The engine bay appears to be a tangle of hoses and wires, while the fuel door obviously shows a green diesel inlet. Inside, a placard on the dashboard reads "Diesel Fuel Only!". It also says that the truck will have auto stop/start, though it doesn't appear the system is functioning in this truck. The truck also appears to have a unique exhaust tip.
The rumor is that the new 3.0-liter V6 diesel engine comes courtesy of Jaguar Land Rover. The photos here reveal a diesel-powered Land Rover Range Rover Sport following the diesel Ford, further cementing the validity of this rumor. In the Range Rover, this engine makes 254 horsepower and 440 lb-ft of torque. That's slightly more than the 240 hp and 420 lb-ft of torque made by the Ram EcoDiesel.
As you can see in the photos, a blurry, phantom-like engineer is working away under the hood. Our photographer said a wiring problem sidelined the truck, meaning Ford still has some kinks to work out before the engine is ready. Expect a full reveal within the next few months.