Fuel gauge. Again.

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67 Dart GT

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I've read that this topic has been beaten to death but I'm still in need of advice.

Fuel gauge in my 67 Dart reads just under half on a full tank and quickly drops to read empty when less than half a tank is used. Sending unit float flooded I thought. New sending unit in and same thing. Old unit appeared within acceptable tolerances actually, little off, so I replaced it anyway since I had a new one.

Checked at tank with a test light. Solid pulse. Grounded sending unit wire failed to make gauge do anything but go to a little over quarter full.

Temp gauge works fine. So I'm thinking gauge itself unless anyone has any other thoughts.

Thanks in advance. Appreciate your guys input!
 
See what the resistance of the tank sender is. Compare that with what the gauge "is doing."

Is it evidently only the fuel gauge? It still could be loose connections, etc, in the system.

The general opinion is that repop senders are not worth a ....... for accuracy
 
What I did was pull sender out of tank, rig up some wiring to set the sending unit on thr ground. I got a 0 to 1K variable resistor. I wired the resistor into the hot wire to unit. I adjusted till I got the desired results on the gauge, then without moving the setting, removed the variable resistor, read the value with a VOM, then just purchased a carbon resistor matching the value on the variable. wired in the resistor somewhere in the line to the tank. works great now.
 
There were a few very technical responses in another recent fuel gauge thread.
A fault between limiter and circuit board was the root cause of that limiter putting out high voltage and both gauges going to full. Owner bent the male spades on the limiter a little and poked it back in. It's cured, for a while atleast.
So now that you know your problem isn't at the sender, you'll need to check that gauge, its connections to the circuit board. The mounting nuts are its connections and have been found loose before. I wont go into what the inside of that gauge might look like and why the needle cant travel as it should until we know the fault isn't on the outside of the gauge.
What puzzles me in your comments, full tank of fuel ( 10 ohms through sender ) gets half full reading, then wired to ground ( 0 ohms resistance ) gets just over 1/4 tank, or did you mean 3/4 tank ? Zero resistance should have taken the needle to its fixed stop, a bit beyond the 'F' . Only thing that I can think of is voltage supplied to the limiter. Like maybe the engine running charging voltage is 12+. Then only switch on is a bit less than the full 12 volts. Less in is less out. Hope this helps.
 
I believe the old sender is a repop, as is the new one, so I'll try the resistor route if tracking down and cleaning all the system connections doesn't work. Thought since I had a reading that wiring was good but stands to reason it still could be a poor connection somewhere. Thank you both!
 
Yep only a little past quarter full is the best I got when grounded, and when hooked up outside the tank moving the float to full by hand. When the tank was actually full the gauge only ever stayed at half full for a very short time. I've been all over the tank connections so start at drivers kick panel I'm guessing and head to the cluster.
 
67 Dart GT said:
I believe the old sender is a repop, as is the new one, so I'll try the resistor route if tracking down and cleaning all the system connections doesn't work. Thought since I had a reading that wiring was good but stands to reason it still could be a poor connection somewhere. Thank you both!
Click to expand...

If the bends in the senders tube are identical, they are both reproductions. The sender with several bends didn't appear until 1975 or 6. Tube of the 67 sender would have only 2 bends, 1 about 30 degrees down and another 90 degrees.
I'm looking to get a used very wrong aftermarket linear sender to play with.
If you now have a spare for cheap ?
 
Thanks for all the info. The resistor idea. Would not grounding the sender wire have done the same thing - but pegging the gauge?

My connections all appear ok. Gauge itself is all that's left I think. Cluster wasn't cooperating the other day when I tried to get it out. I did it once before years ago but somehow it got more difficult. Ha

Gonna hang on to the old sender till I get this figured out....
 
Grounding the sender wire does not tell you anything at all about the accuracy of the voltage to the gauge, the wiring/ pc board/ gauge connections, the accuracy of the IVR or the gauge unit itself.

It is nothing but a quick check that works sometimes to separate the problem between a completely bad sender and "the rest" of the system.
 
I have run into this a few times on different cars. It was the ground, the gage, and the float sticking. 1.I grounded both ends of the ground wire to bare metal. 2.The gage was replaced . 3.The gage was removed and sprayed with WD40 on the moving parts (needle sticking) and cleaned. Used float gage lubricant, water remover called Sea Foam? or whatever I had in the shop. Does it do this when key ignition is turned to both LF and RT sides?
 
I have a 68 Dart GTS and both my temp and fuel gauges aren't working. I replaced the VR, and now when I turn the key, nothing happens (to engage the fuel gauge) but when I turn on the headlight switch the fuel gauge pegs to full and then some. Is the headlight circuit different then the ignition circuit as far as that goes? I have yet to replace those stamped "nuts" for ground on the circuit board (which I also replaced). Any ideas?
 
You either have a cross (short) in the harness somewhere, or a grounding problem in the cluster. On my 67, the contact fingers that engage the VR were not making contact. The cluster must be grounded as does one terminal of the VR You really SHOULD add a ground pigtail from the cluster to the dash frame or column support

Check this thread

Printed circuit pins repair

here, post 16 if the new software works

Printed circuit pins repair

DSC_1421_zpsa3d00147.jpg



My own soldering was not as neat. But it works

vrsolder-jpg.1714668983
 
I am working on finding a nut to fit the console studs, but in the interim, I forgot to mention that with the old VR in, there is no change, but with the new one, the fuel gauge climbs with the headlight switch on (parking light position and head). Is it safe to at least assume that the old VR is bad?
 
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