these type are still called starter solenoids even though they aren't mounted on the starter...
cut back some of the insulation on the negative wire and make sure it isn't corroded up inside the wire
i know what they are called, but they are heavy duty relay's.
a solenoid has an iron core that moves to either make electrical contact (like a starter solenoid), or to actuate something (like a shift solenoid) a relay is only for electrical contact and moves a metal arm.
i was just sayin... lol