Regarding item (4):
Is 15 amps the right number? According to this diagram, the wire appears to be 15 Amp. Is that correct?
"Always size the fuse / breaker to the cable"
- I'm not endorsing 15 Amps as being the right number - I've only glanced over your questions to answer some.. but - 15A cable, 15A fuse. Where you use two sizes of cable, 15A for some, 10A for some, then at most, a 10A fuse.
Regarding item (6):
How exactly does one find a ground? I never understood this in grade school, and to this day I am still confused.
"In DC circuits, ground is the negative terminal. In car electrics, typically (check yourself) - the ground terminal of the battery (negative) is typically connected to the body, and so the entire body is connected to the ground of the battery. Some can be positive though, so Check!"
Or what I'd do is find black and check it has continuity through to ground - and that is what I'd use!
Regarding item (7):
I was thinking of putting spade connectors in when I splice into the wire. That way, if something goes wrong, I can just unplug the relay and slip the two ends of the injector signal wire back into place.
Would this work or am I missing something?
"Wire the relay fail on. That is, your relay has 5 wires, the coil on that you switch, and a Normally Closed side, and a Normally Open side.
Wire your circuit such that when you switch the relay "ON", the circuit to the injectors are broken, when you switch it off, or, for example, the wire is broken, the injectors just keep going as the relay is OFF."
There's stacks of info on automotive 5 pole relays on the net
