My next little problem - gas gauge!
September 30th, 2011, 08:22 AM
#1
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Location: Canada
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My next little problem - gas gauge!
OK so the gas gauge always read a bit high when full.
Today it is full right.
How hard is it to get to the sending unit in the tank on these cars (67 Delta 8)?
Anything underthe dash that traditionally goes ie the gauge etc?
Thanks
Today it is full right.
How hard is it to get to the sending unit in the tank on these cars (67 Delta 8)?
Anything underthe dash that traditionally goes ie the gauge etc?
Thanks
September 30th, 2011, 07:32 PM
#2
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Join Date: Jun 2009
Location: southeastern Michigan
Posts: 14,163
I had to replace the sending unit on my '67 Delta. You have to drop the tank. It cannot be gotten at without doing this as it is mounted in the top of the tank.
Here's what the tank looks like out of the car.
Here's the sending unit:
Here's the sending unit disassembled:
Here's what it should look like, assembled and complete with the sock filter on the bottom, which had partially deteriorated on mine.
The float, which is that black thing that looks like a hockey puck, slides up and down on the shaft. It has metal contacts on it that complete a circuit that runs up and down the shaft.
Sending units are just variable resistors, and the position of the float on the shaft sets the resistance. Zero ohms is Empty, 90 ohms is Full.
In my case, the main problem I had was getting the float to move freely up and down inside the canister. I think this design is one that is basically destined to have problems at some point.
These are not reproduced. I found that a sending unit for a '72 Buick LeSabre, which I'm sure fits other GMs of that year, but I searched for the Buick part, is a drop-in replacement. It has an extra line that you'll need to cap off unless your car has A/C, in which case you'll use it.
Now, about yours. When you say it's "full right," what do you mean? On the "F." Past the "F" and pointing at 3 o'clock or something like that? Does the gauge work at all?
If your gauge isn't working, you should check the circuit and make sure there isn't a break somewhere. An open in the circuit will be the equivalent of infinite resistance and cause the needle to go way past the F mark.
If this is the case for you, then first get under the car and check the ground for the sending unit. Two wires come off of the sending unit. The black one, which is the ground, goes forward and attaches to the body up under the car in front of the tank. It's an area where there can be corrosion and dirt, and if the ground isn't making good contact, the result could be a gauge pegged past F.
If the ground is OK, check the other wire, which is orange and goes rearward from the tank and connects to the wire coming from the gauge in the area behind the truck lock mechanism. You have to poke around down there in the area above the center of the bumper inside the trunk. You'll see wires for the taillights, and you also should find an orange one coming from the direction of the tank. It connects to the wire coming from the gauge through a little black connector. Pull that apart and touch the side coming from the gauge to ground. With the ignition on, the gauge should immediately go to E. When you break the connection, the gauge should go back to way past F.
If your gauge behaves this way, then there is nothing wrong with the dash unit or the wiring going to it, and the problem is in the sending unit.
If your gauge does work, but it goes way past F when the tank fall and no lower than, say, 1/4 when the tank is empty, then the problem is still likely the sending unit. It has probably deteriorated, and the resistances have increased. If it does work, though, and you just have to remember that the 3 o'clock position is full while 1/4 is equivalent to Empty, you might just want to live with it. Taking down the tank is not difficult in the absolute sense, but it's not a walk in the park, either. At least, with the way things are, you have some kind of indication of the amount of fuel in the tank.
Whatever your situation, overall, and based on my experience and the design of the sending unit, I'd say that, if you're having problems with the fuel gauge on a '67 full-size Olds, the odds are 90% or better that the problem is in the sending unit.
Here's what the tank looks like out of the car.
Here's the sending unit:
Here's the sending unit disassembled:
Here's what it should look like, assembled and complete with the sock filter on the bottom, which had partially deteriorated on mine.
The float, which is that black thing that looks like a hockey puck, slides up and down on the shaft. It has metal contacts on it that complete a circuit that runs up and down the shaft.
Sending units are just variable resistors, and the position of the float on the shaft sets the resistance. Zero ohms is Empty, 90 ohms is Full.
In my case, the main problem I had was getting the float to move freely up and down inside the canister. I think this design is one that is basically destined to have problems at some point.
These are not reproduced. I found that a sending unit for a '72 Buick LeSabre, which I'm sure fits other GMs of that year, but I searched for the Buick part, is a drop-in replacement. It has an extra line that you'll need to cap off unless your car has A/C, in which case you'll use it.
Now, about yours. When you say it's "full right," what do you mean? On the "F." Past the "F" and pointing at 3 o'clock or something like that? Does the gauge work at all?
