Recently we have been having to turn the key back from the start position to the on position when we start the van. Well now, it’s stuck in the on position and will only click when moved to start position.

We purchased a new lock cylinder thinking that was the issue but was not. We can visually see the slide moving back a forth inside the casing so the tumbler is turning just not disengaging from on position nor will it start.

we can start the van by jumping the starter.

could this be the ignition switch?

 

The ignition switch actuator is broken

 

The ignition key lock cylinder engages this slot seen when it is removed from the column:



That piece above rotates by the key lock cylinder which in turn moves the white part here inside the column which has the actual electrical ignition switch pin inserted moving its contacts along a straight line to complete a circuit for starting, accessory etc.



From you somewhat unclear description I would guess something inside the column has broke. You can test that by removing the larger white block shown above and moving the pin to its various locations checking to see it is functioning properly. If manually moving it through its positions you can achieve the start, run and accessory functions it is good.

When that part is removed and with the key lock cylinder installed move it through its positions watching the small piece with hole move (or not). If it does move with the key cylinder's rotation then the issue might be just the actual switch itself.

With the column still in place the ignition switch looks like this as installed and connected to the chassis wiring:



The color of switch body might change due the van's year but its the same part shown in the previous photo as white, this one in green.

Hope this helps.