Power Washer with No Pressure


Old 06-04-10, 10:48 AM
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Join Date: Dec 2008
Location: Washington PA
Posts: 178
Power Washer with No Pressure

I looked at my buddies power washer today:

Gernerac GP TH Series 57 TH3020G

It has a nice little briggs 6hp engine that starts right up. We shut it off. hooked up the garden hose and pressure hose and wand, held the trigger open, started her up...water comes out the wand but with no more pressure than the hose would generate by itself.

My guess is the pump is shot, or the pump impellar is gone. I have never pulled one apart.

Any help would be appreciated.

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Old 06-06-10, 08:38 AM
Join Date: May 2010
Location: U.S.A.
Posts: 16
Preasure washer pumps are piston not impeller pumps... most come with an "O" ring rebuild kit that gets tossed along with the owners manual by "Tough" guys that don't need that stuff

And another frequent problem is storing in an un heated shed through the winter without winterizing (simply feeding some winter windshield solution Aka Blue juice through the detergent pickup tube)

Another problem is when the o rings wear out water and detergent can leech into the oil and after sitting through the winter the oil turns to a whitish gooky taffy....replace all the o rings (model specific pump rebuild kit) and change the oil twice over the course of two weeks

Edit .. When changing oil in any compressor or preasure washer pump you must use nondetergent (non foaming ) oil ...The 18 yr old kid at the autoparts store might not know what the hell you're talking about .. but The Guy at your local lawnmower, outdoor power equipment shop will grab a quart for you without batting an eyelash ...also keep in mind that homeowner designed preasure washers (Generac , MTD, Home Depot, Costco bought units will usually only take 20oz of oil ...Know how much your pump needs and don't overfill

Last edited by TheBlackLab; 06-06-10 at 08:45 AM. Reason: additional info
Old 06-06-10, 10:46 PM
cheese's Avatar
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Join Date: Jul 2001
Location: USA
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I'd say your unloader valve is most likely stuck. This is the case in probably 9 out of 10 pressure washers I look at with this problem.

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