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Craftsman Pressure Washer/Briggs Engine Surging at Idle


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03-17-07, 01:56 PM   #1  
Craftsman Pressure Washer/Briggs Engine Surging at Idle

I have a Craftsman 2400 PSI pressure washer with a 6.0 Horsepower Briggs Intek engine. It had not been used for a few years and the gas had gone bad in the carb bowl (the tank had been emptied). I cleaned the carb to like new condition, replaced the needle, seat, and float. That fixed my flooding problem which spilled gas out through air cleaner when unit was shut off. However, I have another problem that it did not fix.

Problem 1:
When the engine is running under load (trigger on wand pulled) it runs GREAT! When you release the trigger it sounds as though the governor is getting a workout. The engine surges up and down continuously until the trigger is squeezed again. Can someone tell me what I need to do to get this thing to idle smoothly?

Problem 2: (This may or may not have to do with problem 1)
When at idle, the pump seems to pulse about every 2 seconds. When it does this, the feed (garden) hose along with the high pressure hose jump. Does anyone know what is causing this?

 
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03-17-07, 10:20 PM   #2  
I believe both problems are related to a sticking unloader valve. These are different in appearance and location on different machines, so you may want to go to sears website and look up the parts diagram for your unit to identify the unloader.


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03-18-07, 06:44 AM   #3  
Surging Help

Posted By: cheese I believe both problems are related to a sticking unloader valve. These are different in appearance and location on different machines, so you may want to go to sears website and look up the parts diagram for your unit to identify the unloader.
I looked on the parts diagram and found the valve. I removed it and found a few small pieces of grass around the base of it. Could this have been causing it. Also the piston inside the valve seemed to move fairly freely by hand. How much movement does this thing require? Can I lube the piston to make it move more freely?

Thanks for the help!

 
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03-19-07, 03:03 AM   #4  
The grass could be the problem. I like to disassemble the piston/valve assembly and clean it up, replace o-rings if needed, and then I coat it with vaseline and reassemble.


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03-19-07, 07:41 AM   #5  
I cleaned the unloader valve but did not lube it with anything (I had not seen the post about vaseline yet). I put it back on the PW and used it yesterday for about 2 hours to clean my siding and gutters. Once again, it started easily and ran great under load. But, the second you let off the trigger, the pump surged. This time, I studied it and the engine (governor) surge was directly affected by the pump surge. Because of this, I am sure you are right about the valve! Do you think it is not moving freely enough? I got any gunk out of it that I could see. Do you think if I put some lube on, it would smooth out? What causes the surge? Is it the unloader valve not opening at all or is it opening and closing too fast?

Sorry for all of the questions and I greatly appreciate the help!!!!

 
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03-19-07, 03:19 PM   #6  
Azis
You may be describing normal operation. If as soon as you pull the trigger you get high water pressure, and as soon as you let go of the trigger, it stops, then the unloader valve is doing its job. If while the engine is under NO Load, it surges a bit, realize the engine throttle is at full and with no load trys to over rev. The governor restricts it then the cycle starts over.
The owners manual should explain about NOT letting the unit idle for over a few minutes.

 
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03-19-07, 08:36 PM   #7  
It does seem like I recall some units that do this, like Azis described. I think it's becasue of a leaking spraygun though. The pressure in the outlet line bleeds off as it leaks until the unloader kicks the pump pressure back on, but then it only takes a fraction of a second to build up pressure in the outlet line again, so it quickly unloads once again, and continues this cycle.


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03-20-07, 07:07 AM   #8  
Azis
I used the term "Normal Operation" only due to the fact that nearly all I have looked at seem to do this. I have thought about troubleshooting it further but the units all check out and operate properly. So I kinda adopted the "If it aint broke" theory

 
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03-20-07, 03:02 PM   #9  
Now that you mention it....I did see some water leaking from the fitting where the high pressure hose attaches to the pump. It never occured to me that this little leak could cause this thing fluctuate so much. I will check more into that and replace the o-ring on the hose if necessary and see if that helps the problem. Thanks for the help. This is a great forum!!!!

