As much of an improvement as the FDM system was over the previous EFI pump system, it's still subject to failures, mostly related to fuel varnish building up on its internal surfaces. When it builds up in the level sender, it causes the gauge to peg FULL, as any open circuit would (high resistance). If diagnosis shows the fault to be inside the tank, the sender can sometimes be cleaned & returned to service for a fraction of the cost of a new sender. In either case, a new O-ring is required between the pump mounting plate & the tank.
Instructions for removing the FDM can be found in these albums' captions:
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-Bronco ONLY
See also:
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