FILENAMES: pump1.jpg pump2.jpg pump2a.jpg pump3b.jpg pump4.jpg pump5.jpg pump6.jpg pumpfin.jpg DESCRIPTION: These are pictures of a repair to a pressure washer pump. Posted by Carl Byrns . The following description was provided: ================================================================= The text describes a repair I did on a pressure washer pump. Here's a picture of the original pump: pump1.jpg This pump is very popular on lower-priced "home center" gasoline engine type power washers. It uses a swash plate to drive three axially located pistons. The pressure regulator is internal and is a part of the main casting. The pressure regulator is, in my opinion, a poor design and (for me) has been a constant source of trouble. The built-in pressure control doesn't do a very good job of dialing down output and the shuttle valve tends to jam in 'bypass' which leaves a trickle of water coming out of the wand. Every time I squeezed the wand lever, I never knew if the shuttle valve would shift back out of bypass, or if I would have to pry the stupid valve apart. Again. A new pump costs $361.00 (more than I paid for the entire machine, on sale) and replacing just the regulator parts won't cure the problem (corrosion in the bore) so I decided to try adapting an external regulator from a scrapped power washer. The results are amazing: the original regulator was very restrictive, with a tiny venturi for a soap siphon. With that gone, the pump now pushes water at a serious rate. Best of all, the output is fully adjustable and the regulator cycles smoothly between bypass and demand. Here's what I did: 1)I removed the venturi, the flow control, the set screw that holds the regulator in, the soap fitting and check valve, and the old regulator valves. 2)Using the original bore as a guide, I used a 7/16 inch bit to enlarge the bore. I drilled right through the closed end of the bore. See pump2a.jpg 3)Starting from the formerly closed end, I tapped the bore to 1/4 inch NPT (National Pipe Thread). See pump2.jpg 4)The next part was a little tricky: Working from the originally 'open' end, I tapped the bore with the 1/4 inch NPT tap. The bore is way down in there and I used a socket wrench to drive the tap. 5)After a thorough chip flushing, I installed a socket head pipe plug on the inside of the bore. This plug divides the bore into two parts- output side and input side. Once the rest of the work is done, the plug will be inaccessible, so I coated it with JB Weld before installing. See pump3b.jpg. 6)Next, I screwed a 1/4 inch NPT by 1/4 inch compression fitting into the 'outside' end of the bore. Using a 1/8 inch drill bit and working carefully, I drilled into the fitting through the set screw hole. I drilled all the way through the fitting. This is necessary because the fitting blocks off the port that returns bypass water to the input side. The port is not on center with respect to the regulator bore. 7)I then removed the fitting and drilled the 'port' side open to 1/4 inch. See pump4.jpg 8)I Teflon taped the fitting and reinstalled it. I locked it in position with the set screw. 9)The threads that originally held the venturi body onto the pump were corroded and appear to be metric. I installed a 3/4 by 3/4 inch flare fitting (male X female) after applying a liberal coating of JB Weld- there was good thread engagement, but I wanted to be sure the fitting would not work loose. I used a 3/4 by 1/2 inch reducer bushing to match the pump outlet to the external pressure regulator. See pump6.jpg. 10)At this point, I reinstalled the soap siphon fitting and the original flow control (which is turned all the way to wide open). The only function these now perform is to prevent leaking. 11)The pump was then reattached to the engine and the external regulator was attached to the pump output port. A 1/4 inch diameter copper tube joined the regulator bypass port to the compression fitting on the intake side of the pump. 12)I reworked the venturi body as follows: I shortened the portion that screwed into the pump by cutting it just past the annular groove. The body has a very restrictive taper bored through the center which I opened up to a constant 1/4 inch diameter by drilling and then reaming. I then silver soldered the body to a 3/4 inch by 1/2 inch reducer. This assembly was then screwed into the regulator. See pump5.jpg Notes: the bolts holding the pump together are apparently corroded solid. Rather than risk breaking them off, I did all the machine work with the pump assembled. I flushed the chips during and after every machining operation (with spray brake cleaner) and then ran water though the pump for several minutes after all the machine work was done. After all that, I had one small chip plug the wand nozzle. Complete disassembly is obviously the better way to go, but not absolutely necessary. Here's the end result: pumpfin.jpg. The picture of the finished project is somewhat inaccurate because the assembly won't fit into pressure washer frame. In practice, there is a 90 degree ell at the pump output port.