If your gauge isn't working, you should check the circuit and make sure there isn't a break somewhere. An open in the circuit will be the equivalent of infinite resistance and cause the needle to go way past the F mark.
If this is the case for you, then first get under the car and check the ground for the sending unit. Two wires come off of the sending unit. The black one, which is the ground, goes forward and attaches to the body up under the car in front of the tank. It's an area where there can be corrosion and dirt, and if the ground isn't making good contact, the result could be a gauge pegged past F.
If the ground is OK, check the other wire, which is orange and goes rearward from the tank and connects to the wire coming from the gauge in the area behind the truck lock mechanism. You have to poke around down there in the area above the center of the bumper inside the trunk. You'll see wires for the taillights, and you also should find an orange one coming from the direction of the tank. It connects to the wire coming from the gauge through a little black connector. Pull that apart and touch the side coming from the gauge to ground. With the ignition on, the gauge should immediately go to E. When you break the connection, the gauge should go back to way past F.
If your gauge behaves this way, then there is nothing wrong with the dash unit or the wiring going to it, and the problem is in the sending unit.
If your gauge does work, but it goes way past F when the tank fall and no lower than, say, 1/4 when the tank is empty, then the problem is still likely the sending unit. It has probably deteriorated, and the resistances have increased. If it does work, though, and you just have to remember that the 3 o'clock position is full while 1/4 is equivalent to Empty, you might just want to live with it. Taking down the tank is not difficult in the absolute sense, but it's not a walk in the park, either. At least, with the way things are, you have some kind of indication of the amount of fuel in the tank.
Whatever your situation, overall, and based on my experience and the design of the sending unit, I'd say that, if you're having problems with the fuel gauge on a '67 full-size Olds, the odds are 90% or better that the problem is in the sending unit.
Last edited by jaunty75; September 30th, 2011 at 07:36 PM.
September 30th, 2011, 09:09 PM
#3
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Join Date: Aug 2011
Location: Canada
Posts: 132
Excellent info mate. My gauge was reading past the F about half way between the F and the hot light. I never let it get much below a 1/4 tank as I figured it might be skewed or something.
Yesterday I filled up but have noticed that the gauge has not dropped even though I have put about 80 miles on it. The needle also seems to be further right ie closer to the hot light and, as mentioned, not leaving that location.
With power off, should the the needle normally drop to E?
Thanks again
Yesterday I filled up but have noticed that the gauge has not dropped even though I have put about 80 miles on it. The needle also seems to be further right ie closer to the hot light and, as mentioned, not leaving that location.
With power off, should the the needle normally drop to E?
Thanks again
October 1st, 2011, 02:55 AM
#4
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Join Date: Jun 2009
Location: southeastern Michigan
Posts: 14,163
No. With no power to the gauge, the needle could come to rest anywhere. I wouldn't take any meaning from where it comes to rest when the key is off.
From your description, it sounds like your sending unit is not, shall we say, up to factory spec. But the fact that it works at all suggests that there is no wiring problem between the gauge and the tank. I would still check the sending unit ground, though, as an intermittent ground could possibly cause what you're seeing.
From your description, it sounds like your sending unit is not, shall we say, up to factory spec. But the fact that it works at all suggests that there is no wiring problem between the gauge and the tank. I would still check the sending unit ground, though, as an intermittent ground could possibly cause what you're seeing.
August 1st, 2012, 09:13 PM
#5
Im wondering on my 69 olds y my fuel gauge with key in on position pegs to full but key off it slowly i mean slowy falls to about 3\4 but pegs full w key on and i know for sure its low on gas!>>
August 2nd, 2012, 07:56 AM
#6
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Join Date: Jun 2009
Location: southeastern Michigan
Posts: 14,163
If the gauge pegs on full or beyond and stays there when the key is on, you have, as I said, an open circuit. If you've not yet done any investigating, the first thing to check is the ground wire coming off the sending unit. It attaches to the body under the car just forward of the tank, and it's in an area where a lot of crud can build up over the years and affect the ground. Find this wire (it should be black) and check the quality of its connection to the body.
Another test is to find the other wire coming off the sending unit (which is probably orange) where it connects to the wire coming from the gauge on the dash, usually in the area behind the license plate or inside the trunk in the area of the trunk latch. There is a connector here that can be pulled apart. Ground the wire coming from the gauge and turn the key on. The gauge should go to E and stay there. If it does, your gauge is fine as is the wiring from the gauge to the rear of the car, and the problem is either in the ground as described above or in the sending unit itself.
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