Fuel sending unit issues!

[GTX.JCW]

What is going on:

From the time we acquired the GTX it has had difficulty displaying anything more that about 1/2 tank of fuel.

The first thing I did was replace the sending unit, purchased through Classic Industries. No change, same indications.

Next came the new instrument panel with new Autometer fuel gauge, with the correct resistance for MOPAR's. Same problem.

This week, we cleaned the area around the tank and added a ground wire from tank & from the sending unit to chassis. Same problem!

Then we ran the ground from the sending unit all the way up to the battery ground. Same fricking thing!

Now, we are contemplating another sending unit, hopefully one made in the USA rather than China....

I have seen NOS units for $200+, but they are only 5/16" units and I need a 3/8". Also found dozens of units for anywhere from $30 - $150. Does anybody know which of these is a reputable manufacture and vendor where I can get one that will work?

Also, if I have left out a troubleshooting area, please let me know...

Jeff

 

[PUNKN8R]

Sounds like a grounding issue do you have a good ground from motor to body and or chassis ?? It could also be a dash board grounding issue as well. I had a similar problem as well I added a body ground from battery then added a chassis to body ground.
The dash board was the grounded to body as well not sure which one of the added grounds solved the problem but it has been working great so far (Knock on wood )! GOOD LUCK!!!

 

[hunt2elk]

The newer sending units are far from perfect to put it mildly. I've heard that because the range is non linear, people are having a hard time replicating them - not sure if this is true or not. Did you ohm the new sender out to see what it is doing and at what position in the arc? It took me 3 before I got one that worked the way I wanted it to when I restored my Road Runner a few years ago. And I still ended up bending the arm somewhat. I just bought a Spectra for my Charger project and it seems decent, but of course I haven't tried it in the tank with fuel yet.

 

[GTX.JCW]

I can't say for sure, but I believe we did ohm it out prior to install. I have been searching out different manufactures and no one seems to say "Where" their product is built.
I did see Spectra and most likely will go that way. I will ohm it out to see where it falls in the arm swing.

Also, I will be adding a 12ga wire from the ground side of my gauge and the tank/sending unit to the chassis to make sure I have a good ground.

Thanks

Jeff

 

[kiwigtx]

Remove your new sending unit and compare a few details with the old one.
1. test the ohms when FULL & EMPTY
2. test the ohms when float arm fully down, and arm fully up (hopefully same readings)
3. measure the length between the Pivot point on both and the centre of the float itself

In my experience, the length of the float arm can be as much as 1/2" longer, which of course prevents full travel on the float - resulting in a less than full reading on your gauge.

I don't think you have ground issues, I think it is the length of the float arm....or your float is full of gas.

Check it out and get back to us here :headbang:

 

[GTX.JCW]

The old unit is long gone...

Since the unit that is in there now is relatively new, I don't think the float is leaking, but that could be possible. As for the float arm being too long, I like that as a better possibility.
If someone out there has a NOS or an original sending unit that is out of the car, could you measure the length of the float arm and let me know its dimension??

Thanks Kiwi

Jeff

 

[Dennis H]

Been through this before. It can't be fixed. Ohms. Schmohms. Wires. Grounds. I wish I had the original sending unit I thru out. New one won't read over 2/3. While we are at it, don't buy this related stuff from Mopar Ed in the Central Valley. Nothing but heartache and delays including the tank delivery. Take the mileage and fuel around 150 miles or so.

 

[moparmarks]

Try a Spectra sending unit. Made in Canada and is suppose to actually work un-like all the others.

 

[hemidon1]

Ive cured many of these by bending the arm down--give it a try--I also tried everything you have done & met with the conclusion that "everything I know is wrong"by bending it down the reostate will reach full --if the senders in your hand & grounded to the chassis--& the wire is hooked to your sender then by moveing the arm by hand the gauge always works correctly--with that knowledge you know it is able to read--so I bent the arm down & it does cure the 2/3 full reading--give it a try

 

[69Bee]

Did you take the tank out to replace the sending unit? If so, did you adjust the tank straps properly? If not, the tank is not in the correct position, and won't read properly. I replaced the trunk in my Bee, and made the mistake of sitting my fat a$$ in the trunk when I welded the panels in. :head_smack: Yea, I know, MORON... lol. Anyway, when I went to adjust the new tank, I could not get it all the way up (really? :giggle, and the gauge only read 2/3's full.

 

[GTX.JCW]

When we changed the unit, the tank stayed in the car.

I will give the "bend the arm" a shot next week.

Thanks to all!

Jeff

 

[kiwigtx]

The old unit is long gone...

Since the unit that is in there now is relatively new, I don't think the float is leaking, but that could be possible. As for the float arm being too long, I like that as a better possibility.
If someone out there has a NOS or an original sending unit that is out of the car, could you measure the length of the float arm and let me know its dimension??

