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Car (57) ran out of gas and guage was showing about 1/8 tank left. Put in two gallons and now guage is nearly at 1/4. What do I need to do to make the needle go back down towards E?
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Re: C1 Gas guage adjustment
1. Take the sender out, and bend the arm to make it read the way you want. Right now, your gauge is off by 1/8 of a tank. It's going to take a lot of experimenting with bending that arm to make it more accurate than that. If, in the course of experimenting, you screw up the sender, you'll need to buy a new one. There's been many reports that the new senders are not very accurate.
2. You could also resolve never to drive around with the tank less than 1/2 full. -
Re: C1 Gas guage adjustment
If you decide to take the sender out, first make sure that it is "talking" to the dash gauge by sweeping the float arm through its full range while watching the gauge. Make sure that the float assembly is well grounded or you will get erroneous results.
If the gauge is not responding fully, it could be one of four things: 1) a poor ground, 2) a bad signal wire, 3) A bad or out of calibration sender or 4) a bad gauge.
Sending units like those for gas and temperature operate by changing the electrical resistance to ground from 0 (perfect connection) to some higher resistance which varies by manufacturer. The varied current is then interpreted by a magnetic movement in the gauge that should result in an accurate reading. But factor in the age of the car and wiring, the liklihood of poor ground connection in a fiberglass car and the use of aftermarket parts, and it won't take much for a SNAFU.
So, if after sweeping the float through its range, and messing with bending the float arm still does not cure your problem, you might have to correct the resistance being delivered to the gauge. Experts on this board can confirm the range but I think the sender should report 0 ohms with the float all the way up (full) and 33 ohms with it all the way down in the empty position. To test this, put one lead of an ohm meter on a ground point of the sending unit and the other on the signal post with the signal wire removed and car off (best done on the bench) and sweep the float through the range. You can "force" the gauge to the empty position sooner by putting a resistor (a cheap item at Radio Shack) of a few ohms in the signal line from the sender to the gauge but this could screw up the top end gauge reading. You might see a sudden drop from full to say 3/4 once the float moves off of the 0 ohm position. If you want to skip all of the above, just buy a 5 or 10 ohm resistor for $2 and put it between the sender signal wire and the gauge post under the dash which should put it to empty quicker. Then fill the car up and see what you get.
You could also check your gauge in a similar fashion by the use of a potentiometer (variable resistor) that has a similar resistance range. Disconnect the signal wire from the sender, connect one side of the potentiometer to the signal wire and the other to a good ground. Turn the key to on to power the gauge, then rotate the "pot" through its range. At some point the gauge needle should go from full to empty. When you reach empty. Turn off the key and disconnect the pot and measure the resistance. That should correspond with what the sender is giving in the empty position. If not, one of them must be corrected to match.
This is kind of like a Mission Impossible assignment. So, if you decide to accept this mission, please don't forget that you'll be working near an open fuel tank so be careful!Comment
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