I have a 5hp electric pressure washer that uses a CAT 3DX pump. The pressure has been falling off and now is at a point that it is virtually unusable. The input filter is clean, I took the unloader apart and things look OK in there. I am now left with the pump itself I think. I pulled it apart (the 8 allens and the 3 caps). The pistons look OK, looking in the holes, I don't see anything obvious with the check valves, no broken springs, no contamination. I can see all the way through all the passages and they are open. I think I am down to ordering a rebuild kit but by the time I get a seal kit ($90) and a check valve kit ($164) I am 85% into the price of a hole new pump assembly with everything attached.
This is a $700 pressure washer, the pump is $300 and the kits are $254 plus shipping.
At this point I am about to start pumping WD40 or some other solvent through it to see if that doesn't free something up. I don't see I have much to lose since tossing the pump is the next step.
I would really enjoy hearing something better since I have another CAT
4 piston pump on the shelf that is bad the same way and a little electric pressure washer that doesn't work that well either.