Fuel Cell level sender

[cudabob496]

I put a 12 gallon JAZ fuel cell in my cuda, but the level sending unit seems to give really inaccurate indication on my autoguage level gauge. When I fill the cell half full, the level guage indicates just above the "E". I'm pretty sure everything is grounded correctly, and the ohm ratings are properly matched. The level guage indicated correctly when the sending unit in my gas tank was hooked up. Any thoughts as to what may be wrong? Thanks

[MEK-Dangerfield]

Since all was well with this set-up in your gas tank, my only thoughts are about how the sending unit is mounted in the fuel cell. Might it be twisted so that the pick-up tube is not at the bottom? IF this is a different sending unit that was in your gas tank, then I definitely suspect a mis-match here as far as resisitance ratings go. This one seems too high.


  Mike

[cudabob496]

After a lot of troubleshooting, JAZ sent me a replacement sending unit, and unfortunately it  performs the exact same way as the one that came in my 12 gallon fuel cell. I've made sure everything is hooked up right and grounded properly. I measured ohms per inch of magnate travel in each sending unit, and I hooked up each unit to my fuel gauge. My fuel cell is 10 inches high, and with the sending unit float magnet at 5 inches above the botton of the cell, my autoguage fuel gauge reads at the top of the "E". It should be reading 1/2 full. At 7 inches above the bottom of the fuel cell the guage reads 1/4 full, instead of almost 3/4 full. There is not the accuracy to tell when I might run out of fuel. JAZ insists that the sending unit is working as designed, while I insist that it is a poor design. One design problem is the sending unit float magnate bottom position is 2 inches from the floor of the cell, and the highest position is about 1 and 1/4 inch from top of cell. In my opinion, it is a poor application of a poor design. Maybe the signal strenth from the JAZ sending unit is too weak, even though the resistance is correct. Maybe the unit needs a stronger magnet? JAZ has been kind enough to give me a $75 dollar refund on my $210 purchase price. I will look for a more accurate guage, or try to make one myself. In the mean time, I will get some rubber and aluminum plate and plug the hole in the top of the cell. As I mentioned earlier, my autoguage fuel guage is a Chrysler 70 - 10 ohm, and worked great with a newer sending unit that was in my gas tank.

[Chryco Psycho]

I wish I had a solution for this , all the sender does is create a resistance to ground , adding an inline resistor would make the gauge read even lower at 1/2 tank I believe so you need to lower the resistance across the sender to read correctly which would require removing some of the windings & spreading the remaining ones out evenly 

[cudabob496]

I noticed there are all kinds of sending unit designs at Summit.com, and elsewhere.  And, the sending unit in my gas tank caused the fuel guage to work perfectly. So I think this one from JAZ just doesn't generate enough signal or something. In other words, my original sending unit in the gas tank would give, say, a 60 ohm resistance in the circuitry, and the fuel gauge would indicate say 1/8 full. But this JAZ unit can give a resistance from 70 to 44ohms, and the gauge barely gets off empty.  The JAZ unit is a reed switch and magnet design with 9 pickup points, while the stock unit is float on a pivot arm, which gives a uninterrupted variable resistance. Oh well, time to see what else is out there.

[MEK-Dangerfield]

I feel for you, as it seems you know what the problem is here. The 10-70 Ohm range is definitely correct. Can you possibly post a pick of the sending unit you are dealing with? The fuel cell units are foreign to me. 


  Mike

[cudabob496]

The one in the upper right of the page

http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&N=0&Ntt=sending+unit&Ntk=all&Nty=1&D=sending+unit&Ntx=mode%2Bmatchall&Dx=mode%2Bmatchall&searchTerm=sending+unit&x=21&y=10

[cudabob496]

Well folks,
You know how you have good days and bad days wrenching in the garage, well, I fabbed up a plate to block the hole where the sending unit was. To the bottom of the plate I attached an L shape aluminum braket, and attached the potentiometer and float from my original gas tank sending unit. Also ran the signal wire through a small hole drilled in plate. Will plug with RTV. Just tested it, and it's working great. Hot dog! May have to fab a small cage to protect the float from the foam in the fuel cell, but right now I've got the foam crammed out of the way. Thanks for all the help!
(This was easy to do, and I've seen used Mopar sending units on Ebay for 5 to 10 bucks. Make your own sender instead of paying $100 or $200)

[MEK-Dangerfield]

     

[Bullitt-]

Guess this goes to show there was something wrong with the sending units from Jazz.. Shouldn't have to be this complicated...maybe check with the gauge mnf. & see if they have a recommendation for a source if you don't want the OE type.

[cudabob496]

Good idea, thanks.