Water system not working

[TMRAVEN]

I have a Holdsworth conversion and the water system inside has never worked properly.
I have managed to empty the water tank (once I found the jubilee clip to disconnected the pipe at the back of the tank), and refill.
The pump is working...it draws from the tank and pushes water out the other side. However when the pipe to the tap is connected to the outlet it won't come out of the tap. It appears the tap has a micro switch in it but to be honest I am not sure if it is working and what it is supposed to do, I mean when the tap is open does it rely on electricity to open something to allow the water through?
I don't know if this information will make the problem easier to diagnose, but when the pump is switched on at the zig unit it makes a noise continuously, so I am wondering if it was fitted wrong somehow and whether the pump should only make a noise when the tap is switched on?
I am thinking the tap is where the problem is...but the wiring doesn't appear easy to get to, and I don't want to throw money at a new tap then find out I a) can't fit it and/or b)it still won't work.
Any ideas or advice will be greatly appreciated, thanks.

[a1winchester]

If it's the same as my Autosleeper, then you are right. The tap has to be turned on for the pump to work.
The pump has to be primed with water before it will flow properly. You can achieve this by applying suction to the tap outlet

[AdrianC]

It appears the tap has a micro switch in it but to be honest I am not sure if it is working and what it is supposed to do, I mean when the tap is open does it rely on electricity to open something to allow the water through?
I don't know if this information will make the problem easier to diagnose, but when the pump is switched on at the zig unit it makes a noise continuously, so I am wondering if it was fitted wrong somehow and whether the pump should only make a noise when the tap is switched on?
I am thinking the tap is where the problem is...but the wiring doesn't appear easy to get to, and I don't want to throw money at a new tap then find out I a) can't fit it and/or b)it still won't work.

Sounds like the tap switch is indeed your problem.

+12v will leave the zig, to the tap.
When the tap's opened, the microswitch should pass that +12v to the pump.
The pump should put that +12v to use in pumping water to the tap.
The +12v then meets earth through the pump's other connection.

If your pump's churning all the time the feed is switched on at the zig, then the tap switch has failed closed - or has been bypassed, having failed open, so using the zig as a replacement pump switch.

What happens if you open the tap AND switch the zig feed on...? Opening the tap does two jobs - it actually opens the tap, but it should also turn the pump on. If the pump's running, but the tap's closed, no water can get through. If the tap's open but the pump's not running, then no water's being pumped (and there's no gravity or other pressure to push it).

If you want to get more detailed with what's actually happening or not, and what bodgery's previously been done to work around broken things, then it's going to be multimeter time.

[TMRAVEN]

Thank you both for your input. I will be having another look at it at the weekend, so will take your advice on board and see what I can work out.
Turning the tap on doesn't seem to make a difference, the pump runs continually regardless and no water comes out of the tap either way.
I get the feeling this may be one of many bodges I have found with the van since getting it, the joys of buying second hand eh

[organicmatter]

They can need a really good suck to get going[FACE WITH STUCK-OUT TONGUE AND WINKING EYE].