JUSTIN Posted March 7, 2001 Share Posted March 7, 2001 my gas gauge is a roller coaster. it goes to empty for a few minutes then goes to correct then back to empty. no rhyme or reason. I am guessing its a short. when the tank was out of the car and I was manually working the float lever it was perfect. assuming that it is a short, I was planning on running a wire directly from the sender to the guage to test it. where do I plug into the guage?<P>second question: I notice the tank has about 2 gallons left when I run out of gas. what kind of pickup should I use. Is there a flexible hose that would lay in the bottom of the tank? what about a pickup filter, do I need one and where can I get one? with only a 20 gallon tank and 12 mpgs I need all the tank I can get. Link to comment Share on other sites More sharing options...
Sled Posted March 8, 2001 Share Posted March 8, 2001 Hiya Justin<P> I have a 65 Electra conv. My gas gauge did act up, but it was the ground wire to the sending unit/tank. Check that out. Corrosion and rust dont help make a good contact. Good Luck!<BR>Jim Link to comment Share on other sites More sharing options...
JUSTIN Posted March 8, 2001 Author Share Posted March 8, 2001 i dont have a ground wire. there is just one wire coming from the sender. maybe the tank is suppose to ground it? Link to comment Share on other sites More sharing options...
Guest John Chapman Posted March 8, 2001 Share Posted March 8, 2001 Justin,<P>There should be a ground wire from the sender unit to the chassis/body. The tank itself will not provide grounding due to squeak mat and gaskets on the sender unit.<P>JMC Link to comment Share on other sites More sharing options...
JUSTIN Posted March 9, 2001 Author Share Posted March 9, 2001 i will try to ground the sender unit by adding a wire to one of the screws that hold it to the tank. then I will ground the wire to the frame. sound right? Link to comment Share on other sites More sharing options...
Guest John Chapman Posted March 9, 2001 Share Posted March 9, 2001 'S awright, Augie!<BR>Good luck. Link to comment Share on other sites More sharing options...
DENNISWEBER47 Posted March 15, 2001 Share Posted March 15, 2001 THE WIRE FROM THE GUAGE TO THE STUD ON THE TANK UNIT CANNOT BE IN CONTACT WITH ANY PART OF THE TANK, OR IT WILL NOT WORK (JUST GOT MINE WORKING AGAIN). THE EARLY CARS HAD AN INSULATOP STRIP THAT GOES ON THE STUD FIRST ( TO INSULATE ) THAN THE WIRE FROM THE GAUGE, THEN THE NOT. THE INSULATOR STRIP THEN LOOPS OVER THE STUD AND ANOTHER NUT HOLDS IT IN PLACE. THE STRIP NOT ONLY INSULATES THE SENDING UNIT STUD FROM THE TANK, BUT WHEN LOOPED OVER AGAIN, IT IS SUPPOSE TO PREVENT DUST, DIRT AND ROAD SALT FROM CORRODING THE TERMINAL AND CONNECTION. ADDITIONALLY, THERE IS NO "EXTRA" GROUND WIRE FROM THE TANK BODY TO FRAME. SHOULDNT REALLY NEED ONE. COULD BE THAT THE NUT ON THE STUD HAS LOOSENED UP OVER TIME... HOPE THIS HELPS DENNIS WEBER BCA#24134 Link to comment Share on other sites More sharing options...
Guest Posted March 16, 2001 Share Posted March 16, 2001 Dennis, What year is your car?<BR>The GM cars from the 60's and 70's have a ground (black) wire from the sending unit that goes to the chassis for ground. This black wire may bolt directly to the chassis, or go through the wiring harness to the bolted location. All electrical devices must have at least two connections. Ground counts as one connection. Maybe earlier cars ground through the tank to the frame, and you do not have a wire, but there is a connection to ground, or the gage will not work.<P>Frank DuVal Link to comment Share on other sites More sharing options...
Guest Posted March 16, 2001 Share Posted March 16, 2001 Justin:<P>Quick test ( if you can get to the sending unit terminals without removing the tank!):<P>Unplug the wire from the insulated terminal of the sending unit. Start the car and see what the gage reads, empty or full. It should not read mid way. Drive the car and see if the gage reading changes. If it does, the problem is an interrmittent short in the wiring harness. Now ground this wire. The gage should now read opposite of when the wire was disconnected. If the reading does not change, the problem is in the wiring harness or gage. Now drive the car with the wire grounded. If the gage reading changes, then the wire from the gage to the sending ubit is opening up, either a broken wire or a corroded connector along the way.<P>Frank DuVal Link to comment Share on other sites More sharing options...
DENNISWEBER47 Posted March 18, 2001 Share Posted March 18, 2001 FRANK, MINE IS A 53 SUPER 56R. THE GROUND MUST HAVE BEEN INTRODUCED LATER. I TOOK MINE ON A 250 MILE TRIP WITHOUT THE GAUGE AND DECIDED IT HAD TO BE FIXED, BEFORE THIS SPRING. IT TOOK ME THREE TANK DROPS TO FIGURE OUT WHAT I WAS DOING WRONG ! Link to comment Share on other sites More sharing options...
JUSTIN Posted March 19, 2001 Author Share Posted March 19, 2001 Frank:<BR>I couldn't get to the sending unit without removing the tank so with all this grounding stuff questions. I just drilled a hole in the flange on the side if the tank and attached a wire to it and then to the frame. but it didnt do any good. half way to work it starting working again. so I take it that the ground is not the problem unless I am not getting a good ground with the new wire or I have to ground the sending unit and not the tank itself. wednesday I will follow your testing steps but I plan on dropping the tank also, so I should be able to ground off the screws on the sending unit. Link to comment Share on other sites More sharing options...
JUSTIN Posted March 22, 2001 Author Share Posted March 22, 2001 ok folks. I lowered the tank and insulated the top of the nut on the sending unit. it works!!!! I just put a big piece of duct tape on top of the nut so it wouldnt contact the bottom of the trunk. the ground is coming from the extra wire I attached to the flange earlier. Hooray!!!! Link to comment Share on other sites More sharing options...
JUSTIN Posted March 23, 2001 Author Share Posted March 23, 2001 booo!! thats the opposite of hooray. my gauge worked all day then it went dead the next morning. now it works. so it seems I do have a short. it was probably multiple problems (short and ground). those are the hardest to find. well if I wanted to run a new wire from the tank to the gauge, what route would I take? Link to comment Share on other sites More sharing options...
The Old Guy Posted March 23, 2001 Share Posted March 23, 2001 After reading all the posts on this subject, I went out and pulled the tank on my 57 Buick . I put a ground strap directly to the sender and the guage works ,but only half way. When you put the sending unit back in the hole, be sure the lever is free. I think mine is rubbing on a baffle ,as it only goes half way up. At least it tells me when I am runnin low ,so that is a big help. The next time I get ambitious ,I'll pull the tank and fix it right. Link to comment Share on other sites More sharing options...
Guest Posted March 24, 2001 Share Posted March 24, 2001 Chances are your sending unit is not rubbing on a baffle. It has two circuits; one for the top half of the tank and one for the bottom. Don't ask me why. Anyway, one of the circuits likely isn't working.<P>John Link to comment Share on other sites More sharing options...
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