88PontiacT/A

Anyone seen this before? Where do I start in order to find what is causing this problem? All suggestions are appreciated.Sorry if this not posted in the correct forum...

Mad_IROC-Z

If you unplugged your signal wire you would get a full tank. Its the resistance to a ground which makes it go up. Not being plugged in or the ground wire broke or not a good ground would all make it rise to or past full.

88PontiacT/A

So, if the wire(s) that connect to the back of the guage are not getting a good connection, or it/they have come unplugged from the guage, would this cause the same problem? Is there a fuse or a circuit breaker for it or something? I haven't taken anything apart on the car other than the top of the motor in order to replace the fuel injectors. I'm not sure if the fuel guage was messed up before or not.

I bought the car, drove it home, and started working on replacing the things that it needed under the hood in order to get it to run smoothly. It has been sitting since mid october, until I finally had time to get it back together and running yesterday. That is when I noticed the Guage was pegged. Drove to the gas station and it took 12.5 gal to fill it up.... :-/ Thought filling it up would maybe make it start working again I guess?.?.? Still pegged past full after driving 45 miles.
John C.

Mad_IROC-Z

The fuse is for the fuel gauge is the same for all gauges. If they work then its not the fuse. They also share the same ground.
The signal wire for the fuel gauge is a ground. 0ohms empty and 90 ohms full.
If the pink signal wire from the gauge to the sender were taken off or cut there would be no connection to ground and would make infinate resistance. Infinate is closer to 90 ohms than 0 ohms. So the gauge would go to full. 0 ohms would be a perfect ground signal.

I think the fuel pump shares the same ground as the sender so if your fuel pump works I would think that the senders ground is good.

88PontiacT/A

What if the sending unit goes bad? Could that cause this problem, or do you think it would more likely cause the opposite and the guage would stick on E? Is it very much of a pain to get to the back of the guage and access the wire where it is connected on the back? Do you think I can reach up under the dash and get a couple of fingers on it, or will i have to pull the radio or the cluster out to get to it? Thanks for all of the info, BTW.

NINÅ

Mad_IROC-Z

Its a bigger pain getting to the sending unit. You would have to pull the cluster to get to the wires. The pugs that go into the cluster are clipped into the dash panel and will stay with it when the cluster is removed.

You can check continuity of the gauge wire. From the cluster wires and there is a plug on the car above the rear end in the center of the body.

88PontiacT/A

Thanks for the info. So, the plug above the rear diff contains the sender wire along with the wires for the pump? Do you know what color that sender wire would be? If I un-plug this connector, and substitute a potentiometer (in place of the sender) at the end of the harness which leads to the front (guage) and perform the test described above, Shouldn't i get the same result as long as the harness has no problems from the rear axle forward? If so, and the test were to show the Guage working properly, this would be isolating the problem to behind the rear axle, right?
Unfortunately, I work every day this week from before daylight 'til after dark.... Guess I will try to look at it as soon as I can. Plus, I have to work on the car outside and the low temps are supposed to be in the low 20s (not to mention high winds) for the rest of the week w/snow and freezing rain thurs night and friday. Not really good weather for working on cars outdoors. Supposed to warm up to ~60 this w/e tho.... maybe I'll have time to look at it then.

NINÅ

zenish

mines a camaro so it may be different.my gas guage used to get physically stuck at the top.id pull the cover and free it.later it would do it again.i had to replace the guage.now my temp guage does the same thing.does your gas guage move when you turn off the car?

88PontiacT/A

Nope. Stuck pegged past full...When I parked the car a few months ago, I believe the guage was reading correctly. Honestly I can't remember. I bought the car, drove it home (don't remember it being full of gas when I got it) and took the motor apart to replace the smog pump and the injectors. That was last october. Finally got it back together and running last sunday, looked at the guage and it was pegged..... wtf? Drove it to the gas station and put 12+ gals in it. :-/ I've driven it ~45-50 miles since then and the guage is still in the same spot-with the ignition on OR off.

NINA, (and everyone else too) thanks for the info. I'll dig around and see if I have a 100 ohm pot somewhere and if not I'll make a trip to radio shack saturday and pick one up so I can test this thing...I'll let y'all know what I find out.

88PontiacT/A

Went to radio shack to get a 100 ohm pot today. Of course, they had nothing anywhere close.... figures. BTW, how does the fuel guage get its 12V. I'm guessing that it comes from the 12V source to the guage, then from the guage out to the sender, then from the sender to ground? is that right?
John C.

NINÅ

88PontiacT/A

LOL! I just came back to ask this question, and the answer was already waiting for me. Thanks for that. I'll go check them out...
John C.

88PontiacT/A

Would this one be sufficient? Looks like the only one they have....
http://www.parts-express.com/pe/show...number=023-604

NINÅ

88PontiacT/A

DAYUM! Almost 14 bucks to ship something that's the size of a bottle cap, weighs almost nothing and costs less than 4 bucks?!?!?! What a ripoff!

NINÅ

82tarecaro

iTrader: (4)

Did you ever fix this? I started my TTA for the first time this season and the gauge is pegged at full. If I remember right, when I parked it, it was almost empty. It looks like I may be installing a fuel pump and hotwire kit if the sender is bad. It is just strange that it is stuck on full when the tank was empty and the float was down.

88PontiacT/A

No, It hasn't made it to the top of my 'to-do' list yet. My son drives the car every day, and I've just been having him keep track of how far he drives, and filling up the tank ~ every 160-180 miles 'til we get a chance to mess with it. Plus, I'm Too cheap to pay $15 shipping for a $3 part (potentiometer) that weighs less than one ounce, and noone locally sells anything like it- not even Radio Shack.
John C.

toy4x4

Go to radio shack buy a Two 100 ohms resisters for $2 they come in a pack of 5 resisters. Use one 100 ohm resiter to see if guage reads full. Use two 100 ohm resisters in parallel = 50 ohms and guage should read half tank. Then just ground the lead and tank should read empty. Cheaper and just as easy as pot

mrrman

marked

88PontiacT/A

Yeah I thought about using resistors (i guess wattage doesn't need to be too high for this, right?) BUT....My son calls me about 3 days ago and says' "Hey, I just looked at this fuel guage in my car, and it is on 3/4 tank mark!" "It also moves up and down some whenever I slow down / speed up / or turn a corner!" So, i figured maybe it's fixed itself.....Then he comes home that night and says " The guage stopped working again." Then, next day... "Hey, It's working again!" So I guess it's either a bad connection somewhere, or the sender was gummed up from the car sitting a few years before we bought it and now the gunk is starting to dissolve away?... I don't know. :-/ guess we'll let it ride a while longer and see what happens next.

J. Campbell