[Michael C Henry]

If its a new solinoid ,it should have instructions, if not hope the terminals are marked. They make so many solinoids that all look the same but are different .I've seen solinoids that are for forklifts. The second small terminal is a ground that is connected to the alternater. It works as a starter safety that keeps the starter from activating while the engine is running.But if you ask for a starter relay solinoid for a mid sixties Ford ,the two large (5/16") terminals are (battery)power in and (Starter ) switched Power out,the two small terminals are the trigger or (switch) and (Ignition ) is for resistor bypass that would by pass the Oem resistor that supplies a cut down power to the coil. for a full 12v while cranking. If there is no provision for a ballast resister in the coil power supply then the bypass is not going to gain you anything.On a fiberglass car you will have to run a ground wire from the solinoid metal mountimg bracket to the ground system to operate the electro magnetic switch.
My light blue solinoud was operating just fine when I took the car apart.The first time I tried it after all the work in worked it operated one time and the electro magnet quit, the connection was broken internaly. The solinoids are riveted together and repair is not an option. Heck, they arne't that expensive.My difficultty was finding a color that I liked and the same distances of the mounting bracket to large power in terminal. I ended up with a light grey BW solinoid that had a different way the bracket came off the body but everything worked the same.l