T3 starting issue

[grumble]

Just got back from a weekend away and had an issue starting again. 
Last time it happened was twice going to Busstop last Easter. 
Once at Broken Hill and once just outside of Strathalbyn (on the Murray - can’t remember name)

First time it happened was a couple of years ago on our northern NSW trip up Walcha way. 

I faffed around with hitting the solenoid, replacing key switch, cable tieing plug cables so they don’t move
Narrowed it down to the starter solenoid wire. 

Turn the key and I get power to the solenoid terminal. 
But won’t fire. 

If I replace the wire and take a “hot wire” from the alternator - fire right up. 

I have changed key switch and it’s not that. 

It is very intermittent. 
Only happened 5 times but all in the last 3(?) years

I haven’t replaced the spade connection. 
That will be my first job. 

If it’s not that I’m not sure what to do. 
If it’s the plug on the key switch I doubt I can get a new one. 
“If” I can get a second hand one - I will need to splice it in. 

Maybe just run a new solenoid wire?
Anyone done that?
Where does the loom run?

Barry do you have 12 volts at the solenoid wire when it happens? A possibility may be the inhibitor switch, try moving the lever back or forward when it won't start and reset the switch if this fixes the problem. My auto had a fit like this and resetting the switch rectified it. Another possible cure is to fit a relay to the solenoid wire as this will give a direct 12v to the solenoid eliminating any voltage drop in the circuit. My gut feel is the inhibitor switch adjustment.