Fuel gauge issue..what could be the cause?
 

68 camaro, turned the car on the other day and the fuel gauge just pegged at what would be 3:00 on a round gauge. Way past full. It has worked fine until now. Stock 68 camaro gauge (original no tach). I assume it's a sending wire problem. Is the signal a negative or positive lead? Where are the problem areas to look for a short?

Thanks in advance for the help.

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funny that you say that cause mine did the same thing last week

check your wire for nicks that would cause it to go to ground on the body.most guages read ohms to ground

sender wire
 

Sounds like the driver coil is seeing all 12v; this could be due to an open in the sender wire. the 'signal' wire is a 0-90 ohm resistance that the sender creates, which changes the magnetic field that drives the needle (by virtue of changing the amount of voltage at the gauge coil). Sorry to dork out on ya... :(

what side of the car does the sender wire run?

90% sure that means you have an open. You can easily check the sender with an ohm meter at the tank before you tear apart the car. You should see between 0-90 ohms depending on how much gas you have in the car. If that checks out you know it's a connection, broken wire, or gauge issue.

fuel gauge
 

It runs down the driver's side...it's the tan wire that protrudes through the trunk pan next to the fuel pipe (to the left looking down). The brown wire is the ground, which needs to be good, or your sender won't do a damn thing.

How are your rear lights? The fuel sender gets it's ground from the same circuit...if they aresketchy, your fuel gauge will follow suit.

great info. thank you all. will check it out on wednesday. will post an update.

Actually the brown wire is power and you have a seperate ground that is near one of your tail light housing.

update
 

the brown wire IS '+'.

I disconnected the sender plug, connected 12v to a short light and touched the wire that is the sender wire going to the gauge and receive a complete circuit. therefore, the wire is obviously grounded somewhere right? or am i seeing this wrong. could the gauge be showing a ground? the wire from the actual sender is showing 30'ish ohms so i assume the sender is OK.

help

I would say so. Unhook the gauge as well to see if it goes back below empty. Places to look would be under your seal plates, sharp eges of the dash, and around the wheel tub in the trunk.

oooooooooops
 

Yep, sorry- my bad..brown = 12v to the running lamps. When you say you got a complete circuit, are you saying that you're seeing the light come on in your test light?

An easy way to test this is to get a 50 ohm resistor (1w) & jumper the Tan wire-through the resistor-the other end of the resistor to ground. If your wires are good up to that point, you should see about a half tank on your gauge (with the key on, of course).

My apologies for the confusion.

update
 

With the key on and the plug at the rear unplugged to the sender the gauge reads way past full. ground the connection and the gauge falls to empty. so i assume the gauge is good and there are no "shorts in the sender wire. therefore, i have a bad sender or a loose wire at the top of the tank right?

thanks for the help, will drop the tank this weekend

Check the ground near the front of the tank near the rearend. A bad ground there will cause your problem. If you need to replace the sender, I STRONGLY recommend the pricey GM sender ($200) over the cheap import ($59). I see at least 1/2 of the cheap ones fail. Always test your new sender with an ohm meter (your old one too) by hooking up your meter & checking that it reads zero @ empty and 90 at full.

I know the GM unit is expensive, but it's worth it!! I swear the aftermarket senders are allergic to gas..:mad:

Also make sure your float is still adjusted properly sometimes if you have an aftermarket one they can come loose but it does sound like you have a bad wire somewhere if it does still still read a voltage but on the off cahnce your float is jacked up you might want to check it out. just my .02