Up to 1962 the split screen van had no petrol gauge but was fitted with a reserve tap under the petrol tank. By pulling a lever in the cabin, a cable makes the tap switch between 2 tubes. One for normal use and one for the reserve. On the later vans the reserve tap was removed and a gauge fitted.
The previous owner told me that he had replaced the tank in order to have a gauge. He had put a speedometer with petrol gauge but it never really worked. When I fill up, the gauge goes up but registers empty after about 5 miles.
The first thing to do was to check if I had a reserve tank or not. I tried to follow the cable from the lever in the cabin and under the petrol tank I have found this (see picture) it looks like I have got a reserve tap. But does it work?
Reserve tap under the petrol tank.
Then the next thing to do is to empty the tank in order to see if the reserve works, so I let it run dry. To monitor how empty the tank was I disconnected the wire from the gauge and I have put an Ohm meter on the electric sensor on the tank.
The petrol finally run out and it was the moment of truth. I pulled the reserve lever and after a few tries, in order to refill the carburator, the van started again. YES.... The reserve works. So the question now is, how come I have a petrol tank with a reserve AND a petrol gauge? But hey....
Being sure the petrol tank was empty I then recorded the resistance equivalent to the empty tank and as we can see in the picture the value was 70.2 ohms.
It was now time to use the reserve and go to the petrol station to refill. Hope I'm gonna have enough..
Back home I measured it again to see what the resistance is corresponding to a full tank. This value was 14.3 Ohms.
So that's it, I know a bit more now. I will be able to buy an external fuel gauge 70 ohms empty - 14 ohms full.