External Starter Relay Mod
That is an external starter relay that can be added to fix a bad start issue with the old wiring. You should be able to bypass the starter relay by shorting out the two contacts with an insulated screwdriver to test the relay. If it starts, then you need a new relay. You will need to do a search for the item number since it is not OEM for this vehicle. If it is a stick, make sure you have it in neutral with the parking brake up. I did the mod on my vehicle and it now it starts very quickly. I used to have to turn the key and have someone hit the starter with a rod.
A quick search for the 22re starter mod will show you some information on this.