I do not know how the regulator in the alternator was faulty as the regulation is done by the ECU....there is no regulator in the alternator. That is not the point though...here are some suggestions:
Check the cable that goes from the engine to the chassis is clean and tight on both ends.
Check the battery connections are clean and tight and the negative cable going to the chassis is clean and tight.
There have been a lot of reports of there being a problem in the ignition switch area...escpecially on older KJs.
What happens is that there is a small rectangular metal or plastic bar that goes from the tumbler of the ignition switch to actually rotate the ignition switch when you turn ignition ON or START....this small bar breaks and is unable to rotate the ignition switch. There is a link I will try to find for you on this matter....the dealers say that the broken piece is not available ....you have to replace the whole steering column assembly. This is not true...as the link will show you....the individual part can be purchased...at least in the USA!
Remove the two plastic covers covering the steering column...you will need a small male Torx bit to remove two screws from underneath. You will see the ignition switch....it has all the wires coming out of it and is attached to the steering column by another, smaller Torx screw (later KJ models have a special security type Torx screw with a centre protusion...yours should be standard).
Remove this small Torx screw and pull the ignition switch off. You should now see the small rectangular bar of plastic or aluminium that operates the switch....the bar is hollow inside and has a small sliver of plastic protuding that operates a small contact when the key is pressed in...this "beeps" you when you leave the key in the ignition. Hopefully this rectangular bar is not broken. If it is...you can over ride the starting issue by putting the key in the ignition and turning it...so as to unlock the steering and then turn the ignition switch with a small flat screwdriver.
There are several fuses you can check first...in the engine bay and on the side of the dash and there is a starter relay in the engine bay that you can swap out with another relay to check if it is the relay.
Edit to add...here is the link to ignition switch problem.
Edit to add again...clicking on this link does not work for me....but typing in the whole URL as shown does work for me??