Karcher then you should always post your machines barcode.

full article on nozzles :
http://repairshed.blogspot.com/2013/09/pressure-washer-lance-nozzles-what-you.html

The spill valve operates at approx 20% higher than specified pressure washer operating pressure. If you have any lance issues then the pressure could be running higher than specified (machine running at same pressure as spill valve operation pressure)

your machine produces a fixed flowrate of water (maybe 8 litres per minute) and your nozzle is a fixed size. the diameter of the nozzle determines the back pressure. A piece of debris could further close your nozzle orifice and increase the back pressure. Using a new lance that has the wrong nozzle fitted can also cause this issue.

The karcher barcode is on a silver sticker and is usually 15 digits long. Example 156987400000123 is actually model 1.569-874.0 and serial number 00123....

spill valve is stuck and needs to be cleaned and greased common problem....also check all connections for blockage in line

When you run the unit and shut if off, release the pressure from the spray wand before trying to restart the engine. This built up pressure will cause it to be very hard to start as you have found out. If it does not start on the second pull release the pressure again. Another option is do do what I did on mine. I simply put a pull tie on the handle so I can pull the trigger back and use the pull tie to hold the trigger open. Make sure if you do this, that you remove the high pressure orifice from the end of the wand before attempting to start the engine. Otherwise the pressure will come on abruptly and could injure you or do property damage.

hi,
there is a small ball bearing inside the nozzle on the end of the lance , this can get jammed or missaligned and the nozzle orifice can get blocked , clean this or replace the whole lance with another 200 Bar lance .

hope this helps

Hello awcockerill:
This sounds like the bypass (unloader) valve is sticking. Here is a diagram of your machine's pump. On page 2.4 see part #1. The top of this assembly is a black plastic cover. Remove all of assembly # 1 carefully. Under that is part #8. This is the bypass valve. You need to pull this out, check that the o-rings are not bent, worn or damaged, then lube it good with a VERY VERY good waterproof grease. Re-assemble it and all should be well. The part numbers are on the diagram but where to get them depends on were you live. Karcher web site may give you a number to call. Good luck.

I have a similar problem and diagnosed it to be a problem with the gun. I spoke to a technician that services this pressure washer and he walked me through all the diagnostic steps. The pump is working because there is pressure being built up and the gun sort of works because you can get water out before the washer is started. The technician said that the mechanism inside the gun is either clogged or broken. I am going to Home Depot or Lowes to purchase a new gun and will try it tonight. Guns are only about $30-40. He said generic is fine as long as the thread matches and PSI is in range. Good luck!

To determine if your problem is due to an easily replaceable part, follow these steps:

1. Connect the water supply hose, the pressure hose, and the wand WITHOUT any nozzle tip.

2. Turn on the water supply, and press the trigger until water is smoothly running out of the nozzle
after any air is all purged out. Release the nozzle trigger.

3. Start the engine, and let it warm up for about 30 seconds.

4. With the engine running smoothly, press the nozzle trigger. The water should flow out of the nozzle (without the tip installed) at a faster rate, while the engine noticeably loads down as it used to do before your "no pressure" problem. If it does not load down, turn it OFF, and disconnect everything, and contact a Karcher repair facility.

5. If the engine does load down, release the trigger, and install one of the nozzle tips (not the black one).

6. Press the trigger, and the engine should load down, and you should have normal pressure from the wand. After you release the trigger and press it again, you will probably again have no pressure, and the engine will not load down. Removing the nozzle tip, pressing & releasing the trigger, and re-installing the tip should give you normal pressure again, but releasing the trigger will cause no pressure until you again remove the tip, press the trigger, and re-install the tip.

This is caused by a bad UNLOADER VALVE, which is located under a black cap with a metal button on it located on the top front of the pump. I don't know if you can purchase the replaceable parts from a Karcher repair shop, but when a neighbor & I took his washer to a repair place, it looked pretty simple to do this repair, and he was charged about $60 to replace a $5 (maybe) part, and it took about 5 minutes.

To determine if your problem is due to an easily replaceable part, follow these steps:

1. Connect the water supply hose, the pressure hose, and the wand WITHOUT any nozzle tip.

2. Turn on the water supply, and press the trigger until water is smoothly running out of the nozzle
after any air is all purged out. Release the nozzle trigger.

3. Start the engine, and let it warm up for about 30 seconds.

4. With the engine running smoothly, press the nozzle trigger. The water should flow out of the nozzle (without the tip installed) at a faster rate, while the engine noticeably loads down as it used to do before your "no pressure" problem. If it does not load down, turn it OFF, and disconnect everything, and contact a Karcher repair facility.

5. If the engine does load down, release the trigger, and install one of the nozzle tips (not the black one).

6. Press the trigger, and the engine should load down, and you should have normal pressure from the wand. After you release the trigger and press it again, you will probably again have no pressure, and the engine will not load down. Removing the nozzle tip, pressing & releasing the trigger, and re-installing the tip should give you normal pressure again, but releasing the trigger will cause no pressure until you again remove the tip, press the trigger, and re-install the tip.

This is caused by a bad UNLOADER VALVE, which is located under a black cap with a metal button on it located on the top front of the pump. I don't know if you can purchase the replaceable parts from a Karcher repair shop, but when a neighbor & I took his washer to a repair place, it looked pretty simple to do this repair, and he was charged about $60 to replace about a $5 (maybe) part, and it took about 5 minutes.