vzfox

Ok....I am looking for some confirmation on my findings.....my fuel gauge isnt functioning properly. With a full tank of gas, the gauge will only rise to 1/4.

I ohmed out the head unit of the dash for the fuel gauge....using my odometer, I am sure it is getting real close to empty. The ohms read 75 ohms. (20 miles ago it read 100 ohms) I am almost sure that if I put a full tank in it the ohm reading will be above 200.

Can anyone confirm or deny that my sender reads high ohms at a full tank and low ohms at empty? I have tried doing many searches for fuel gauges and what might work in my Z28. I have found that some gauges work on a 0-90 ohm ratio, while others work on a 33-240 ohm ratio. I would think that my sender is the 33/240 from what my readings are giving me, but I also read that "most" GM vehicles work on the 0-90 ohms ratio. I just need someone with a Camaro like mine to confirm my findings/readings so I can determine that my sender is actually good and that the gauge itself is bad. If you need to know what terminals I am ohming on the dash head unit.....there are three terminals, I am ohming the bottom two with the key on.

jv9999

iTrader: (1)

Yes. If the connection is shorted, it reads empty. If open, it reads over full. The service manual says it should read between 1/4 and 1/2 at 90ohms.

vzfox

In other words, the readings I am getting are true and accurate, correct? And my sending unit is good, but the gauge itself is bad, correct? Does this mean I still have about a 1/4 tank of fuel at 75 ohms? Where can I get a copy of this service manual and the page(s) you are looking at?

thanx, this helps and saves me alot of time and money.

jv9999

iTrader: (1)

It does seem that way. Both that the sender is good and that you have a 1/4 tank or so. Does it go to full if you disconnect the sender? If it doesn't, either the gauge itself is bad or it's not getting the right voltage. Are the nuts tight on the back? Are all the other gauges OK?

vzfox

When testing voltage at the dash unit connections, I get 12 volts. I have not however disconnected the sender to see if the gauge itself will reach full. The only other gauge that does not work is the volt gauge, it has two terminals on the dash head unit and when testing with a multimeter, it reads 12 volts. So I am almost sure the volt gauge is bad.

jv9999

iTrader: (1)

Might be related. In 30 years I've never seen a bad gauge. Lots of bad connections and bad senders. That gauge might need a ground too. Are there two or three nuts on the back? I have the wiring diagram book around here somewhere...

vzfox

On the fuel gauge itself, there are three terminal leads. Two of them have "nuts" on them and are copper. The other one has no "nut" and looks to be plain steel. The same goes for the volt gauge, but the dash head unit only has two terminals for the volt gauge to plug into, so the "steel" lead on the volt gauge itself is not used. The dash head unit for the fuel gauge has three input terminals.

I can see where your coming from and going with the "ground" issue, but if there were no ground for the fuel gauge, it wouldnt move at all.

Let me see if I can explain in detail what the fuel gauge is doing.....with a full tank of gas, the gauge will read 1/4. But, as the fuel level drops, so does the gauge needle. Since it is only going up to 1/4, the needle will move real slowly towards the E. Once it reaches the E, the tank is actually empty. Picture the 1/4 mark on the gauge as a full tank, so the needle only has to move maybe half an inch to reach empty. Keep in mind the ohm readings I am getting from the dash head unit, which seem to be accurate from the service manual you are looking at and in order to get a 12 volt reading from the dash head unit, a ground "has" to exist. I hope that wasnt confusing, but that is what the fuel gauge is exactly doing.

Jproz1167

iTrader: (3)

hey if u need a 86 z-28 cluster let me know I will give you a good deal on one

vzfox

Thanx, but I just bought a cluster off of Ebay yesterday ($35). After the discussion(s) I have had with jv9999, I am leaning towards bad gauges.

KYLE87

iTrader: (5)

IVe had trouble with my gauge for some time, I switched to a different one it was a little better but not much, well I jsut had to have a gas tank leak fixed so had the sender and intank pump replaced as well, now the gauge doesnt go over the full mark but right on the line but when i brake the gauge is everywhere

DukeofHurl

The fuel guage on my car is always at past full. So does that mean the sender is no good?

BTW I tried replacing the fuel guage before and it did the same so I switched back to the original.

klause83z28

Yes the sender is bad. if it always reads full, there is an open wire at the sender. Mine does the same thing, I have a working sender to put in it but don't wanna do it just yet.

vzfox

I bought a gauge cluster from ebay about a week ago. I just took the fuel and volt gauges out of the cluster I bought and put them in my current cluster in my car. The volt gauge now reads as it should and the fuel gauge also works like it should. I guess the problem I was having was the gauges after all. This will be a first for me, having actually gauges go bad.

H8U666....as far as your fuel gauge always reading above full and never changing or going low; sounds to me like the arm on the sending unit is either stuck or hung up on something in the tank, or it could be that the gauge is bad. You can test your cluster head unit by reading thru this thread and doing what I had done and that will tell you where your problem is.

camaropunk....cant be sure what your problem might be, but almost sure it is a wiring issue.

DukeofHurl

Well I replaced the guage b4 and it had no effect. And when I replaced my fuel pump the arm moved freely...so I guess it has to be the sender or in the cluster somewhere...

KYLE87

iTrader: (5)

so your gauge goes down when its supposed too nd not at random times? Does it stay steady when braking and accelerating? someone said thirdgens just do this, but it seems a bit much to me. Im looking to find a new gauge from someone who knwos it works and im gonna try swapping that

Hunnicuttz

iTrader: (1)

My gas guage is doing the same thing that vzfox guage did but mine is empty at 3/4 and it goes way past the F mark when full. From reading this forum it seems that I also have a bad guage because everything else works fine and the needle moves on the gas guage but just never goes below 3/4 when empty.

Does anyone have a gas guage for sale for a 1992 Formula?