From The Bell 206 Book:
As fuel to the engine can only come from the main tank, a problem in the transfer mechanism (usually from contamination) can mean fuel being trapped and unusable in the front tanks. Cockpit indications are fuel quantity and pressure gauges, 2 boost pump warning lights and a fuel low light. The quantity gauge derives its signal from 3 transmitters, one being in the forward tank, so it will always read total fuel available, but, as the Fuel Low probe is only in the main tank, you can get a fuel low indication with an apparently plentiful fuel load. In fact, when the fuel transfer valves are stuck open (a grain of sand will do), the engine will quit at 200 lbs, or even as high as 240 lbs (from pilot experience).
If you remember nothing else about a LongRanger fuel system, remember this…………
WHATEVER THE FUEL QUANTITY INDICATION -
IF THE FUEL LOW LIGHT ILLUMINATES:
BELIEVE IT,
LAND,
AND CONTACT AN ENGINEER