98 Range Rover EAS pump problem

there is a slow leak in the lines to the system.
SO after sitting a while, my rover will be sitting all the way down. after I started it up I was able to hear the compressor come on, and after several minutes the system will fill up and the rover would go up. And I was able to drive it without any problems.
the other day I wanted to go for a ride, I started it up and waited.... only this time it never did go up. I listened for the pump to come on and could hear it come on, but after just a few seconds it would go back off. I was able to jump leads to the compressor and it works.
I was able to check the relay and the fuses under the hood; I found the timer relay under the drivers seat and they all checked out fine.
Is there another relay or sensor somewhere else that I have missed?
Is there someone who can help with an answer to this problem?