 
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03-21-07, 09:16 AM   #10  
A little water leak should not cause the problem(s) you describe. I don't think I've ever seen one that didn't leak somewhere.

While working on the engine, you should never run it without water going to the pump as the pump can easily burn out if not cooled by the water.

You should also have a pressure adjustment on the pump. Look for a black knob underneath. Start off with the valve wide open and slowly turn it until you reach the desired pressure. The Craftsman manual for these washers is pretty good. It might be wise to read it in detail before going any further.

You don't say how old the unit is but older Craftsman pressure washers used an Italian made pump for which parts are no longer available. There's more than one machine arounnd here with a perfectly running engine and no pump. Pretty useless once the pump goes.

 
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03-21-07, 03:05 PM   #11  
I have not run it without water so I am pretty sure the pump is ok internally. However, I have heard some folks talking about checking/changing their pump oil. I have a clear plastic hex bolt on the side of the pump with a red dot painted in the middle. Is this a sight glass for checking oil? The manual specifically states NOT to mess with the oil. It says "Your pressure washer pump is a sealed pump, you should never have to change the oil." If that is the case, why the sight glass? Also, I cannot see any oil in the pump through the glass. Is this a concern?

Finally, I have found the pressure adjustment knob on the side of the unit and have turned it all the way in both directions and everywhere in between with no success in solving the surging.

By the way, I am not exactly sure of the age but the date on the manual says 12/1/98 so that is probably within a year or so!

I think my next move will be to change the o-ring on the end of the high pressure hose to see if fixing the leak has any affect on it!

 
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03-22-07, 02:00 PM   #12  
I was just looking at a Craftsman unit today doing about the same thing. Problem was a tiny bit of debris partially plugging the tip of the nozzle. The spray nozzle has a hex socket head; required a 5/64 allen wrench to screw it out. Wasn't sure how it got into the line but when I checked the inlet filter screen, it was badly clogged and when somebody tried to clean it out with a screwdriver, he/she punched a hole in the screen.

Ran it for a couple of minutes without the nozzle just to make sure the lines were flushed out and clear then put the nozzle back in. Runs great now.

 
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03-23-07, 01:06 AM   #13  
How does a bit of debris affect the washer at idle when it's not spraying? I think it's either the leak on the pressure line or back to the unloader if correcting the leak doesn't solve the problem.


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03-23-07, 07:06 AM   #14  
Azis
I am still not sure that we are all talking about the same symptom(I may be odd man out). Surging in my understanding, would be a lean condition which causes the engine RPM to increase then decrease and nearly or even die as if it ran out of fuel, (which it nearly does or does) then suddenly come to life and rev up again.
What I am refering to here is as if the throttle was being changed from idle to full back and forth. I agree a leak or problematic unloader valve could cause this. If no leaks can be found to repair, and the unloader valve has been addressed, I think checking the idle speed and possibly govenor settings, then replace the unloader since its operation can not be verified.
If the idle speed is set too low, it could cause this.

 
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06-26-09, 02:13 PM   #15  
I have the same symptoms with my 2004 Craftsman 2700 PSI pressure washer with a Briggs Intek 7.0 HP engine. I think Azis is on the right track with a lean condition. I found that if I set the choke lever one detent position toward Choke from the Run position, the engine will run smoothly whether or not the engine is under load. These symptoms started the second year I owned it. They are present about 90% of the time. It doesn't matter whether the engine is hot or cold. I suspect that a fuel passage or jet in the carb has a thin layer of some deposit on it from that first winter storage causing a lean condition. I tried a small amount of Seafoam Fuel System Cleaner in a full tank of fuel, but it did not help. I have left well enough alone and lived with it rather than tearing the carb apart and cleaning it since it runs perfectly in all other respects.

 
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