Hello!
After long last, I got my '68 Z28 on the hoist and checked everything out before the first maiden (more than 10 minutes) voyage. Topped off the fluids, new rear brakes, lubed everything, oil chg w/ZDDP, new plugs (old ones were fouled). Started up and ran great, but I still have some issues with the gauges.
Ammeter and fuel gauge didn't work, temp gauge only went to a quarter hot, so I had no idea if it was accurate or not.
I did some reading on the wiring, pulled the gauge package from the console and found that the internal (from outside the gauge pod to the fuel gauge) ground wire had been melted, and that the contacts for the ammeter and the temp gauge were badly corroded. I pulled the gauges, replaced the ground wire, and cleaned all the contacts. When I put everything back together and started the car up, here's what happened:
The ammeter now works (it shows a slight charge after starting the car, then goes to center, and will flicker slightly if I turn on any accessory) - victory.
The temp gauge now pegs to full hot.
The fuel gauge still does not work, although it appeared to move slightly (1/16") when I started the car, but it still basically shows empty with a full tank. It now has a good ground (tested), and current flowing into the gauge through the pink wire that feeds into the gauge plug.
1) Temp gauge - how can I test if the gauge itself works?
2) If the gauge works, is the sending unit (driver's side of the head) probably bad?
3) Is there a way I can test the sending unit?
3) Could the shunt be bad? If so, how do I check it?
I'm not a big fan of randomly replacing parts, so I want to isolate exactly what's bad before I start spending $$.
As far as the fuel gauge goes, the previous owner said that he replaced the sending unit, but I haven't dropped the tank to check it out.
1) Can I check if the sending unit is bad without dropping the tank, i.e. check the ohms resistance between the hot wire and the wire to the sender?
2) Any way I can check if the gauge itself is bad?
Last issue -
The tach is WILDLY inaccurate. With 3.73 gears in 4th, it shows that the engine is turning 5800rpms at 70mph. It's not. I don't have another tach on it, but I'd guess that the motor is turning around 3200rpms.
One note - the car originally has 4.56 gears, and the previous owner swapped it to 3.73 gears. My understanding is that the tach is driven by an electrical impulse from the distributor, correct me if I'm wrong.
Any idea why the tach would be so far off?
Thanks in advance...
Chris
