start it up and keep ur hand on the trigger on the gun it will come throw there will be air lock in it, it happens when there is no water and it runs ry
No! not when sucking, the nozzle orifce is far to small to let all the air out.
Take any atatchment off the end of you high pressure hose EG lance/gun or surface cleaner, so its just a hose. Drop your suction tube (bigger than the mains water one at least 20mm) into the water filled butt. Start engine and run on LOW revs untill all the air is purged out, then stop engine connect your lance etc then start on full revs, begin work
If that don't work youve got a sucking air fault or faulty valve/s