1999 (early build) F250 Super Duty Extended Cab 4X4 diesel / automatic. Recently bought the truck used. Lots of additional wiring had been added over the years of uncertain purpose. The current owner, a recent widow, is unable to address my wiring questions. So...Inside the frame beneath the the drivers side and just aft of the high pressure fuel pump is an odd device that I need help identifying. See photos. It appears to be an add on solenoid valve. About 2" long, 1" diameter with a single control wire routed up into the dash board. Two 1/4" rubber hoses are attached with screw type SS band clamps. Hence my suspicion that it is after market as Ford does not routinely use these. One hose terminates, simply open, about 12" back. The opposite hose is routed forward into the nether-lands of the engine compartment. In the process of tracing the add on wiring I found the wire to this thing frayed, bare copper touching the frame. I cut away the wire leaving the valve inoperable. I expected problems as a result. Nothing. The truck seems to operate just fine (now 2500 miles) without an issue.

Any clues?

 

Power it up and see what sparks.

 

Clean it and see if you can find a part number.