Went out and tried starting my4020.ot ran 5 min then quit and wouldn't start. Tracked down to what I thought was an injector pump problem. Had it rebuild and still wont start. Not getting fuel threw the return line and seems to be a whole loy of pressure building up In the fuel filters and tje main fuel line from the filters to the pump itself. that was same issue I had before pump rebuild and im fairly certain I got the air out and timing correct. 67 4020 diesel with roosa pump.thanks for any help im stumped here and not anybody left in my area that knows how to work on these 4020s anymore I can talk to