fuel guage

[roger01]

my tank is full ...but the guage reads just under half full ...ive checked the ground at the tank and it is a new sending unit what else could it be .....?

[Plumcrazy]

Unplug the sending unit and ground the connector terminal to see if the gauge goes to full

What year is your car?

[Ghoste]

Check all connections between the sender and guage as well.

[roger01]

ive grounded the wire guage goes to full......arent the only connections at the tank and the guage ,they are all hooked up

[Ghoste]

The harness that runs to the rear of the car has a connector to go to the dash harness.  There should also be a fuse for the instrument panel.  It isn't likely that there are problems in those connections but if you run out of places to check...

[Plumcrazy]

ive grounded the wire gauge goes to full......arent the only connections at the tank and the gauge ,they are all hooked up

If you grounded the wire that attaches to the fuel sending unit, then the gauge and wiring  back to the tank are okay.

You have a bad ground or a bad sending unit.

Hook the wire back up to the sending unit.  Take a piece of long wire and attach it to the negative battery terminal.  Touch it to the sending unit while someone watches the gauge.  If it goes to full you have a bad ground.  Remember, the sending unit grounds to the fuel line so the fuel line has to be grounded also.

If the gauge doesn't change when you ground it with the wire, the sending unit is the problem.

[JimShine]

Can there be any other issues? My car does the same thing (but reads dead on half tank when full). I have a brand new sending unit which I have double grounded (just to be sure) and all in the cluster section is fine. I wondered if my guage needs to be calibrated, or if my voltage regulator on the rear of the cluster was getting funky. I believe my temp and oil guages are also approximately 50% off.

[Plumcrazy]

Can there be any other issues? My car does the same thing (but reads dead on half tank when full). I have a brand new sending unit which I have double grounded (just to be sure) and all in the cluster section is fine. I wondered if my gauge needs to be calibrated, or if my voltage regulator on the rear of the cluster was getting funky. I believe my temp and oil gauges are also approximately 50% off.

A voltage limiter problem would show up on all the gauges except the alternator so that could be your problem. Try a known good one. Very unlikely all three gauges would be off by the same amount in the same direction.  Remember, the cluster must be grounded also. 

Try grounding the wire that attaches to each of the sending units and see if they go to full scale.

[roger01]

i grounded fro the battery and it does go to full........im thinking you might be right that the fuel line itself isnt grounded ....iused plastic covered fasteners  im going to try grounding it tomorrow ....thanks

[Plumcrazy]

i grounded fro the battery and it does go to full........im thinking you might be right that the fuel line itself isn't grounded ....iused plastic covered fasteners  im going to try grounding it tomorrow ....thanks

Replace the plastic covered fasteners and your gauge should work great.   

[roger01]

i grounded the fuel and checked all connections ....still reads half full

[Silver R/T]

I heard you might have to calibrate your fuel sending unit

[Plumcrazy]

If the gauge reads full when you provide a good ground with a ground wire then you have a ground problem not a calibration problem.

The strap between the sending unit and fuel line is in good condition right ?

[Brock Samson]

mines been doing that consistantly, since 1984,..
ive been compleatly thru the entire fuel system incl. new tank, float, sender, wiring, pad, straps and anything else remotely related,..
even a new guage..
still shows a quarter ful when it's topped off...

[roger01]

IT IS .....nice and tight and made it really scratch into the line .....

[roger01]

can i hook another fuel guage under the dash somewhere ?....is it just two wires ?

[Ghoste]

Do you mean another Charger one to verify it or an aftermarket one?  There are aftermarket ones available but I think there is a little more to it than just hooking it up to your existing wiring and driving away.

[Nacho-RT74]

it could be just the fuel sender unit point bended.

Inside the unit there is a copper 90º angled arm with a point welded to the floater arm runing throught a coil what is a variable resistor. Is not rare that the copper bends and doesn't arrive to top since rust can stuck it somehow.

Just remove the sender unit from tank and check on an inner box that contains this assembly. is easy to check since it has a hole to see inside and check for correct function.

[Plumcrazy]

IT IS .....nice and tight and made it really scratch into the line .....

If the gauge read correctly when you used the jumper wire between it and the battery you are not getting a good ground thru the fuel line for some reason.  Attach a wire to the sending unit and run it to wherever you can get a good ground.

[roger01]

ive done that as well ............whats the best way to get a good ground ...

[Plumcrazy]

ive done that as well ............whats the best way to get a good ground ...

Drill a hole in the nearest piece of sheet metal and attach the wire there.  The body has to be grounded or else you would have a lot more things not working.

[hulter]

The ohms at tank sender range from 10 full to 73 empty.  Test ohms at tank and then with the sender connected to harness, test the ohms at the sender pin connector (one of 5 pins that conect in single plug to cluster) at clluster.  Should be same.  Also nice thing to ck continuity in the sender wire from tank to same connector at cluster.

If ohms are correct at both spots for gas level and guage is off, then need recalibration of gauge- they use magnets to do it.

[Ghoste]

I thought that was just for speedometers (magnets for recalibration that is)?

[TylerCharger69]

I had the same issue when i first bought my car.    I learned later on down the road that the float had little pin holes in it, making it too heavy to pass the center point.   I replaced all that crap with an aftermarket sending unit and gauge anyway.

[roger01]

my sending units brand new and has been tested

[histoy]

If the gauge reads empty and full as described earlier, and the tank sending unit is grounded well, and the gauge still reads improperly, then you will have to adjust the float level setting for the tank sending unit.  I've had to do this on several new sending units... not just Mopars.  My buddy recently had to do it to his Super Bee.   He siphoned all the gas out of his tank, and removed the sending unit.  Then he put in 10 gallons of gas, so the tank was half full.  Then he inserted the sending unit to see what the gauge read.  He pulled the sending unit and adjusted the float angle until the gauge read 1/2 full.  Once this is done, just reassemble, fill the tank, and it should read full...Brian

[johntpr]

None of the repro sending units work correctly and give an accurate reading out the box.  I re-used my original after trying 3 different repros.

[roger01]

it looks like thats what i have to do ......it just scares the hell out of me working on an empty or half empty tank ....can i do this with the tank full..?

[roger01]

and buy the way ....what do you do ...? just bend the float arm...

[histoy]

Messing with a gas tank isn't my favorite thing to do either, but yes, you bend the float arm so that it will move the sending unit switch in the direction needed to change the gauge setting.  It will probably take a few tries to get it right...Brian

[smokinrt]

i grounded the fuel and checked all connections ....still reads half full

roger,  my restoration guide shows a special ground clamp from the fuel tank to the fuel line.
Good luck
smokin rt

[hulter]

I think it is much easier just to do as I said above:  "The ohms at tank sender range from 10 full to 73 empty. "  If you are getting the same ohm reading at cluster plug from sender and and the tank /sender and it is 10 ohms when full or 73 empty, you are calibrated at the sender and at the plug.  If the gauge is not reading properly then the gauge is out of calibration- happens due to the poor design of the stock voltage limiter.  Can replace with digital limiter.  May still need to  re-calibrate gauge- can send to Redline or one of teh other gauge places.

[Ghoste]

None of the repro sending units work correctly and give an accurate reading out the box.  I re-used my original after trying 3 different repros.

Just out of curiousity, did you check the reading on those senders before putting them in or did you just run them out of the box?

[roger01]

no i did check them .....they were right on to what they should be

[Ghoste]

That doesn't seem right.