Pressure washer help

[antnee]

I was using a pressure washer today on my car, had been on for about an 45mins-1hour, I turned the car around (was parked on the road) went to do the other side and the pressre was way down
Thought it might be some temp cut off but went to try it just now and its the same. It still is making the usual noise but isn't pumping the water any faster than normal tap pressure.

Any ideas what I could try?

(its a JCB 1800)