Start by checking power to the fuel pumps and swapping the fuel pump relay with an identical known-good relay, since the EEC-controlled relay supplies all three pumps. If that does not restore pressure, listen beside the pumps to see whether the selected in-tank pump and the external pump are running, and use the VIP self-test connector to verify power to the relay. The tank selector switch powers only the gauge and pump for the selected tank.
The owner of a 1989 Ford F-150 straight-six reports intermittent no-start with zero fuel pressure on both tanks and asks whether the external pump or both in-tank pumps are more likely at fault. Experts say the EEC module signals one fuel relay that powers all three pumps, so the relay should be checked or swapped first. If that fails, they recommend checking whether the selected in-tank pump and external pump are running and verifying relay power at the VIP self-test connector.
