I think I have all the hoses connected correctly and there is flow through the wand before I start the engine. But when the engine starts and I depress the trigger there is an brief spurt and then nothing. Not even the flow that the garden hose provided earlier. The trigger moves freely but nothing happens. When I shut the engine off the trigger again controls garden hose flow. There are no leaks or spray at another part of the hose or wand with or without the engine running. It is as if the engine pressure closes something off.

Disconnect the output hose, and start unit, see if there is water always going though.

Then we can go from there.

The water flowed freely with the output hose disconnected and the unit running. It also flowed freely with the hose connected, unit running and the wand disconnected. So it would appear the problem is with the wand. What now?