Question: Why didn't Mace want to tell Stringfellow Hawke where St. John is? Did Dunkirk tell him not to, or was he working with the people who were holding St. John prisoner?
Answer: I don't think it's ever explained why Mac refused to tell Hawke where St. John is.
Question: Hawk asks Mace where St. John is both before he gets knocked out and sent to the desert, and in the scene where Mace is demonstrating the helicopter they stole capabilities. But Mace won't tell him. Why not just capture Mace and water-board him to force him to tell him where St. John is? Or inject a truth serum into Mace?
Answer: No truth serum has proven to make a person tell the truth. Regarding capturing Mace, and forcing him to tell him where St. John is by water boarding him, People subject to torment such as water boarding are not likely to tell the truth, so Mace would probably lie.
Chosen answer: Archangel and the Firm provided fuel and armaments. Dom and Hawke would have had to transport them to the lair to refuel and rearm.
Grumpy Scot