If it is one of the cheaper pressure washers then they have a designed lifespan of around 50 hours, the pump has plastic pistons rather than metal and these fail seizing the pump
Pressure relief valve may have stuck so trying to start under pressure (thanks Tel). if it doesn't start with the trigger open, to release that pressure and put no load on motor, then as all others say - it's knackered.
Reply to Pressure washer fuse blowing in the Electrical Appliances Forum area at ElectriciansForums.net
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