fuel reading problem - Team Camaro Tech
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post #1 of 18 (permalink) Old Feb 28th, 04, 01:35 PM Thread Starter
 
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I have a 1967 camaro, that is reading the incorrect reading on the guage, it is basically 1/4 off on the reading so an empty tank is at 1/4 of a tank instaed of the "E" like it is suppose to be. When I fill the car up to capacity it goes just a little bit past full but stays there a while untill some good driving is done before it moves back towards the "E" direction keep in mind empty will be at the 1/4 tank mark, my guage is not crooked or anthing, and i dont recall this happening to me before winter, I basically threw a cover over it last november just got her going this week feb 26th 2004... i did install another electric fuel pump next to the tank no biggie two wires and 2 bolts it humms good, while doing that i notice a black wire that was coming from the tank, it poped off so i take it to be a ground wire, i figure maybe it wasnt grounded so that would cause the misreading, however keep in mind that the main sending unit wire coming up from the licence plate area when i disconnect it the fuel gage reading goes way past full like half way to the opposite end on the guage, when i connect the wire back and give it juice the gauge reading goes back to what iy feels the tank is at, this is regardless of whether or not the tank is grounded, someyone told me a while back when i replaced the tank that the sending unit only comes with one wire anyway which is the wire that is by the licence plate regardless of whether i ground the tank or not usually it would work any way, i hope im not confusing my words, anyways do i have a sending unit problem where the float isnt accurately sending the proper reading? or does it sound like a guage problem? i think its the sending unit, because like i said if i disconnect the main wire by the licence plate going through the garmet into the tank the guage goes way past full , i take this to be the pre sets to the guage, please help, thanx god bless
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post #2 of 18 (permalink) Old Feb 28th, 04, 02:01 PM
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I had a simuler problem with mine. What you do is unhook the wire going to the sending unit,when you do this the gauge should read way past full.Then take and ground that same wire and the gauge should read empty. If it does then the gauge is good and you need to replace the sending unit.But before replacing the sending unit check and make for sure that the currnt sending unit is grounded good or it will not read correctly.If it is then get a new sender. Good Luck [img]graemlins/thumbsup.gif[/img]

1968 camaro 350,th350,3.55 gear
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post #3 of 18 (permalink) Old Feb 28th, 04, 02:03 PM
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possibly the sending unit float getting stuck around a 1/4 tank? do you know if it's actually empty at that 1/4 tank mark or it just stops there? i don't think there's much of a difference between a 67 and a 69 sending unit, but i could be wrong. i replaced mine last year. with a bad ground, the gauge will flip to way past full(about 3 o' clock) like you were talking about. that kinda baffles me that yours is pretty much working without a ground. maybe it is grounded somehow and it's just not a good ground. which may explain why the gauge isn't working perfectly. i would check your ground wire and see if that changes anything. if it did pop off at the sending unit, you may have to drop the tank to solder a new one on or get a new sending unit. this web site might help you out too if you wanna do some tests. good luck [img]graemlins/thumbsup.gif[/img]
http://members.core.com/~faldrich/fuelgage.htm

69 Camaro - LeMans blue w/ black vinyl top - 350/TH350
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post #4 of 18 (permalink) Old Feb 28th, 04, 03:25 PM Thread Starter
 
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thank you both, yes the car runs out of gas at 1/4 of a tank, i did drop the tank today and connect a ground wire, still no difference,

I just came from doing the grounding test and the guage goes to 3 o'clock past full, i tried the test on my 68 and it does the same thing, neither of them go to empty when grounding the wire so i dont know, is there another to check the guage? or is the float just getting stuck in the tank on the sending unit?
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post #5 of 18 (permalink) Old Feb 28th, 04, 08:12 PM
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did you have the ignition key turned to the on position when you tried to ground the sender wire? its easy to get mixed up when you're doing those tests. it took a pretty good ground for my gauge to read empty. and make sure you're grounding the wire coming from the gauge, not the side running to the sender, i mixed that up too [img]graemlins/clonk.gif[/img] if you can do that test, you should be able to find out whether your gauge and wiring to the sender are good. if it passes and reads empty, then that should narrow it down to a problem with your sender.

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post #6 of 18 (permalink) Old Feb 29th, 04, 02:40 AM Thread Starter
 
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im positive that i disconnected the wire going to the tank going through the rubber piece to the tank , the guage goes to 3' oclock, i used a new wire and connected it to a known good ground where my amp goes, i know its good because the amp wont work if its bad, still the guage doesnt go to empty, yes i had thee car running while doing this test, i even tried it on my 68 camaro, and it does the same thing , goes to 3'oclock , i tried to ground it and it doesnt change, i am going to test it with a voltmeter, im pretty sure its the sending unit and not the guage, why would the guage even work at all? i figure it would just go to 3, oclock or simply not move at all if broke, my frind has a 69 as well, but he's out of town with with wife and kids, maybe the 69 is a little different as far as the guage is concern..` i looked at a manual and it says to test it with another sending unit , without putting it in the tank or anything simply hold it in your hand connect the wires and mover the level whooyah up and down and if the guage moves as you move it from full up position all the way down to the empty position then the sending unit is bad.. i wish i could narrow it down more, its not hard to remove the tank at all, the sending unit itself is the bugger because i dont have the gm tool for it, i guess you have to hit it with a flat nose and a hammer i dont know thanks for the help ..
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post #7 of 18 (permalink) Old Feb 29th, 04, 04:52 AM
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Have you double-checked the grounds and connections at the guage and guage cluster itself yet?

