Problem: My '89's fuel pump started cutting out intermittently during hard acceleration (~5200 RPM) during auto-xing. The problem progressed to the point it started cutting out at Interstate speeds. The engine would just lose power/quit and I'd coast to a stop, restart the car on the first of second try, and resume driving. It was both annoying and dangerous.

Investigation: I first checked fuel, air, and spark to try to isolate the problem. After determining that there were no vacuum leaks leaning out the A/F mixture, I turned to the spark side of the combustion equation. Both the timing and distributor checkout fine. I turned to the fuel pump and checked the voltage from the fuel pump relay through the fuse box on to the tank connection. Full voltage was getting through the wiring harness all the way to the fuel pump/tank sender.

Solution: I decided that the fuel pump must be giving out after 104K miles, so I purchased a new one along with the necessary fuel pump strainer sock, and gas tank gasket. After pulling out the tank sender/fuel pump assembly, I was surprised to find that the internal wiring for the pump and ground were obviously damaged (by ethanol ?) (see pictures below). I measured the continuity between the ground and the fuel pump positive lead. Just moving the sender/fuel pump assembly could break the continuity between the two. Ended up buying a new ACDelco sender assembly specifically designed to withstand E85 and attached the fuel pump to correct the problem.

Just posting this in case someone experiences the same problem in the future.