I don't actually have a problem here, I am just wondering, on my '98 xpress 300, on the left side above the clutch cover, there is the fuel selector dial. Off, Run, and res. What is the res. setting for? anybody know? I'm pretty sure its not a reserve fuel tank, as in all the work I have done to this thing (including rebuilding the powertrain), I have never noticed one. Something is hooked up to that spot on the switch though, and I'm just curious as to what.

 

It's your reserve. The on setting gets the fuel a little higher in the tank. When that runs out reserve draws the rest of the fuel from lower in the tank.