On the starter RELAY, on the inner fender is the "S" post, its the smaller post, should have a red/blue stripe wire on it
(It is actually a relay, not a solenoid that is on the inner fender, just FYI)
That red/blue wire should have 12volts when key is turned to START, test for that with volt meter or test light grounded to battery negative or a known good ground
If you have a 4 post starter relay it will also have a small "I" post as well, that is not used, must use the "S" post, it WILL have a "S" next to it
If you don't have 12volt on the red/blue wire with key turned to START then thats the problem
Power path is not that involved for this:
12v battery positive----(fusible link)----ignition switch--------clutch or neutral switch------------starter relay "S" post
In 1988 it should be a red/blue wire from ignition switch to starter relay
In 1989 it changed to a pink wire from ignition switch and changed to red/blue at clutch or neutral switch
When you say you are "jumping the solenoid" so you mean you are putting 12volts to "S" post?
If not then try that, it tests if starter relay is working
Starter relays frame must have a good ground for relay to close