[dataway]

I was wondering if you any of you have checked resistance between the battery negative post and various ground locations. I've got new, good connections ... batt. to engine of course, head to firewall, frame to inner fender on the pass. side.

I get 0 ohms to engine, 0 to hood hinge, 0.6 - 1.1 to various grounded components on the firewall (like relay covers).

I'm going to install another strap from the negative terminal on the head, to the adjacent inner fender .. which will be the only non-stock ground strap. I'm not real confident with the single pass. head to firewall strap that is used on 68 A bodies.

[Indy1k]

I just did this too because I did not have zero ohms between engine and chassis. O'Reiley's has a 15 inch ground strap I ran from chassis where inner fender well grounds up to the passenger front head. All is at ground now! No chance of wire fire.

[Stuart]

I don't know about other years or models, but in 1961 they used four ground straps on the engine (one from the front of each head to the frame, and one from the rear of each head to the firewall) along with a couple more straps that go from the radiator support to the frame. You can't have too many ground connections. The straps are fastened with toothed washers as well to make sure there's a good connection.

[dataway]

I hated to do it ... being that it's not stock, but I added an extra one from the drivers side head to frame, and one from the negative battery terminal to the fender ... tried to tuck that one out of sight. Hard to believe the 68 A bodies had a single ground from engine to frame.
But ... they sold a LOT of shifter cables because of that, people forgetting to reinstall it after and engine was out ... first time you turn on the headlights it grounds through the cable and melts the liner ... don't ask me how I know ... twice

[OG68]

Third time was the charm huh?

[Geoff]

The standard DVM is not very accurate at reading low ohms. I have a special ' low ohms' meter for that purpose.

[Scarebird]

Originally Posted by dataway

...they sold a LOT of shifter cables because of that, people forgetting to reinstall it after and engine was out ...

Had that happen with my first car, a 69 Cutlass.

I ground the hell out of the car now, especially with trunk mounted battery and ECM.

[dataway]

Originally Posted by OG68

Third time was the charm huh?

The third time I showed up at the Pontiac parts counter the older gentleman working there asked ... have you had the engine out lately? I said yes, he asked if I put the ground strap back on ... I said ... what ground strap? Then he explained the situation. That was about 1978.

[Bill Hanlon]

Originally Posted by Geoff

The standard DVM is not very accurate at reading low ohms. I have a special ' low ohms' meter for that purpose.

Another way to look for a high resistance ground path is to use your DVM on a DC low voltage scale. Turn on all lights, radio, etc and have the engine running. Put one probe of the DVM on the negative post (not the negative cable) of the battery, then use the other probe at various places that SHOULD be at ground. Any reading more than a tenth of a volt or so is telling you that the ground connection isn't all it should be.

You can also use this method for testing for poor connections in the starter circuit. Leave the probe connected to the battery negative post. Hold the other probe against the starter case at a clean, bare of paint, spot. Remove the coil wire then have a helper turn the key to the start position. Voltage reading should be less than 1/2 volt. If not, the engine is not properly grounded.

Now move the battery probe to the positive post. Move the other probe to the large lug on the starter solenoid nearest the starter motor. Have the helper turn the key to start. Voltage should be less than 1/2 volt again. If not, move the solenoid probe to the other large lug on the solenoid. Hit the key again. If voltage is now less than 1/2 volt, the solenoid is defective. If you are still reading move than 1/2 volt keep moving the probe back towards the battery until you get a lower than 1/2 volt reading when spinning the starter to indicate where4 the high resistance starts.

[Shiny]

Originally Posted by Bill Hanlon

Another way to look for a high resistance ground path is to use your DVM on a DC low voltage scale. Turn on all lights, radio, etc and have the engine running. Put one probe of the DVM on the negative post (not the negative cable) of the battery, then use the other probe at various places that SHOULD be at ground. Any reading more than a tenth of a volt or so is telling you that the ground connection isn't all it should be.

You can also use this method for testing for poor connections in the starter circuit. Leave the probe connected to the battery negative post. Hold the other probe against the starter case at a clean, bare of paint, spot. Remove the coil wire then have a helper turn the key to the start position. Voltage reading should be less than 1/2 volt. If not, the engine is not properly grounded.

Now move the battery probe to the positive post. Move the other probe to the large lug on the starter solenoid nearest the starter motor. Have the helper turn the key to start. Voltage should be less than 1/2 volt again. If not, move the solenoid probe to the other large lug on the solenoid. Hit the key again. If voltage is now less than 1/2 volt, the solenoid is defective. If you are still reading move than 1/2 volt keep moving the probe back towards the battery until you get a lower than 1/2 volt reading when spinning the starter to indicate where4 the high resistance starts.

Yes, this is good advice. Voltage drop is a much more reliable indicator than resistance for checking grounds. You just need to be sure the loads are there as you describe.

Accurate resistance readings anywhere close to zero are typically done with 4-point measurements and handheld volt-ohmeters aren't usually set up for that. A budget voltmeter can read millivolts with good accuracy... but half an ohm... not so much! And even a good solid mechanical contact will have measurable resistance... like 0.1 to 0.2 ohms... so zero is not even a realistic indicator.

Your method also checks out the conductors, which is a big bonus. You can have great contacts on a wimpy conductor that drops too much voltage.

[dataway]

Going to apply this knowledge in the spring shakedown before deeming the GTO roadworthy.