Ground wires

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jefferson
Need some help. When I got my 71 demon the previous owner had pulled and rebuilt the motor and painted the engine bay. Al of the wiring was removed in the process. I bought a wiring diagram and got it all back together but it does not show how many and where the ground straps go. (engine to frame. Alternator etc.) Can anyone enlighten me?
 
Typically there will be a ground from battery negative to core support, one from battery negative to front of driver side head and a strap from rear of passenger side head to firewall.
 
Battery negative post to block.

Head to fire wall.

Headlight sockets to front sheet metal via black wire.

All ignition devices such as voltage regulator, electronic spark control, and alternator cases have to be electrically the same as negative battery post with no voltage drop. If there is some voltage drop between these devices run a ground loop of #12 wire with eyes connected to one mounting screw of each device, and back to negative battery post. These four steps will assure proper grounding for you’re a body.

All connections have to be shinny clean free of paint, and rust, and I would put a little dab of dielectric grease under each connection to keep out corrosion.

If after correcting all major ground paths, engine still does not start, than there is a problem with one or more of the components including coil, ESC, and wiring connecting all the ignition components. You have to print out a wire diagram for your car, and systematically trace and test each wire until the problem is detected.

Often the best place to start looking is a section that was disturbed during the engine work, or a spot that may have been pinched.

Also the dreaded bulkhead connector and fusible link are likely suspects, disconnect each section of bulkhead connector, clean the brass spade connectors, dab with dielectric grease, and snap back together making sure that each individual spade fully mates.

Oh did the rotor button get put back on???? And, check that distributor is not 180 degrees out.
 
All good advice. Look at your passenger side head where the alternator mounts. Those same bolt holes are on the rear of the driver side head. Buy a 1 ft long "starter cable" IE "ring terminal to ring terminal" no4 cable. Bolt it to the rear of the head with a short bolt, and the other end to one of the master cylinder studs.

And as wjajr said, the bulkhead connectors are becoming a huge problem
 
Some grounds are thru the case of a component, which can be a problem. As mentioned, don't rely on a sheet metal screw to ground the electronic ignition module or the voltage regulator. The factory did that, but it causes many problems 40 yrs later. I once had a "bad" alternator in my 69 Dart, but a rebuilt one didn't fix it. Ran a jumper from the alternator case to BATT- and it started working, so I removed it and sanded the case and bracket contacts. Worked fine after that and I returned the rebuilt one, since I swapped it right there in the parking lot.
 
Thanks for all the great information guys. I only had a negative battery cable hooked up so far. Maybe that is why the coil spark is so weak?
 
Very possible. If there is no ground from the battery or block to the body, there is not much to "hook the two" together. Motor mounts are rubber, so only "accidental" stuff grounds the block. If you run an automatic, with original all metal cooler lines, those are probably forming "the best" ground with no proper ground cable(s). Otherwise, poor connections in clutch or shift linkage, REALLY poor connections in the throttle cable, etc, is really the only connections
 
So true:
If there is no ground from the battery or block to the body, there is not much to "hook the two" together. Motor mounts are rubber, so only "accidental" stuff grounds the block. If you run an automatic, with original all metal cooler lines, those are probably forming "the best" ground with no proper ground cable(s). Otherwise, poor connections in clutch or shift linkage, REALLY poor connections in the throttle cable, etc, is really the only connections

Whenever there is a high resistance path to negative battery terminal something along that path is going to get smoking hot as soon as the starter is engaged be it a loose connection, oil cooler line, several smaller gage wires not meant to carry a big amp load, linkage between clutch and dash or carburetor & fire wall. This is why such a heavy gage conductor is used between block & negative battery terminal.
 
Installed a double eyed battery cable from the back of the head to the master cylinder bolt and sanded the metal under all of the components mounted to the firewall. Here goes.....
 
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