Your lawnmower motor is knackered or, if it uses a capacitor phase shift for the motor, the capacitor is knackered (Cheap enough off EBay but get the right value and physical shape) or something is stopping it from running (seized)
Not a lawnmower? Why post in the lawnmower forum?
If it's pressure washer, motor is knackered or, if it uses a capacitor phase shift for the motor, the capacitor is knackered (Cheap enough off EBay but get the right value and physical shape) or something is stopping it from running (pressure relief/bypass valve jammed shut, motor/gearbox/pump seized)
XXX, April 2016