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Fuel tank and gauge update and ideas needed

Well quater tank sounds about right..19 gallon tank and I put in about 5 gallons ish..will check the wire..good call..thanks.
AL
 
Try running two 14g wires of different colors from the sending unit to the gauge. The ground wire is connected to the output tube of the sending unit (secure with a temporary gear clamp) and the other wire to the electrical terminal. Now make the same connections at the dash but using the new wires temporarily. If no response check the ohms at the end of the new wire for a variance indicative of the amount of fuel in the tank. If this is correct or there abouts the problem lies at the gauge end of the circuit. Sometimes the arm on the sending unit has to be bent or even lenghtened to reflect the difference from empty to full which can be difficult to do once in the tank. I set mine up with the sending unit mounted in a slot on a piece of stiff carboard with the exact outline of the tank drawn on it. I found that it did not register until the arm was almost half way up. Bending the rod gave me a reading of "full" when the arm was 2/3rds up. Obviously this unit was a repro piece of junk so I trashed it and bought a good one. Problem solved.
 
AL I hope you get it working, another thing you could do to check the accuracy of the gauge is pickup three resistors of the values I posted above and one at a time put them in the circuit without the sender hooked up. Attach one side to the sending unit wire and the other to good ground and see if the gauge reflects the correct reading. Yatzee do tell us the skinny on what brand and where you purchased the sending unit that worked for you.
 
Got the cluster out and have power to the gauge..I put my test light on the one side and get a nice bright pulse of light the other side is a bit dimmer... but it made the gauge go to just below half tank. I put a jumper from ground to one of the screw holding the circuit board on thinking ground issue but that did nothing.
AL
 
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Yes one side is positive from the voltage limiter and the other side goes to ground through the sending unit. If you connect a ground to the other side without the resistor it will peg very quickly and more than likely burn up the element in the gauge unless your very fast at removing the ground but a risky way to test the gauge for sure.

- - - Updated - - -

Also to check the element you can put an ohm meter across the studs on the gauge
should be around 11 ohms or so. If your gauge is toast shoot me a pm if you want I restore and repair them.
 
Thanks for the tips Bee..ohm meter set to 200ohms I am getting 11.1 to 11.5 on the fuel gauge and 12.2 on my temp gauge if that helps.
Ran a new wire from back of gauge to the sender and still only moves a 1/8 inch.
AL
 
Sounds like the sending unit is inaccurate as usual with the after markets ones. Add a few more gallons of gas and see if the gauge goes up.
 
I can't see it being the sender...when I bought the car I thought that was the problem, so really the tank has seen three senders two of which were new and still not working LOL.
Hooked a AA battery to gauge and it went to 1/4 tank
I will see if any of my buds have a fuel gauge I can use and run some jumpers see what happends.
Thanks for the tips everyone...its no fun working on them if you don't learn something.
AL
 
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It would kill me to have to buy a thrid one..the last one came from National Mopars so I know the quality is there.
Like beekeeper said maybe I will ad more gas and see if the ohm reading changes...if it does then the sender should be working...right? LOL
AL
 
That sounds logical. I must have read 100 threads on as many forums about this and the only 2 solutions were to have the gauge calibrated to the new sender or bend the tube down incrementally until you're satisfied with the reading on the gauge.

There was one guy who opened his rheostat and found a poor contact. He fiddled with it and it worked afterwards. Seems it made good contact half way around then lost contact the further the float arm moved.

Here's a link to trouble shooting:

http://www.moparfins.com/Repairs/Fuel_Gauge_Repair/Fuel_Gauge_Repair.htm
 
I have read that 20 times LOL
Both senders were checked before I put them in the tank and both made the gauge read correctly, empty, half and full..checked the floats and no holes. Put sender in the the tank and the float is not binding on anything.
Power at gauge both sides..power at sender unit..hooked AA battery to gauge and it moves to 1/4..man this has me beat!
AL
 
That is what I was thinking the first time..then with the old tank and new tank I compared them looked inside the tank and the float sits fine.
Long story with this but my temp gauge went for a carp as well. I did have another one from 73 Charger and used some jumpers from the dash gauge to the other temp gauge and it read so maybe I will try a different gas gauge hooked up with some jumpers and see what happends.
Let you know..thanks again
AL
 
Hey Al, does your gauges power off a printed board ?,had a problem board on a 68 rallye cluster that I had to change.Your getting 5 volts to the gauge with no ground?
 
What do you mean no ground...I ran another ground off the cluster Rick just to be sure...
Hooked up the other new sender that was in the tank with some jumpers and the gauge reads..I am so ready to burn this car LOL
AL
 
Found this thread on Moparchat of a guy who had the same problem same car as well but can't figure out what he means..anyone care to have a go:

the problem is solved.

there was a problem with the placement of the float and when it was in the tank the float could not get past the boyancy point to float in the right direction. as i have said that i could feal it float inide the tank when i was putting it in, well that was it moving on the wrong side of the swing. adjusted the arm and now it works. sometimes the answer is so obvious that you miss or over look it. so i walked away colected my thoughts, all three of them, and then went back at it with a clear head. found the problem by finding the angle the sending unit sits at in the tank and then placing the sending unit in a bucket of water. the float then moved on the wrong side.

I emailed him but this thread is over 5 years old and he has not posted since.
AL
 
Hey Al, glad you solved the problem.A pcb on a cluster I had would not allow the gauges to ground unless I used a jumper.
 
Not solved yet Rick gotta figure out what the guy meant in his post..
"could not get past the boyancy point to float in the right direction"
"the float then moved on the wrong side."
AL
 
This is a long thread, are you still at the point to where when it's installed in the tank it does not read past 1/4 or goes to 1/4 then drops to empty or are we passed that yet?

Also got a question, is the sending unit advertised as stainless steel or is the tank? I ask because some advertised stainless steel is not truly steel. so when you think you have a good ground to the unit you really don't. you can check with a magnet. Just something else to consider, I mean its either a bad ground or nothing it has to be one side of the circuit.

If you know you have good 5+ volts to the gauge and it read when you bench tested it out of the tank with a hand made good ground then think about it once in the tank and it doesn't read? has to be the something there not grounding or you have a break in your body that is interrupting the ground back to the cluster. some where the ground isn't getting through.

bending rods etc is one thing when it's not reading all the way full or not going to empty etc not reading at all is not a rod bending fix.
 
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