Me again…this truck #%#%*!!!!!

My tri axle has two of those fuel filters also. Don't think I would change them. That's the way the truck came.

 

Maybe I would change out the primer pump if you haven't already.

 

Hopefully that's the problem. As for the fuel filters my Detroit 60 has two of them, primary and secondary side by side on the drivers side. That's the way mine came.

 

If the primer pump is bad and allowing air in the system it doesn't matter that you hadn't been using it. If its in the truck and bad it will allow air in. Regardless of the last time you used it. I'm not saying that's the problem but clarifying.

How about a picture of the 2 fuel filters on the truck and where they are mounted.

 

look at the filter while its running and see if u can spot bubbles and then check inside the tanks for bubbles and that will tell u if ur pulling air in the system

 

something else to check is if u have the filter like in the big picture the big black ring that secures the clear globe to the base might be cross threaded. when u put it on after a filter change it will screw down easy and when u tighten it with the circular wrench that fits around the big ring it should only be about a quarter turn to get tight. if u have to keep screwing it to get tight its probably cross threaded and then when u tighten it like that sometimes it will seal and sometimes it wont. theyre easy to crossthread because ur working against the spring on top of the filter. once its crossthreaded it usually wont line back up straight again.