Good day! Just came across this post. I'm sure you have your answer regarding the blue knob.....but just in case ou don't, here goes. With my truck (a 1987 Land Rover Santana 109, 2.25L diesel, LT85 5-spd gearbox, 5 doors) has the same knob (but in green). It also has two fuel tanks. One is under the passenger seat and accessed by flipping the passenger seat forward and sliding out a tray-like cover. The other is in the rear of the vehicle, hung between the frame and crossmembers. The knob lets you determine which tank to pull from. The switch on the dash has three positions (up, middle, and down). up and down indictae the fuel level in each seperate tank. When the switch is in the middle position, it is has no power and displys nothing. Good luck, and it's always good to see another Spanish Land Rover on the road....despite what the Solihull enthusiastis will tell you......
