Thanks for the reply Ian .i can count out points 1,2 ,3 and 5 . They have all been double checked . I also spent an hour yesterday recalibrating on different letters . I have left it on letter a . It's not quite right as when I open the pole tap it takes about 3 seconds to kick in,and when I close the tap it still runs for about 3 seconds . But when I recal it higher or lower it goes from one extreme to the other .so basically it will only work on letter a . And then on number 4 . If that makes sense 
thanks again for the reply . Cheers barry
A Varistream controller is factory set on C which they say is right when the controller is linked to a Shurflo pump. The standard Shurflo pump used for window cleaning is 100 psi.
The one Shurflo pump on my van is nearly 9 years old and in daily use. We run on C in the summer and D in the winter.
That setting allows us to work at a flow of 5. I use 5 if I'm on my own and have plenty of water - I love the faster flow for rinsing but I waste water during the scrubbing phase at this flow rate. My usual setting is 4 and 3 if we are short of water. (Using 3 really gets on my wick when rinsing though.)
There is sometimes a maximum delay of 4 secs on both my Varistreams. This will not be on start up but will be when the system has dead ended. When dead ended (when the system is pressurised with your water flow turned off), the controller sends a 'signal' every 4 seconds to test to see if there is a pressure drop in the line. If you turn on your tap just fractionally before the 'signal' is sent, then it will appear to you as though the pump has started immediately you have open your tap. If you opened your tap fractionally after the 'signal' was sent by the controller then you will have to wait for the next 'signal' before the pump will start again.
If you stand next to the pump with the pole tap off, just listen to the pump. You can hear when the controller briefly tries to restart the pump. It waits a while (4 secs with my controller) and tries again. The delay will be the time between these attempted restarts.
The calibrating numbers and letters on the pressure setting of the Varistream aren't actually pressure settings at all. They are related to the current (amps) draw of the motor. So you are telling the controller to stop the pump when it reaches the current draw limit you have set.
The lower your setting the less current you will use. This will mean that your battery will need charging less often, and your system will be subjected to less wear and tear.
We experience issues with 1 lot of minibore hose we bought a few years ago which was fitted to my hose reel. After the tap was switched off the pump continued to run for sometime afterwards. What was happening was that under pressure the hose was swelling and was acting like a reservoir. It was also making the hose reel difficult to turn. Reducing the deadend setting solved that issue but the pump cycled on our usual flow. The other symptom of this happening was that the water sprayed out of the jets when the tap was opened and we never experienced a delay before the pump started.
Using my sons hose reel solved the problem and help us the identify the issue. Replacing the hose was a permanent fix.