# gas gauge mishap



## danthepontiacman (Jul 5, 2008)

ok well in light of the earlyer post a while back i changed the sending unit on my 66 tempest to a new stanless steel one for 66 and 67 gto tempest lemans and it still didint fix the gas gauge so i found out the one on a old 67 lemans dash i got out of a junk car was good, tested it cleaned it and changed it and it worked or seemed to, me and a friend drove around 60, or 70 miles anf it stayed on full (21 and half gallon tank) well when i got home i was curious if it was working so i wiggled the wires on the connector at rear of gauge and it started going down but it went to like just under a querter of a tank and now i wiggle the wires and it still dont go back up, ive checked all connections on sending unit, rear body connector and front body connector but still only one wire on gauge is getting a signal, i can use the pigtail from the old dash out of the 67 and a 9 volt battery ad make the gauge go either way bepending on what wire i got on the ground and what wire is on the hot on the 9 volt batter so the gauge works, any ideas has to whats going on? are there any other connections im unawair of?by the way changing the gauge fixed the old problem with the gage staying on 3/4 tank even when full and bounceing to empty then to full when driveing so this is a new problem:willy:


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## pontiac (Mar 6, 2011)

full means the sending wire is open, if wire is grounded, then gauge shows empty. So look for break in wire or poor connection.


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## dimitri (Feb 13, 2009)

I would replace both connectors that plug into the back of your gauge. It sounds as if those could have opened up/rusted and not giving you a solid connection. Also squeeze a bit of dielectric grease into the new connectors. Unplug all of your connectors and do the same with the dielectric grease starting at the fuel tank working forward.


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## danthepontiacman (Jul 5, 2008)

Well I floors the conveyor on the back of the gauge over so only the power side was hooked up and I ran a new wire from the gauge to the sending unit and it went on to empty but when I unplug the wire from the sending unit the gauge gos to full like normal so is it the gauge or the new unit from opg?


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## Rukee (Feb 8, 2007)

Sounds like the gauge is responding normally.


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## danthepontiacman (Jul 5, 2008)

well im glad the gauge is working seeing has it came out of a cluster that was in a 67 lemans conv. that had been sitting in a junkyard for 30 years with the top down but now i guess seeing has i ran a new wire and it did the same it cant be the wireing so is there any way to test the unit itself with a meter?


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## danthepontiacman (Jul 5, 2008)

Well I used a ome meter and put one end on the terminal on the sending unit and the other end on the ground wire were it hooks to the ground and it got full ome so looks like it's getting grounded under the dash somehow if I'm doing this stuff right


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## Rukee (Feb 8, 2007)

If you can pull the wire off the sending unit and the gauge goes to full, then ground the wire and the gauge goes to empty, then the wiring and gauge are fine. It's the sending unit in the tank that's at fault or possibly a ground problem at the sending unit.


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## likethat (Oct 5, 2007)

If you can take out the sending unit from the tank. Put the ohms test to the sending unit on the wiring post and move the arm for the float up and down and see if your ohms go up and down. That is all that a gas gauge is, an ohms meter.

I like to test the sending unit before I put the tank all the way in. I like to make sure that there is at least 1 gallon of gas left when the gauge reads empty. That way I have time to get to the gas station. I have the tank on the ground under the car and in the same position as it will be when bolted in with the car level. Run temporary leads to the wiring and fill the tank with a gallon of gas. I do not put the retaining ring on yet. I adjust the arm by bending it till the gauge reads empty.

I had a 74 Ford Grabber in High School that when the needle just touched the empty line it was all the way out of gas. That gauge wasn't lying when it said empty. You were walking.


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## Rukee (Feb 8, 2007)

"E" does not meen 'Enough'. :seeya:


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## daveh70 (Sep 4, 2008)

What happens if your rotate the connectors that plug into the back of your gauge? By that I mean swap them. Also I believe you'll see a connector with wire that's on the driver's side of the trunk at the sail panel. The wire then continues to the tail lights. Try disconnecting and then connecting that connector at the sail panel.


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## likethat (Oct 5, 2007)

Rukee said:


> "E" does not meen 'Enough'. :seeya:


Exercise?


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## danthepontiacman (Jul 5, 2008)

(Exercise) is the word used to describe fitting me, a 6'4 250lb. man under the dash of my tempest without removeing the bench seat first:willy:


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## danthepontiacman (Jul 5, 2008)

ok well i got a new sending unit, hooked the wires up to it and moved the lever by hand and it went to full like it should and back down like it should so me and my dad installed it, i put 10 gallons in it and its reading just under 1/4 of a tank=/ i put the ground wire on same place it was and same place i tested it, what gives?


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## Rukee (Feb 8, 2007)

was there any gas in the tank to begin with?


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## freethinker (Nov 14, 2009)

danthepontiacman said:


> ok well i got a new sending unit, hooked the wires up to it and moved the lever by hand and it went to full like it should and back down like it should so me and my dad installed it, i put 10 gallons in it and its reading just under 1/4 of a tank=/ i put the ground wire on same place it was and same place i tested it, what gives?


if it went to full when you had it out it doesnt sound like the problem i had but here is what i found out on my 66 after two sending units. there are two sending units that look identical. one is a 30 ohm and one is a 90 ohm if you use the 30 ohm one by mistake it will not go over about a quarter full on the gauge.
the sending unit acts as a ground for the gauge. you can test them with an ohm meter. it should read 0 at empty position and 90 ohms at full.


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