1993 F250 7.5L. Just left for vacation, stopped at the big yellow candy store in Jordan, MN. When I stepped on the parking brake with truck running from the "P" position the pedal went to the floor and felt "loose". I turned the truck off and tried again and the PB works as normal. Also now works with engine running or engine off. Any ideas?

 

The engine running or not has absolutely nothing to do with the parking brake. It is a mechanical cable operated system. Sounds to me like the pedal assembly is going bad.

 

second on the assembly going bad, but also check to make sure cable is tight and is ADJUSTED.

many people do drumb brakes and dont adjust that cable

 

This is a known problem with these trucks and there is a recall for it. For whatever reason the pawl for the automatic parking brake adjuster fails to engage with the sector gear and that is why the pedal went to the floor. Fords fix is to install a wedge that prevents the pawl from disengaging from the sector gear. The auto adjust does not work with the wedge installed. There is a TSB that tells to remove the wedge then apply and release the parking brake six times to adjust them reinstall the wedge.

 

ford recall 94s91

The problem seems to happen during fast pedal application.

 

First, check to make sure you didn't break a rear cable. When one breaks, the pedal will go to/near the floor. The pedal will self-adjust on the next activation.