When I would turn the key on my Excursion, to warm the glow plugs, I would hear a pumping like sound like a vacuum pump. I am assuming that is the pulse vacuum hub lock solenoid. Well recently I was in a situation to where I needed to switch on the ESOF 4X4. Come to find out that the 4x4 did not engage. I then noticed that the PVH lock solenoid quit making that pumping noise. THen it was intermittent and now not pumping at all.

I am assuming the PVH pump is bad? There is juice at the connection. Any one else have this issue/symptoms?

 

I have a 2001 F350, Vacuum pump working, power to center wire to pvh-solenoid harness whether switch on dash is in 2wd or 4wd. The vacuum goes into pvh-solenoid, but none comes out. I replaced solenoid, and it didn't help.