The littlest fire truck.
Quite possibly, this picture shows two air cooled VWs, as the air cooled VW flat 4 engine was a popular power plant for portable fire pumps due to its good power to weight ratio and ruggedness.
I’m sure you’re right, all the pumps I’ve ever seen were the VW industrial spec flatfour.
The industrial version of that motor is ideal for such mobile applications, entirely self contained, needs no battery due to magneto ignition, minimal risk of failure of the cooling system (no freezing, no leaking, as in water cooled engines), the only accessory it absolutely requires is a fuel tank. And its ruggedness is legendary, as long as you keep the fuel tank topped up, it’ll run under load for days continuously. Its only real downside is its annoying reluctance to start when warm.
