The SMC VXD2140 is an air valve operated by a pilot valve, using the 12VDC coil to move an armature, that opens / closes a pilot valve, moving a diaphragm to open / close the air flow.
My read is that the stuck-open valve is because the pilot is stuck open, or not sealing shut.
In your pictures, the small black circle inside the spring-loaded tan disc is the shut off seal. There is a little crud on the black, but it looks insufficient to me to prevent sealing the shutoff.
Does the spring-loaded ribbed armature (9) slide freely inside the tube assembly (8)?
The corrosion on the interior of the coil assembly should not cause the stuck-open problem. That interior bore does not have moving parts. That interior bore exists so magnetic flux (when the coil is energized) to be transmitted to the armature, causing the armature to move, opening the pilot valve.
According to the specification sheet, the VXD2140-04 is rated for 1.0 MPa (145.0 PSI) operating pressure.
So if the armature and spring are put into the tube, the tube is clipped onto the coil, then does the armature suck in hard when the coil is energized?
(Remember, the spring will force the armature out when the coil is unpowered, so wear safety glasses and point it in a safe direction.)
It looks like the pilot valve seal is bad after all.
Note that in the completed assemply the armature moves a very small distance in the tube, so the click might be quiet. The tube cross section shows a paramagnetic slug at the end (in the center, near 13), used to retain the assembly and to shape the electromagnetic field.
That cross section shows the small gap that the armature moves, between the paramagnetic slug and the armature (9).
It may be that the coil has gone weak, or that the seal has gone bad, but safely energizing the coil on the loose parts is the best way to ID the bad part.
Note that in the completed assemply the armature moves a very small distance in the tube, so the click might be quiet. The tube cross section shows a paramagnetic slug at the end (in the center, near 13), used to retain the assembly and to shape the electromagnetic field.
That cross section shows the small gap that the armature moves, between the paramagnetic slug and the armature (9).
It may be that the coil has gone weak, or that the seal has gone bad, but safely energizing the coil on the loose parts is the best way to ID the bad part.
It is clear just by audibly testing/activating the solenoid that there is a problem. Being that everything is clean/free to move/intact, I am pretty positive its just a problematic coil. I’m gonna save it for parts…
