Oldest trucks on the road

@Ozdriver , is the steel tank in front of your fuel tanks on the left side an air tank for your air starter?

 

Yes it is, it's isolated from the main system and drops from 120 psi to 110 psi over several weeks.

 

So what do you do if you run out of air? Do you have an electric starter motor as a backup for those situations?

 

No, because the air starter goes in the hole where an electric start goes. It's never run out of air, but I've got an airline that you can hook up to a couple of tyres to get enough air in the tank to start it.
My old KW had air start as well and it ran out a few times when the engine was worn out, but I just hooked up the airline to a couple of tyres. If I'm home I just hook it up to the shop compressor.