Talking about using acetylene as start aid for a diesel can be a very bad thing but it can be done the problem is the acetylene's explosive reaction to high pressures. Just a whiff OK but flood the breather and watch the head bolts stretch or a con rod pretzel like too much nitrous in a street racer.
Propane is not as bad but still dicey same with starting fluid the only engines that were actually designed to be started with ether was the old 2 stroke Detroit's they even had a port or a chamber where you could place ether balls an puncture them to get the engine to start ether balls looked a little like paint balls only larger. Drop one in slam the lid and spin the engine over if you didn't get white smoke , do it again soon it would start and eventually it would become so addicted to the stuff you advanced to using cans of starting fluid.
Once while I had my old Dodge welding rig I ran out of gas way down around Langtree, South of Ozona Tx. my welder was diesel and the truck was gas I laid the tip of my torch in the throat of the carb used a wire to spin the engine over then turned on the act. until it started I adjusted the flow until the engine was running around 2000 RPM closed the hood to the safety catch then drove the 45 miles to the nearest gas station, dodgy at best but better than walking in the middle of the night.
My dad was working on an old Autocar that had an air starter we had several inches of snow on the ground went out to start it up whirrll went the starter but no start rolled the air compressor out filled the start tank gave it another go still no go dad came out with a shop rag soaked in gasoline, shoved it in the breather and said start it boy. I gave it a whirll this time it caught and ran. My dad said a little bit of ethel will do it every time always remember that son.
Todays water gas doesn't work quite as well but I've found that the premix chain saw fuel you spent 20.00 a qt for works great pour a little on a rag and shove it in the breather tube the vapors will be enough to kick off an older engine that doesn't have an intake warmer if you have those it must be disconnected or risk exploding the intake don't ask me how I learned this.