[Willie Krash]

If one of the big terminals is marked Batt. on the sol. body, then Bob C is correct.
The diagram Mike shows is a marine set up. Normally the base is ground. If it is purely automotive it should be....Use 1960's mustang starter relays.
Jump (as you did) again and instead of a click look at the wire as you touch it to the S term. It is about a 2 1/2 amp draw and a nice blue spark. If that is present it means your ground is intact. If no spark go from the relay base right to the engine or a good grd, batt if you can get there. retest.
Look at the two #10 studs. Most likely marked S and R(i). R is for resistor by-pass.
To mix it up some manufactures use S/R bodies and R is a ground. Saves money.
For me two #12 jumper wires with alligator clips belong in my "A" tool box.
Oh yes, make sure it out of gear. Kinda important.