Kellen,
Look in your owners manual. It's in all likelihood the knob for a gasoline
fired auxiliary heater.
You push it in to activate it, then turn it to control heat output
thermostatically. It makes a real funny humming noise when it runs and man, does it
crank out heat. If you turn the ignition to on (Van does NOT have to be running),
push the button it on and it doesn't come on, it may be because of worn
wiring, or there is a circuit breaker that sits up under the dash roughly behind the
knob on the firewall. It may be popped over and need resetting. Mine was on
my previous 82 westy. Kicked it over and it fired right up. Advice: DO NOT turn
this thing on for the first time without inspecting it first. Check fuel
lines going into it, and the wiring. When you do fire it up, have someone watch
the underside of your van for awhile to make sure that the thing doesn't catch
fire. They're reputedly pretty safe, but I've read stories. Also, it's gonna
stink like hell for awhile til it burns off old dust, oil etc. Do a list search
for "auxiliary heater". There's plenty of info.
If the knob ain't that, then I dunno. Maybe somebody put on a manual choke
and a carbueretor.
Chris Dixon