Missing ground wire for intake manifold

[dimitrisprophet]

'83 720

 

Just installed a 32/36 Weber (Love it already) and in the process I noticed that I am missing the ground wire for the intake manifold. Looking at pictures I took before the install, I found that it wasn't even attatched in the first place!

 

Before the install, my temp and gas guages didn't work. 

 

After the install, the guages are somehow working? But also the turn signals don't work now??

 

Not sure if this has anything to do with the intake manifold ground. Either way, does anyone has a diagram for the ground wiring? I tried feeling around but couldn't find a loose wire so I'm hoping I can follow a wire to it

[datzenmike]

The battery negative cable should be bolted to the intake near the thermostat. Where is it now????? if anywhere on the block or head it's fine that way.

[DIY 1985]

I found a ground cable on the alternator to the battery, when I bought it.  I added one from the starter to the battery negative, trying to solve what I think is a intermittent starter grinding (bendix?) issue.  There is a smaller black one that was attached to the intake, with a factory-looking ring terminal and two-color wire.  Same thing between the firewall and the driver corner of the valve cover (that can't be right, as there are little non-metal bushings on the valve cover, but who knows).  Then there was a similar, factory looking, ring terminal on the heat shield of the exhaust manifold (Z24 with exhaust O2 sensor).  Since I am running an A/F ratio readout gauge, so I repaired that wire.  That didn't last long.  So, I bent some 16 gauge solid galvanized steel wire into a loop on one end, and ran it for a few inches (to get rid of some of the heat) to a bare crimp connector and regular wire to the firewall.

 

On other truck's factory set-up, there is a thick cable between the head and the battery, and a cable between the starter and the frame.

 

The aftermarket connectors on the turn signals aren't exactly weatherproof, so I might have just used bare connectors and heat shrink, with some electrical tape as harness wrap, I forget.

 

Do the turn signals glow, at all, and not blink?

 

 

Edited January 29, 2022 by DIY 1985

[datzenmike]

Well the large positive battery cable goes to the starter but to complete the circuit there should be an equal size negative cable from the block (or head or transmission as they are bolted together) as a return. The current load is the same in all parts of a circuit so the two cables should be of equal gauge or thickness. The starter draws hundreds of amps so the larger the cables the better.

 

I converted my top battery post to side terminal and found these cables from a GM van. The massive negative was a bit long so rather than shortening it I used one of the starter bolts.

 

Replacement battery cables rarely have a dedicated body ground so if they have been replaced you need some ground wire from the transmission/engine block or head to the sheet metal so electrical components on the body have a good ground return. These components add up so don't be shy of using a 12 or 10 gauge wire for the body ground.

 

Later EFI vehicles have lots of separate ground returns specially the exhaust manifolds for the very sensitive O₂ sensor.