[Spruce]

Update- went to the webasto service agent yesterday,hooked the system up to a computer and it showed flame failure had occurred 7 times.Done a few tests and everything working as it should now, it seems that air bubbles in the diesel pipe caused the problem.
Thanks to everybody for their advice,much appreciated

I haven't got a diesel heater myself, but have got a webasto air heater which works on a similar heating principal but heats the air rather than water.

If the problem was air bubbles then you need to find out how the fuel pipe was connected to the fuel tank. If you/they have tapped into the fuel pump return to the tank like mine is  then you will need to make sure that you don't let the diesel in the tank drop below a quarter. The diesel return pipe to the tank from the pump doesn't go all the way to the bottom of the tank.

If they have fitted a separate fuel pick up tube into the tank, then Webasto also advise the fitter to cut the tube off about 3/4 of the way down. The reason behind this is two fold.
1. you don't want dirt from the bottom of the tank sucked up into your heater and
2. you don't want the heater to drain the tank and not leave you enough fuel to get to the nearest garage. (Remember that these instructions are for Webastos fitted worldwide and fuel stations are not as numerous in some places as they are here.

Spruce

[KS Cleaning]

Yes your right spruce,that's what the webasto engineer said,don't let the tank go below quarter full,even if it is just a wee bit below thiis level and you are sitting on a steep hill that could be enough to let the air in.Will defo be makin sure I have at least a quarter tank from now on.