Been working on this for too long and need help.
1993 D130 with a 3.5V8
I only get fast clicking at the starter. It never turns over the engine.

Here is what has been done.
-new battery
-new battery terminal connections
-new positive lead from battery to starter
-ground cleaned at battery to chassis, and engine block to chassis
-New starter
-added ground, starter solenoid to chassis
-new starter relay
Power checked at relay
-12.7v on hot line in
-12.7v on crank line from starter
-12.7 on line out to solenoid,,,and also checked at the female spade connector at solenoid.
- relay clicking and power switching to out line to solenoid so ground at relay presumed good.

I have turned the engine over with a large spanner and there is normal resistance.... so not seized.

What am I missing??

Sounds like the same as the problem I had, basically get the starter internals kit (about £12 of eBay) and remove the starter and replace the terminals inside, easy job should sort it out

Client killed the first starter. Bought a britpat and got clicking.
After much fussing around, bought a better starter.
Same result.