PLEASE HELP!!! I can't get this #!@&!! fuel gauge to work...

[barsteel]

Hello!

Last week I posted about trouble I was having with the factory gauges on my '68 Z8.  Right now, it's the fuel gauge that's really got me stumped.   Here's the situation as it sits now.   One warning...I am duplicating the connections that I saw when I first pulled the gauge pod.  It appears as if someone may have had the pod out before, so I cannot speak to what someone may or may not have done before I got the car.

I read through the gauge tech threads, and I ran all of the tests.  There doesn't appear to be anything wrong with the wiring.

Gauge is new.  Rick's Camaros sent me 2 by mistake, so I have a spare to test my results.

I have a measured 11.5v coming from the doubled up pink wire that goes into the 2 prong factory plug.  The plug appears to be intact.

The sending unit measured about 88 ohms with the tank full.  To make sure it wasn't stuck, I drained about 6 gallons from the tank, and the resistance dropped to about 30 ohms, so I know that the sending unit it working.

With the factory plug plugged onto the gauge, and the gauge mounted, I have the same voltage current flowing into the sending unit - I checked at the plug that's behind the trunk lock mount, although the test light appears to be very dim.  So, I have current flowing through the circuit as it should be

Per the directions, the gauge is an internally resisted gauge, so I do NOT need the factory shunt resistor.  The gauge came with a phenolic plate that replaces the shunt resistor.

I mounted the gauge with the phenolic plate on the outside of the gauge pod, between the two mounting lugs, just as the original shunt resistor had been.  The copper colored middle bottom lug was simply fastened down with the factory nut and lock washer.  The nut/washer are in contact with the gauge's mounting plate.

There appears to be a threaded hole in the back of the gauge, top center (see pic).  There was nothing in that hole when I removed the gauge that was in the pod, although there's a matching hole in the mounting plate.

No matter what I do, the gauge pegs full.

Pulled the gauge from the pod and made all of the connections with alligator clips...power from the factory plug to the left terminal (looking at the back of the gauge), a lead from the right lug to back to the other terminal in the factory plug.

If I turn on the key with those two connections, I get nothing.  If I ground the bottom middle copper colored terminal, the gauge pegs full.

If I ground the gauge housing with the 2 connections above, I get nothing.

If I feed power to the left lug, leave the right lug unconnected, and ground the bottom middle copper lug, the gauge pegs full.

I'm fairly certain that I'm grounding something I'm not supposed to be grounding, or I'm not connecting something correctly.

I have the factory manual, but it doesn't give a detailed picture of the gauge connections.

Please help me get this sorted out.  I've put several hours into this and I'm at a dead end.

Thanks...

Chris
Monroe, CT

[barsteel]

Here's the gauge as I "think" it should be set up.

You can see that someone enlarged the holes in the mounting plate.  I have no idea why.  There's also the hole in the top of the plate that matches with the center top hole in the gauge.  There was no screw in that hole.  Should there be something there?

Thanks...

Chris

[barsteel]

Further comments - measured the resistance from the hot terminal in the factory plug to the sender terminal, and I got about 30 ohms resistance.  Re-checked the resistance of the sender at the plug behind the lock mount in the trunk, and got virtually the same reading, about 30 ohms.  So...I'm getting current into the gauge at the correct voltage, I know that there's no break in continuity in the sender wire into the trunk, and that the sending unit is working properly.  I also cleaned the sending unit ground at the pass side fuel tank strap holder, and added a temporary ground to the gas tank just in case.

Still, the gauge pegs full, although it's slow to react.

Also, the gauge does NOT return to empty when you turn off the power.

Chris

[69pace]

Chris your situation indicates you have a ground issue. If you ground the leg that the sender signal from the tank is on you should get past empty if the gauge ground lead is working.

I don't have my resources here at work, and you don't have the Low Fuel Warning - module hooked up so in simple terms: Pink is power and is on the right terminal, Black is ground and is on the bottom, and brown or tan the sender lead and is on the left.  Looks as if you have the leads backwards as well. Here is a photo from a post over at Team Camaro. Let me know if you need any local help.

[69pace]

And to answer you last comment -  the gauge will never return to empty at shutdown on its own, they weren't designed to do so, however gravity will move the pointer down a bit once it is on the shy side of half.

Brian

[barsteel]

Pace - THANK YOU!!!

I corrected the connector mounting, switched the connections, and ran a ground wire to the bottom lug...lo and behold, the gauge slowly climbed to 1/4 and stayed there.  I added the fuel that I'd drained, and it rose to 3/4, so the gauge appears to be working correctly.

Chris

[barsteel]

Brian -

One additional question - I was under the impression that a car with the gauge package should have a low fuel light as you mentioned.  Mine does not appear to have one, although I do know that the gauge layout is different on a 68 vs a 69.  The only unconnected wire under the console is a single yellow wire, and I have no idea what it's for...any idea?

Thanks again...

Chris

[69pace]

1969's all have the light on the instrumentation pod on the left, 67 and 68 the OIL light becomes the Fuel light when the car has console gauges. If the conversion was done including the Tachometer, then the printed circuit should reprogram the light. Then you buy the new dash indicator lens that has FUEL printed in that location http://www.camarocentral.com/1967_1968_Low_Fuel_and_Brake_Red_Indicator_Lens_p/das-208.htm

As to the module, it is mounted in series with the gauge and when the set-point is reached in Ohm's it triggers. The actual Low Fuel Warning Module grounds out in 68 and 69 to light the FUEL indicator via the yellow wire, so they are interchangeable. 67 actually sent power over the yellow when the set-point was reached.
http://www.mattsclassicbowties.com/contents/en-us/p10651.html
The OEM modules had a set-point that triggered between 1/4 and 1/8 of a tank. In that age when there was at least one station on every street corner that was warning enough with a 20 gallon tank and a thirsty engine. Now it perilous at best. You can now buy a variable module from M & H Electric that allows you to set the set-point where the light would light, say the more realistic 3/8th of a tank.
http://www.wiringharness.com/

So it sounds like all you need is a module, hook it up, connect its yellow to your yellow and you are in business.

[barsteel]

Brian -

Thank you for the response.  My gauges don't have any module on them, so it was probably removed at some point for whatever reason.  I still have the yellow wire, so I will test the light by grounding it.

Does anyone make a replacement module?  I'm not concerned about the trip point, so an original type repro will work for me.

Thanks...

Chris

[69pace]

Yes there are OEM replacements and the variable unit. I posted links to variable and one to Matt's Classic Bowties, but the OEM module is available everywhere and most are made by Lectric Limited or Classic Headquarters. The OEM's run in the 50-60 buck range most of the time. You would wire the red tot he pink connection, green to the sender lug, black to the ground and the yellow to the connecter you have hanging. About a 15 minute install, 30 including swapping the lens.

[HawkX66]

Another view like 69Pace posted..., but from my 69. Edit: That's what I get for posting in a thread I read earlier... Already fixed. Glad to see it.