Hi, I made a small modular engine, just one cylinder and one cranck shaft.

With a small tank and and air filter it can work under water (in any condition) and still runing when fuel run out (only if the tank is spawend with 100% diesel. Withe less the 100% or if a small engine consume some diesel that modular engine will stop when run out of fuel).

https://steamcommunity.com/sharedfiles/filedetails/?id=2612458259