When the 544 runs out of fuel:
1. Take the fuel port (Mercedes lingo) cap off and shake the car and listen for sloshing of the three gallons.
2. Remove the sending unit and using a Model T gas gauge (stick) check the gas level.
3. Use an explosion proof light (not a match or electric bulb that get's dropped) a flashlight would be good, and look inside tank.

Right now my tank is out because the poor thing sat so long that the glue that was used to fasten the fitting that holds the pick-up tube came undone. Who would of thought they used glue, I haven't in my 25 years. My plan is to solder it back on. I flooded the removed tank with enough water to make me believe all the gas is gone. Most people would take it to a radiator shop for soldering, but I worry they might have a new guy who might put the thing in wrong and I would only be able to run out the first five gallons. Keith P.
PS. Although the gas gage is pretty hardy, I would handle like it is an expensive part.