I have a widow friend who was left a bucket truck with a Cat 3126 engine. I cranked the engine and it ran well for a while but one day after it started it went dead and felt like it ran out of fuel. Running two tanks(left tank full and right tank 1/2 full) it used out of the right tank only. I can't understand why the tanks aren't even. This truck has been sitting about 2 years since being used and not used very much in the last 6 years anyway. It will crank on either but goes dead immediately. What should I look for? The lady doesn't have a lot of money and I'm trying to help her out.
Electric or mechanical engine
Does that have a separate fuel transfer pump? A mechanical 3116 has the transfer pump mounted high up and it doesn't suck air very well, especially if there was a tiny bit of water that rusted a pinhole in the bottom of the fuel filter. If there's not fuel coming out of the filter housing if you loosen a line, then prime it with a little air pressure in the tank.
I would check the primary filter first . What brand truck is it in? If the fuel is 2 years old you may have filter issues