Thanks Kiwi

Jeff

I just measured what I believe to be the original from my '70 GTX.
From the center of the pivot pin to the outside of the float arm hook = 3-3/4" (float has been tossed ages ago)

If you were careful and have a good feel for things, you could shorten the arm by a series of small bends - and measure the resistance (ohms) as you go, to make sure it works OK. That way you can vary the level of fuel required to make the float reach its maximum travel - thus giving best chance of the gauge reading FULL.

Hope that helps

 

[themechanic]

The old unit is long gone...

Since the unit that is in there now is relatively new, I don't think the float is leaking, but that could be possible. As for the float arm being too long, I like that as a better possibility.
If someone out there has a NOS or an original sending unit that is out of the car, could you measure the length of the float arm and let me know its dimension??

Thanks Kiwi

Jeff

My "new" sender has a brass float that looks brand new. But, shaky, shaky, and you hear liquid inside. Hmmm. I replaced the "new" sender with another one.

But, this time I put the new float under water and no bubbles. So, in the tank it went.

 

[monaco66coupe]

To fix mine I removed the sending unit, ran a hot and a ground to it, and slowly moved it by hand in short Increments. As I did my Son would call out the level. I was able to affect the fuel level on the gauge. I found a rough spot toward the top of the travel, cleaned it,and bent the rod some as suggested earlier. I hate to say it, but a GM float fits the rod(EEECHHH!) Now mine works perfect. I have another original as well, if it would help you out.

 

[bigmanjbmopar]

Wondering if you you pulled the connector off the sending unit and just grounded it with the key on?(the wire to the gauge) If the gauges /wires are all good then you should see the gauge go to full. Also you can take any sending unit and do the same thing / test outside of the tank. just ground any edge of the unit and then with the wire to the cluster connected and key on operate the sending unit lever and remember the response is SLOW so don't expect to see it peg full when you raise the unit arm to full in two seconds.

If not, check wire to rear of car runs on drivers side under carpet to behind seat area. meter for opens or breaks.

 

[GTX.JCW]

Wondering if you you pulled the connector off the sending unit and just grounded it with the key on?(the wire to the gauge) If the gauges /wires are all good then you should see the gauge go to full. Also you can take any sending unit and do the same thing / test outside of the tank. just ground any edge of the unit and then with the wire to the cluster connected and key on operate the sending unit lever and remember the response is SLOW so don't expect to see it peg full when you raise the unit arm to full in two seconds.

If not, check wire to rear of car runs on drivers side under carpet to behind seat area. meter for opens or breaks.

The wire harness to the rear of the car is brand new. That being said, I will use this bit of info when I get to work on the car next week...


Many thanks to everybody, especially Kiwi for the pic of his sender!!!


Jeff

 

[RRunner1968]

I can answer this one. My gauge and sender were original and worked fine. One day the gauge quit so I replaced it. Still didn't work so I ordered a sender from Year One, the gauge still wouldn't work. After driving it for 2 years and running out of gas on occasion, I found the wire I had broken in my trunk. Another 2 years of the gauge reading half a tank when I filled it. Put the old sender back in and the gauge reads properly again. This is on a 68 GTX.

 

[wannadrag]

Guys the new sending units are crap and I did try the spectra and it was crap also.Tried the mexico one from Dixes Mopar parts,crap also.The Chinese one from vans was the one that read 2/3 when full so I used it.

 

[bigmanjbmopar]

I have a question? You mention the original gauge only showed 1/2 a tank then you switched to an after market one? Do you have anymore info about the cluster itself? Do you know if it was broken or modifyed at all in it's life? I ask because some gauges have adjustments were if you know you have a full tank but it only shows 1/2 there is a small adjustment wheel inside the gauge that can fix that.

 

[Garys1969RR]

Replaced the non working sending unit on my 69 RR with a GTX one. Then at full it would read 1/4 tank. So did remove the sending unit and hooked up the wires and a good ground. Son in the driver seat, lifted it up, showed a half tank. Had to put a big bend in the arm to get it to read full on the gauge when the float was lifted up to full position. Now when I fill it up, the gauge is pegged to the full mark. But it goes down quickly . Shows empty when there is prob 3/8 tank left. Lol. Good enough 4 me!

- - - Updated - - -

Just bought a 67 Satellite that had the fuel tank replaced. Gauge wouldn't work at all. Put on the ground strap ( goes fuel line from tank, around rubber hose, to body fuel line. This grounded it properly, and it started working. The straps are available. Now when I fill it up, it reads a little over 1/2 tank. Ha ha. Now will need take it apart, son in the driver seat, and get out the vise grips! 60s technology. It sorta works. Good luck.