Please help! Identify this electrical part

Ok I checked rockauto.com and I can now identify the part as the starter solenoid. But is there a reason as to why the red wire is bolted/attached to the area I circled and why in God's name does it trace to the positive lead?   

It's no mystery why it's arcing when you hook up the positive cable,  you're hooking up the positive cable to a ground.  If that small red wire is wired to ground, it shouldn't be.

The red wire could be a constant 12v hot line to feed a relay, sound system or something along those lines. If it is it certainly should be fused as close to the starter relay/starter solenoid as possible. Under no circumstances should it go to ground. This would be a direct short and the wire would have burned up the instant you connect the battery.

By the way, that's NOT a negative lead going to the starter. It's a POSITIVE lead. The starter grounds back through the engine block to the negative battery cable. The starter relay mounting bracket is the ground path for the solenoid's internal magnetic coil.

You may want to make sure that the old starter relay isn't shorted between the two large side terminals. Check these for no continuity from side to side. There should only be continuity when its energized by turning the ignition switch to start. It's not uncommon for these to stick or for the internal contacts to weld themselves together.

The negative battery cable should be attached securely to the engine block and the positive cable goes to the starter relay closest to the battery. The opposite terminal goes down to the starter. The battery terminal of the relay is also the input connecting point for the main car electrical harness feed as well as for the output wire from the alternator. It's not unusual to also use this terminal for an accessory feed for aftermarket stereos, lighting, etc.

There should also be a engine to body ground jumper that completes the body ground path to the engine and consequently back to the negative terminal of the battery through the engine block. On V8 cars it's at the passenger side motor mount bracket. It electrically ties the engine cross member to the block. It's a heavy black wire but not as heavy as the battery cables.

Edited by george w - Dec/03/2016 at 5:38am

Thanks for your detailed reply George w. Much obliged