Gauge or sender

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Ok, how about this? Since gauge reads empty at 50 ohms, why not adjust/bend sender wire to read 50 ohms at empty position? Keeping in mind float position in tank. Then see what gauge reads at low and high sender position. What do you guys think, or am I asking for possible destruction of my gauge if there is no ohm resistance to obtain full reading ? Earlier test show only 3/4 full on gauge at full position on sender with what is supposed to be proper ohm reading of 9.5 ohms.
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Well, you are assuming that when the tank is actually full, the sender is actually positioned at the 9.5 ohm full position. Without filling the tank, you'll not know. But I understand why you don't want to.

One of my next suggestions was to bend the float arm so that the resistance is lower lower for a given fuel setting. Bend the arm downward to do this.

But you are still shooting in the dark. It's been suggested twice that you get some resistors to check your gauge. If your sender out of the tank can be set to read 9.5 ohms on one end and 73 ohms on the other, now would be a good time to use the sender as a variable test resistor. Take out the sender, set the sender resistance to each of the 3 specified values in turn, and plug it into the gauge circuit and see where the gauge goes. At this point, it is a pure guess if the gauge is good or not without testing. You obviously have the right skills to do this.

And check that IVR output voltage as suggested so that can be eliminated. The substitution test is good, but not proof.
 
IVR voltage fluctuated between approximately 2 and 6 volts, both my old and new one. I believe I covered using sender as a variable test resistor in post #8. Correct me if I am wrong. Am now having battery charging issues but don't believe that would be related to gauge problem.
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Ahh there it is. I read post 8 but did not get exactly what you were doing. With the gauge only reading 3/4 with the sender moved to full (9.5ohms) then the gauge it for sure off. FYI, these gauges are thermal gauges so the response is normally very slow.

As for your IVR test, what you read is as good as you can do with a meter. The only better way to test the IVR is either:
1) with an oscilloscope, which 99.9% of gearheads won't have or ever need
2) substitute a steady 5 v source in place of the IVR and recheck the gauge.

BTW there are adjustments inside the gauges that can be adjusted. It almost sounds like your fuel gauge range adjustment is off from where is should be. Here is a good explanation; the Mopar gauges are just like these VW gauges.

Electric Fuel Gauges

There are 1 or 2 threads in the electrical section of these forums where someone has had success in changing these gauge adjustments.

Your 1/2 range resistance of 40 ohms or so still doesn't match up to the low 20 ohm range that it should be. I suspect that is in the newer sender.
 
From what I think I understand the 1/2 position on the sender does not necessarily corilate to the gauge showing 1/2 full. Because of the tanks non uniform shape. When fuel level gets lower I will mess with sender more.
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Have established that gauge does work by grounding it at the kick panel connection. Have grounded sender 3 ways from heck with no results. Guess I'm back to the sender.
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What do you mean by grounding the sender? Did you put a ground wire at the connection of fuel gauge wire to the sender, or from the sender flange to ground?
 
Sorry, I wasn't clear on that. Tried grounding sender to bumper, to brake line ( realized later that was pretty iffy) finally grounded sender with a wire to a new screw into the underbody. No change with any of those connections. Am thinking now the problem has to be in the sender alone.
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OK... any fuel in the tank now? Seems like this sender DID register for you to some degree at the start of this thread.
 
Tank should be approximately 1/2 full now. Sender will still move gauge from below empty to very slightly above empty. Going to remove it and see about bending float arm or checking for any other issues I can observe or imagine. When I grounded gauge at the kick panel connector it moved to full.
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Pulled sender again. Bent, twisted, pryed ,pulled and otherwise adjusted float to sender arm using ohm readings from shop manual. Got it set really close.
Hooked sender up to gauge at drivers kick panel, moved float arm from full to empty repeatedly. Gauge operated perfectly .Reinstalled sender in tank .Put in 4 1/2 gallons, gauge rose to empty. Will have to add more fuel to see what happens then. I guess if I fill when it shows empty it will be good, or I have 4 1/2 more gallons to play with.
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Well, sounds like progress. I know that my son's 'Cuda has only 2 gallons or so from dead empty and is getting close to having pickup problems when the gauge reads E, so you might be able to get it better.

Going back to your post #26, if the gauge is empty at 50 ohms sender resistance, and reads only 3/4 at 9.5 ohms sender resistance, and you replaced the IVR earlier with no change, then I suspect the gauge is just plain off. If you follow the link in post #29, it will give you some info on re-calibrating the gauge. 1 or 2 others on FABO have done this with success.
 
Hurrah, added 10 gallons more to tank which should be about 14 1/2 gallons total. Gauge went to full.drove 35 miles and gauge moved to just below 1/2. Added about 3 1/2 gallons and tank was full and gauge showed slightly above full . 4 1/2 gallons in tank showed empty. Think that is as good as I'm going to get it. I will just have to get used to the gauge vs fuel amount. If it stays consistent and I fill at empty I should never run out. A BIG THANKS to all who helped me with this problem.
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