Damn, and here I was trying everything except that :P
Thanks. I got thrown off by the fact that the data drives let you insert them directly from held and was trying the same thing.
The gas output on the side of the cremator won't let me put a gas can in it to fill them up. Using an empty gas can I get the "Gas tanks is empty." error message (even though the cremator has 150 gas in it). Using a semi-full gas tank gives me a "Use gas tanks on the fuel tanks of the vehicle/device." info message.