samuelcosmo76

I finally put a new tank in my dart a few weeks ago, but now the gas gauge reads empty when there is still a half a tank left.....but it does show full when the tank is full, it just goes down too quick.

Any idea as to why this would happen? Are the new senders calibrated differently or something? Part number FG69A at advance auto parts if that helps. Waddaya think?

67 GTX

Ok, I recently did the same thing and have the same problem. You also replaced the sending unit right?
I've found out that the new sending units aren't calibrated to all of the gauges. I have not fixed the problem, but have been told that adding a resistor may solve it. I will need to try that.

I've also talked to over people who have changed the tank and sending unit, and they all have the same problem.

John Van

Make sure you have a good ground! Do you still have the old sending unit? If you do ,measure the resistance with a volt,ohm meter and compare it to the new one,should be 10-70 ohms. Were the float and rod the same length and angle as the new one? Was the new fuel tank the same capacity and depth? The fg69a is the right part number for a dart. Well at least it reads empty when half filled and not the other way around!

samuelcosmo76

@67 I don't think adding a resistor would help, because it reads empty when its full, so it would be the other way around. The only thing I can think of is maybe the ground isn't solid, and there's some resistance there.

@John...I'm gonna try that next time I fill it up, I do still have the old one.

Unless the ground is what's causing the problem, I'm thinking I'm gonna have to take the sender out again and bend the float....calibrate it myself. Granted, it will then read full for longer than it should, so if anyone has some better ideas, hit me with em!

BuckNeccid

You might get a better calibration by extending the rod with the float on it. Since it reads empty when it's half full, it could be the rod is too short and not reaching the gas. Maybe take your old sendning unit, cut the rod off it , then hit someplace like Lowes and get a threaded sleeve. Cut some threads on your old unit arm, cut off the new float and thread that one as well, and then screw your old one on the new one, and adjust the length as needed. I'd cut it as long as I could at first, and then slowly remove more until it's where it needs to be.

You're right, by bending the rod, it might let you know when it's actually empty but it's going to read full for a long time before rapid drops in fuel levels. The extended rod should cure that.

samuelcosmo76

That's a good idea....I think I'm gonna try that.

samuelcosmo76

They don't call me Sam Schiff for nothin'! :-p

I found a way to calibrate the sender. With the gauge reading dead E, I took a variable resistor, and hooked it between the sender and ground, and moved it until the gauge read half (or a little under), because I know when my gauge is on empty, she only takes about 8 gallons.

I measured with a multimeter, and it was about 50 ohms. I wired in a 50 ohm resistor, and viola! Gauge now reads past full on a full tank, just like it used to.

Keep in mind, the test for the sender is shorting it to ground, and seeing if the gauge shoots to full. That's why this works. Also, 50 ohms is an oddball value....so if that's the value that works for you, it might be best to pick up an assortment from radioshack as opposed to ordering one.

67, give it a try!

67 GTX

You are a genius!!!! I gotta give this a try. I'll let you know how it goes.

samuelcosmo76

yeah let me know! I feel like the sender should come with a few resistor values to help calibrate it!

samuelcosmo76

No good! The gauge reads about 1/8th more than what I have by the time it gets down to 1/4. So, I'm gonna swap in a 60 Ohm instead of the 50, and that'll fix it right up!