Found these doing a forum search:
https://www.camaros.net/cgi-bin/forum...;f=10;t=002605

https://www.camaros.net/forum/ultimat...=002547#000000

http://members.core.com/~faldrich/fuelgage.htm

https://www.camaros.net/techref/ftecref18.html

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post #8 of 18 (permalink) Old Feb 29th, 04, 06:03 AM
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i did do mine with a flat nose and a hammer. probably not the right way to do it, but it works. just make sure you have another lock ring, i mangled mine pretty good trying to get it off. you may want to try putting a towel or some other padding between the screwdriver and the lock ring too, that could save it. i would bank on it being the sending unit too, it gets a lot of abuse over the years in the tank. they are fairly cheap. i got mine from rick's for 50 bucks, works great.

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post #9 of 18 (permalink) Old Feb 29th, 04, 11:04 AM Thread Starter
 
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i checked it again this time with a longer wire finding a bolt on the frame and the guage goes to empty when the brown wire is disconnected and grounded it goes to 3 'oclock past full when its juust seperated from the sending unit wire, so i am convinced that the wiring all the way to back and the guage is working, somehow the sending unit is bad, i have checked several places is 75.00 to much?
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post #10 of 18 (permalink) Old Feb 29th, 04, 02:08 PM
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Yeah it's the sending unit. NPD (national parts depot) has them for $60.00.You can reach them at 1-800-521-6104.Thats where i got mine from. Also spray a little WD on the lock ring And use a flat tip file and hammer to get it around to unlock. I would sugest getting a new gasket and lock ring, there only a couple of bucks each.When putting the new gasket on take and put some vaseline on it , it will help the new lock ring to slide around in place with less effort.Hope this helps. [img]graemlins/thumbsup.gif[/img]

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post #11 of 18 (permalink) Old Feb 29th, 04, 03:27 PM
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Why would you think it's the sending unit? It sounds like either a wiring or guage problem.

If you disconnect the sender and the gauge goes to 3 o'clock, thats normal, because your sender is a 0-90 ohm potentiometer. An open circuit is way beyond 90 ohms, so it goes offscale high. When you ground the lead (0 ohms) it should go to empty. If it doesn't you've either got a bad guage, or a high resistance connection somewhere between the guage and where you are grounding it. The Gauge is a 0-90 ohm pot, so if it runs out of gas at 1/4 (and it really is empty) then there is about 20 ohms of extra resistance in the wiring between the gauge and the connector in the trunk.

As soon as you disconnect the gauge from the sender, and you still see same odd behaviors when testing then the problem is in the wiring, or gauge, not in the sender. If the gauge operated normally after you disconnected it then I'd say it was the sender. I'd hate to see you waste $75 and go thru the hassle of pulling a gas tank to find you still have the same issues.

Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11

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post #12 of 18 (permalink) Old Feb 29th, 04, 04:57 PM
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try this link for rick's and click on tank sending unit on the left. should be $49 [img]graemlins/thumbsup.gif[/img]
http://www.rickscamaros.com/cgi-loca...241+1084967273

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post #13 of 18 (permalink) Old Mar 1st, 04, 07:36 AM Thread Starter
 
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i say its the sending unit because like the others have suggested, by doing the guage test where you disconnect the brown wire coming from the guage to the rear of the car, the guage goes to 3'oclock, then by grounding it it goes to empty suggesting that the problem isnt in the wiring.

I have been told that i could purchase the sending unit and simply connect the brown wire and ground a black wire somewhere then stand there and move the lever up and down on the sedning unit, if the guage responds then drop the tank, dropping the tank isnt difficult as much as getting that ridiculous whooyah ring to turn is, i looked at a pontiac firbird 67 manual and it shows a special GM tool just for that, i bet the tool is 100 bucks or so lol..

i appreciate everyones feedback, i hope it is the sending unit because, i have a fear of pulling out the dash and guages, main reason is because i dont have patience and i get to agitated, then the next then i know i ripping stuff out ...

thanx god bless..
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post #14 of 18 (permalink) Old Mar 1st, 04, 09:14 AM
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Edawg, yes you can just wire the sender up and move the float up and down by hand. And you can remove the lock ring without any special tools. When ya drop the tank, just spray around the ring with PB Blaster and let it soak for a while. Then tap against the lock ring tabs with a screwdriver back and forth.... first one side, then the other until it starts to turn. You should be alright. Make sure you get a new ring and seal with the new fuel sender if you buy one.
Good luck!

Oh, and relaaaaaax...... stressin' out leads to buying MORE parts because ya broken something. [img]graemlins/thumbsup.gif[/img]

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post #15 of 18 (permalink) Old Mar 1st, 04, 01:59 PM
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Quote:
Originally posted by FASTENUFF:
When putting the new gasket on take and put some vaseline on it , it will help the new lock ring to slide around in place with less effort.Hope this helps. [img]graemlins/thumbsup.gif[/img]
The O-ring seal goes between the sending unit and the tank, not between the lock ring and the sending unit. [img]graemlins/thumbsup.gif[/img]

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