My 1980 series III came with a big propane tank in tank in the back, and a Lovato system for switching between gasoline and propane fuel. I think it was original equipment, the vehicle was Australian military and hasn't been modified. I never paid much attention to the propane hardware, and recently decided to remove the propane tank, since it takes up a lot of space. Imagine my surprise (and fascination) when it turned out the tank was still full of propane! So I started taking a look at the dual fuel system. Looks to be well built, and intact. A small controller (marked Lovato) mounted under the dashboard has a switch to select fuel.

Naturally I'm now trying to resurrect the old propane system.. with a fire extinguisher near at hand. A solenoid valve under the hood controls the supply of propane to the carburetor air intake. When I apply 12V to the solenoid, a burst of propane is released. But the control system isn't working. When I set the Lovato switch to propane, the (gasoline) fuel pump shuts off, as it should, the engine continues to run for a minute on residual gasoline in the carb, but the solenoid does not open to release the flow of propane, so the engine stops. Is anyone familiar with this system? I'd appreciate any tips. Am wondering if the solenoid is proportional or on/off (i.e. how is the mixture controlled rich vs. lean?)