that is the model number,,,I was asking for the serial number, but thanks, and now you have answered the question that having the serial number would have answered, (which system and version your truck has)
22710 fu460 is what Mitsubishi forklifts and Cat Lifttrucks calls 'the injector driver', it sends the pulsed signal to the primary/main injector. it's functions are inside the ECM on newer that 2007 machines. I still think it is the relays, as long as the key switch and it's wires are good

Mpl02a25lv

You are correct. Has injector in throttle assembly.
Dash and ignition switch work fine. When i disconnect certain items such as tps or maf or an ignition coil I was able to get a code to pop up for that item. The. I'd clear it out. Attempt to start and may hear a sputter. But no codes. On occasion it will start. But eventually die. Not sure if it dies due to warm up or not. Would think it'd throw a code for crank sensor but you present a good point.

Question: what's the switch module suppose to do? Control ignition? Part number 22710 fu460

serial number always helps....
since this unit normally shows set codes in the dash hour meter display, and you don't see them, check the key switch and wiring to the key switch (something that shuts down the truck normally, so that the computer does not 'see' anything out of the usual).
Also you should consider -replacing- all the relays in the relay box (one at a time, if you want, but replace with known good) you may have moved the bad relay to another spot that the truck needs a good relay in to run. it takes at least 3 of the relays all to work (and those 3 may no be right next to each other) for the truck to run.
Just a minor correction that probably does not have anything to do with your problem here and now, assuming this is a LPG powered truck, this unit DOES (or should/did when it left the factory) have 'fuel injectors', just not multi-point fuel injectors, this one has 2 fuel injectors (main or primary, and assistant or helper) mounted in the throttle body.
I would suggest biting the bullet ($) and getting someone who can hook the laptop up to check the sensors, rather than fighting blindly.
this truck NEEDS to see the crankshaft turn before it ever gets spark, and the starter motor turning but the crank sensor not sending a signal to the computer may cause no spark and no codes, since it never thinks the engine is actually turning (the computer does not recognize the engine rpm except from the crank sensor, and does not control the starter cranking.