Cat D4G Air in Fuel System

I have a 2005 Cat D4G with the Mitsubishi Engine. Have removed the Fuel Tank a few years ago to have it cleaned and lined because of rust problems. Use to have all kinds of problems keeping it running until I did that. The symptom before I had the tank cleaned was it seamed to get air starting in the fuel seperator in the rear and then air would get into the secondary filter. Figured it was sediment in the tank from being rusty. Anyways for two years after cleaning the tank no problems....

Cat D4G Air in Fuel System

Cat D4G Air in Fuel System