Outdoor Power Equipment and Small Engines - Pressure washer over pressure and burst hose.

I have a Sears 3000 psi washer with a 9 hp Briggs engine. The pump model number is XMV 3G30.
The problem is that it went crazy and was stalling the engine until the pressure hose burst.The hose was in excellent condition until this happened.
I am ignorant of how these things work,however, but I read somewhere about an unloader valve that may be the problem. What do these things look like, where can I find it, and how can I check it?
I am mechanically proficient and have more that adequate tools to disassemble this thing. I just don't want to mess something up that will cost me lots of money.
Any help will be appreciated. Thanks in advance. Mike
P.S. This is my first post.

Wow, there should have been a pressure relief valve that kept this from happening, but yes, the unloader valve apparently stuck. The unloader is different and looks different on different pumps. Go to sears website and look up your model number on partsdirect. You can view a diagram and parts list of your machine there.

I went to the Sears website and found the parts list and(yikes!)price. They want $101.00 for that gold plated item. Mine bolts to the pump head and has the pressure regulator built in with it.
It doesn't appear like there is much to them. I tried to get the plunger out of it but it was not going to come out without applying some force. I don't know if it will come apart or not. Can these things be rebuilt by the average Joe, or must they be replaced? The reason I ask is Sears lists the part as an unloader "kit".
Thanks,
Mike

Yes they can be rebuilt if they are in good enough shape to rebuild. If you can't get the valve out, or scratch/damage it or the valve body while trying, you'll need another.

I found the manual for this thing!!!! Not much help beyond drawing of the pump.
Having read the manual, it has brought up a question. I want to change the pump oil while I am messing with this thing and the book says use non detergent 30 weight. On the pump sticker it says use 20w40. Which oil should I use or do you have a recommendation which you feel is better?

Thanks,
Mike

I'd probably go with the 30weight myself...especially since you'll probably never find a 20-40 weight oil.