Pressure washer pulses rhythmically

[rslaback]

I know a bit more about pressure washers than the average chap but this one is a new one on me.

I picked up this Karcher washer cheap. I was told that it wouldn't build pressure. The gun had obviously froze with water in it and cracked the tube so I changed that out with a spare I have on hand. It would pulse and bog down. Eventually it got hard to even pull the rope. I took the pump completely apart and checked for stuck valves, ripped seals and plugged passages. The bearing was seized a bit so that was dealt with. I'm back to the pulsing action.

The unloader valve seemed fine but I wonder if a seal is leaking water around it or if the housing cracked in that area. I pinched off the soap tube in case that was allowing air into the system. I suppose it could be a dirty emulsion tube in the carburetor preventing it from spooling all the way up but I would expect starting issues and for it to die instead of pulse under load.

Before anyone suggests too low of water pressure, this big dog runs fine on the same hose.

 

[5ubtle]

If it stops pulsing on partial choke, it is running lean.

 

[rslaback]

It's got an auto choke but it will give me a backfire pop every now and then at shut off so i don't think it's starving.

 

[scooby074]

Maybe it identifies as a drummer.

 

[5ubtle]

Hold the governor linkage (throttle plate) steady and see if it still surges. If so, I think that it's in the engine (probably carburetion), if not, I think it's in the pump.

 

[The Cobbler]

sounds like a carb/governor issue over a pump issue to me

 

[rslaback]

Well, I cleaned the carburetor as a long shot. Same behavior.

 

[5ubtle]

My pressure washer did the same until I changed the jet. Figure out how to activate 'partial choke' as a test.

 

[rslaback]

My pressure washer did the same until I changed the jet. Figure out how to activate 'partial choke' as a test.

This uses a Tecumseh Centura engine. They don't have a choke. They rely on the operator to pulse the primer bulb enough times to semi flood it and use that as a choke.

 

[theoldwizard1]

Well, I cleaned the carburetor as a long shot. Same behavior.

It is still the carb !

Did you remove the idle/pilot jet and make sure it is clear ?

 

[rslaback]

It is still the carb !

Did you remove the idle/pilot jet and make sure it is clear ?

Yes. The Centura carbs use a plastic emulsion tube. That was removed from the body, all parts went into a heated ultrasonic cleaner for the better part of a day before being removed, the passages chased with a 61 to 80 drill set and blown out before reassembly.

The jet is built into the carbs bottom nut. It got the same treatment including the angled passageways getting chased as well as the center hole.


It wasn't the first carburetor I've cleaned. Or likely even the hundredth at this point.

After it didn't make a difference on the pressure washer, I also installed the carburetor on a different 195cc Centura mounted to a walk behind string trimmer where it preformed perfectly.

 

[rust in the eye]

It's got an auto choke but it will give me a backfire pop every now and then at shut off so i don't think it's starving.

It's lean. Clean the carb out and check for vacuum leaks.

 

[5ubtle]

Partially cover the carb inlet with your hand (or credit card, or whatever).

 

[Renegade1LI]

Sure sounds like the unloader valve or maybe a crack in the pump & it's sucking air.

 

[Zewnten]

The unloader is failing.