When I bought my 91 4runner a/t, it had a bypass switch to start the engine, i rewired it and most of the time it starts right up, but i think the switch is going out. Is there a way to rebuild the switch or should i just get a new one entirely?

 

You think the ignition switch is going, or your bypass switch is? Either way generally switches are non serviceable items. You can ensure that the external contacts are clean but beyond that it is replacement time. I suggest (regarding either switch) that you use a relay to handle the IGG1 current (starter solenoid current)...I'm not sure if 91's came factory with one or not. If it didn't wire one in (it may fix your issue) or if it does test it or replace it before replacing the switch...it may in fact be your issue.

Get your multimeter out and run a resistance test across all terminals of your ignition switch...It will identify whether it is the issue or something else in the system...