I know someone will correct me if I am wrong. but I THINK the chevy 6.2 had an engine driven mechanical pump? (I don`t remember an electric pump on my `88 pace arrow) which if worn will tend to loose "draw" as the fuel level drops, add in a dirty filter and you may have the answer to your problem?
another consideration, is the fuel tank air vent Blocked. if so the tank will have a negative pressure and tend to "suck back" on the supply line, competing against the fuel pump?
You may have a problem with the fuel pick-up pipe in the fuel tank. Some manufactururs fit a filter at the base of the pipe. The bottome of the filter becomes blocked, this would then cause your problem when you are low on fuel.
For what it's worth, i have virtually the same vehicle as you. Although i have not had this problem,sometimes when filling up during a trip i have noticed a vacuum when undoing the filler cap.Maybe it's the vent in the cap blocked.
I have experienced this with the Scania trucks that I ran we found several causes.
Filter at the bottom of the pickup pipe in the tank blocked.
Some clever previous owner had taken the pipe out and shortened it so as not to pick up the crap in the bottom of the tank
We have also had a small blob of sealant or the like that floats just below the surface and thus when diesel level is low this will sometimes get stuck in the pickup pipe if there is no filter. This was a nightmare to trace as when you take the pickup pipe out you release the suction and the little blob drops out again:Angry::Angry:
Another problem we encountered was the filter at the end of the pick up pipe had rubbed over years on the bottom of the tank so much that the flat bottom had worn through at the edge to form a sort of flap which would sometimes swing up to block or restrict the pickup pipe.