Grounds, grounds, grounds...

Okay... regardless of the electrical system you are putting in any car, problems with grounds account for over 90% of any of the issues that you may have. This is true for our ISIS Intelligent Multiplex System, any EFI controller, stereos, amplifiers, even traditional relays. There are few things more important when wiring a car than your connection to ground.

This starts with something fundamental: a good metal-to-metal connection. When creating a ground connection, make sure that all of the metal surfaces are clear and clean. This means removing any rust, paint, powder coat, clear coat that may get in the way.

Second, you have to protect these joints from corrosion. A good ground today, may degrade over time as the junctions get dirty and corrode from normal driving.

Finally, remember that what goes in must come out. Make sure that your ground connections are sized to handle current. I mentioned before that the most common mistake that guys make when wiring their cars is to under size the cable from the battery to the starter. Well, the second most common is to under size their ground cable. A OO gauge wire from the positive side of the battery to the starter is useless if the negative terminal connects to the chassis through a 6-gauge wire. Same thing when you think about ground straps from the engine block to the chassis.

Remember that that ground has to carry the alternator current plus the starter current. A 14-gauge wire between the block and the chassis will measure good continuity with a meter but will cause a lot of problems when you crank the motor.

Keep an eye on the ISIS Power Reference Library. We're creating a few tutorials on grounds. These will have our recommendations on where to put them, how to prepare the surfaces, the types of hardware to use and how to size the cables. I'll post them up on the blog too when they are done.