Talk to me about grounds

So, I've never built a car before.  Maintenance and repair of pretty much any kind, sure.  Rebuild an engine, sure. 

The Chevy II started from a nasty old mess and now has a new engine and transmission and a bunch of new panels and a pretty paint job and a Painless ( HA! ) wiring harness.  I'm actually getting close to a point where I'll need to be testing circuits.  Before I do that, I want to make sure I have all the grounds I need.  I know I need a big wire from the negative terminal on the battery to the engine, engine to body, neg. term to body.  I read about people wanting to ground hoods and trunks to dissipate "static".   Is this necessary?  Desirable?  Do I need to ground the doors??

Not sure this is a great pic of the car, but it's a great pic of a great dog! 

You basically can't have too many ground connections from the engine to the car.  As an example, in addition to the negative cable that goes from the battery to the engine block in my old '61 Pontiac, it also came from the factory with four ground straps on the engine: one at the front of each cylinder head goes to the frame, and one at the rear of each cylinder head goes to the firewall.  It also has ground straps from the frame to the radiator support, since the radiator support is on rubber bushings.  Your car is unibody, so you don't have to worry about frame to body connections.

You shouldn't need ground connections to the hood or trunk lid since they don't have any electrical devices in them, and they're grounded through the hinges anyway.  If there are electric windows or speakers in the doors they most likely have their own ground wires, so the doors shouldn't need any additional grounding either.

It goes without saying to make sure your taillight and headlight circuits have ground connections that are made to clean metal.  Same with any connections under the dash to the instrument cluster or any other electrical items.  More often than not, any static or intermittent electrical issues in a car can be traced to poor ground connections.

A good ground on the hood helps reduce electrical noise and makes the radio work better.

RonPNW said:

A good ground on the hood helps reduce electrical noise and makes the radio work better.

 

Thanks.  I had read that elsewhere.  My wife asked me to go to the trouble of installing a nice radio and a pair of decent speakers.  I'm not sure we'll be able to hear it over the engine noise, but I suppose I should take advantage of grounding the hood.  By the same reasoning, ground the trunk also?

I wouldn't bother grounding the trunk lid.  Engine lid is a metal antenna on top of the ignition, it's got a lot more happening nearby.

1988RedT2 said:

Not sure this is a great pic of the car, but it's a great pic of a great dog! 

Doggo sez you don't want none of this!

I will leave this here.

So here is my unabridged version of automotive electrical grounds:

Battery to Engine Block = 1/0

Engine Block to Frame = 1/0

Frame to Battery = 1/0

Frame to Firewall = 4ga woven strap with post that extends to both inside and outside of firewall.

Firewall to Dashboard = 4ga woven strap

Frame to Rear Body Ground = 4ga woven strap

These suggestions are for body on frame vehicles, I suggest unibody vehicles utilize a large gauge distribution block to unify all ground planes, and I use them in all vehicles because I found that it's too easy to miss a failing ground. 

The hood should be adequately grounded through the hinges and the latch, but I suppose an additional connection can't hurt.  I assume you're not running solid core spark plug wires or non-resistor plugs so there shouldn't be any ignition noise to speak of.