Electrical Basics and Automotive Grounding Systems



This is one of the new battery terminals I installed to replace the old corroded ones.  (Try not to let the shiny blow-off valve in the background distract you.)

Now that we have the main ground installed, it’s time to start grounding other things in the vehicle.  Here’s a list of some of the things you may want to ground:

• Engine block
• Alternator
• Ignition System or box (like an MSD unit)
• Electrical sensor reference ground*
• Computer/ECU ground
• Firewall
• Fuel pump

 *The reference ground is where most of the electrical sensors in your car are grounded.  To figure out where this is, consult a service manual or ask around on a forum specific to your vehicle.  On my car, the reference ground is where the fuel rail bolts to the cylinder head and intake manifold.  Supplementing this ground gives your ECU clearer signals from its various sensors.

Remember to daisy-chain all of those connections together to save wire and keep from cluttering up your engine bay.  I tried to hide most of mine underneath intercooler piping and the like, but if you bought your cables in some spiffy colors, you can also use this to dress up your engine bay.

This is the driver’s side of my engine block.  One of those connections runs to the chassis ground (and from there to the negative battery terminal); the other runs to the alternator.  Note that both connections are on the same bolt, with one ring stacked on top of the other.

If the ground point you’re using is painted or corroded, use a little sand paper or wire wool to clean the area where the ring terminal will be contacting the metal.  And be careful when attaching the ground to the alternator.  If you connect a ground wire to a positive terminal, you will start a fire.  Consult a repair manual if you aren’t sure.

Depending on the layout of your engine bay, some of those connections may be redundant.  For instance, in my vehicle, the computer’s ground is the same point where the negative battery terminal connects to the chassis. If your car has a ridiculously powerful sound system, you may want to increase the size of the cables connecting the battery to the chassis and the alternator to the battery to 0-gauge.  That will make your audio amplifiers more efficient.

The final grounding connections for my car ended up like this:

Negative Battery Terminal > Chassis Ground > Engine Block > Alternator > MSD Ignition Box > Sensor Reference Ground > Firewall

I was actually surprised how much of a difference installing a grounding kit made on my vehicle.  (Keep in mind, however, my car’s electrical system is almost 20 years old.)  The vehicle started quicker because the starter got more power, idled better and had quicker throttle response because the sensors had a less-noisy signal, and had a bit more top-end power since my ignition systems were getting more juice.

So in summary, installing a ground kit can improve your vehicle’s electrical system, especially if the vehicle has old ground wires.  And it really isn’t difficult (or expensive) to do at all!

In my next installment, I’ll give you some tips for tracking down electrical gremlins.


1 comment

  1. Very good read. I would just add a word of caution when tieing Electrical Ground to Signal Ground especially in newer vehicles with more onboard electronics. The Electrical Ground provides the voltage differential to insure things like Spark Plugs work well. However, spark plugs (and wires) also generate lots of signal noise that electronics do not fair well with.

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