Fuel tank sender that works?

Perrybones wrote: I have a 70 Jav SST, a 69 AMX and a 73 AMX. The 69 probably has the original fuel tank sending unit in it since its all original and low mileage, that one works OK. The 70 has one of the aftermarket units that works horribly (after fill up goes to 3/4 mark for a little bit, then it races through the middle levels then sits at 1/4 for most of its life)  I am getting tired of thinking the fuel is low and getting a gasoline bath with these lousy new gas pumps.

That's interesting because that's how my original sending unit works in the 70.
My 73 even after gauge and cluster replacement still tops out full at 3/4 on the gauge and spends a ton of time at the quarter mark.
And it's not a replacement. 
The 70 tank has been off, cleaned, all connections checked and cleaned up........ so it must be a cluster issue. 
The 73 - well, who the heck knows because the previous owner was a wiring guru - he was great at hacking, cutting, splicing by twisting, and leaving things out. 

Would be interesting to see how that could be tied to the AMC fuel gauge in the cluster - most of us don't want to hack up the cluster to change gauges, but if an accurate SENDING UNIT could be found, we'd take notice. My Eagle gauge is actually quite accurate, but then AMC changed to the magnetic type gauge before Eagle came out so they did a better job as long as your wiring was good. And - no regulation needed for them like the early gauges.

OK, Mopar_guy - I'll send you a couple of tanks and sending units and clusters to get things all calibrated. