1985 426 cat with perkins engine. it will run great for days and days. months even. then all of the sudden (usually at the most inopportune time) it will die. I bleed the fuel system and crank it over for about 5 minutes and it will start. then for the next 2 hours it will get little air bubbles working through the system that make it die and have to crank it for 5 min to get it going again. It's hard on the starter.. I have replaced the fuel filter, cleaned the glass water trap, blown out all the lines, cleaned the screen in top of the lift pump. the previous owner replaced the lift pump. the only thing I can think of is maybe the lines in the tank. I blew air through the breather line. and also through the line from the glass water trap back into the tank to make sure it's clear but could it be loose inside the tank picking up air? I can't see how they come off. there is just a block of metal welded to the tank with pickup and return line going into it in the back left hand corner. do those lines come out somehow?
I have seen the lines inside the tank crack before near the top. We had chased it with the same symptoms as yours for a couple of weeks. The final call came in and the tube broke off finishing it. Does it happen at different fuel levels when it dies?
it stands out in my mind that once when It happened I had about 1/4 tank of fuel and was on an extreme hill sort of jerking the machine around pulling stumps. at the time I thought maybe it was sloshing and got some air into it. last week when it happened I had 1/2 tank of fuel. I have never had it happen when it was topped up full. how do you access the lines? will it be evident once I have the tank off?