Looking for manual for honda pressure washer,its a GX 340 11.0 HP that I can view online without buying so I can find the part and part number

If you are looking for parts for this machine, you'll need to know the model number; if it is for the engine, the name (Honda, Briggs & Stratton, etc.) and the model number to it. If you still have the owner's manual, there is usually in the appendix, a schematic along with a parts list page.
You can easily go online and enter the "Home lite" brand name of the pressure washer, the model number plus the words owner's manual.
Same thing for the engine.
There are many online manual sources.

MiTM will have that. See mitm.com Honda makes the motor but not the pressure washer. Honda does have manuals if you need one for that GCV160 motor.

go to honda and enter info

It has quite allot of hours on it so it has been used extensively. 283 hours on a pressure washer pump is about 27% of it's life expectancy. The good news is that it has a Honda engine. If it runs perfectly, looks like it has been taken care of, and has plenty of pressure, I would pay no more than around $400 for it tops. You are the buyer and the seller is wanting to sell. You have the upper hand in this deal. Offer $300 and then bargain.

The numbers you have listed are for the engine, Honda doesn't actually make pressure washers but makes the engines. If you are looking for the manual on the pressure washer itself you are going to have to find some other numbers that should be listed on the frame of the machine.

Were I to pick from one of those three, I would pick the Landa. The most reliable pumps are Hotsy and since Karcher bought Landa and Hotsy, those three brands now have Hotsy pumps, though it doesn't say it on the machines.

http://www.honda-engines.com/Engines_owners_manuals/ownersmanuals/gx390.htm

Hi, this is manual for engine only. maybe of some use.

There are no manuals for Dewalt at either of those sites.

I managed to find a free Download of the technical manual on the internet so this covers all questions about the engine

I think both problems could be wiring in the key switch box. Sometimes the connectors shake loose.