Pulsating Kracher K 5.55?

HI,
I have a Kracher K5.55 pressure washer which blew off the high pressure hose connecting sleeve. I have since replaced the sleeve, but now re-assembled, the machine pulsates every second or so when at rest ( trigger not squeezed on gun) plus the pressure is low when a lance is connected and trigger operated. I have bled the unit, extended the inlet hose to 20m, looked for signs of leaks, and given it a good glare...Help please!!