Hi top, welcome back.
Troy Built equipment is not sold here in Australia as far as I know, but the systems are likely to be generally similar to the pressure washers we see here. Where there are differences, we'll have to rely on asking questions and working out what is going on, together.
Let me tell you how the pressure washers I'm used to, work. After you apply water pressure, you start the engine. You should never start the engine without water pressure applied, because it would ruin the pump. I've never tried doing it, to see whether the engine stops automatically, because I don't want a ruined pump.
As long as there is pressure at the pump inlet, the engine runs at governed speed. There is a screw adjustment to set the governed speed, but it is usually a good idea to follow the manufacturer's recommendations. If the spray wand is shut off (that is, the trigger is not pulled) the pump automatically bypasses because if it didn't, the water would boil in the pump and there would be cavitation damage. Consequently the engine is running at governed speed, but under hardly any load, so it runs fairly quietly. When you pull the trigger on the spray wand, water flows through the pump and the engine has work to do, raising the water from the water supply pressure of about 60 psi, to the pump output pressure, which is 2,400 psi usually if it is a pump with a 5-6 hp engine. Because the engine is suddenly working hard, whenever you pull the trigger the engine's governor opens the throttle and the exhaust noise increases greatly, but the actual speed stays the same. When you release the trigger, it quietens down again.
Now, does your pressure washer do the things I've described? If it does, it sounds as if it is working properly.
