If bridging the starter solenoid results in the starter cranking and the engine starting, surely the starter solenoid is the culprit.

How do you retension springs, if thay have sagged, ie their rate has changed, then the spring material properties have become permanently changed.

If the solenoid is the culprit then even bridging it will not let it kick in. Remember, you don't bypass it, you only close cuircuit, like you would by presing the starter button.
As mentioned in my previous email, when you press the starter it sends the current to the solenoid in order to swing the starter, but if the wire has become coroded, the internal resistance of the wire prevents it from delivering the sufficient amount of current for it to triger the starting. I do not say that this is the solution, but it is one of the posible problems that has to be checked and eliminated before searching further for the solutuion.

Re. Resetting springs. We have engineering shops here that reset the spring to its factory intended load set and then retemper them.
Good as new.

I assumed m4rkymark is measuring 11.5 volts at the solenoid from the start button, in which case the relay should pull in with not problem. The main wiring from the battery to the starter motor must be ok otherwise the starter motor would not turn when he bridged the solenoid main terminals.

After further research, I stand corrected, a sagged spring will retain its original spring rate and therefore can be reset to original length. I would add that a spring that shows repeated changes in free length with time should be replaced and not reset.

magg wrote:I assumed m4rkymark is measuring 11.5 volts at the solenoid from the start button, in which case the relay should pull in with not problem. The main wiring from the battery to the starter motor must be ok otherwise the starter motor would not turn when he bridged the solenoid main terminals.

After further research, I stand corrected, a sagged spring will retain its original spring rate and therefore can be reset to original length. I would add that a spring that shows repeated changes in free length with time should be replaced and not reset.

Thank you for your comment.
I am not an expert nor do I claim to be, but I have been around the block a couple of times.
Thats what we are here for hey, to help each other out and learn from each other.
Shared knowledge is the greatest wealth a community can aquire.