w111 glow plug question

[VintageWings]

Hey all - I've not been here in a while but just picked up a 1965 190Dc. I do not (yet) have the W111 manual but have one coming.

The car starts/runs/drives but is a project. I've always wanted a finny and now I have one. Be careful what you wish for!

Here's the issue. It will start on starter fluid but not without - likely due to cold glow plugs. Pulling the plunger to the glow position does not warm the plugs. No power noted at the firewall mounted coil spring so I'm guessing nothing is coming from the switch or potentially a relay - again no manual and no diagrams at the moment. There is continuity from the firewall connection through the glows plugs to ground. Jumping 12v directly to the firewall warms the coil and glow plugs - at least hand warm so I'm guessing I've got a power issue either to or after the plunger. Have not checked to see if when jumped there is a glow at the salt shaker.

Later MBs used a relay. I'm not sure about this one but I'm certain someone here has the answers. I'm off to chase wires but would love any hints/input to save me some time under the dash...

Thanks in advance!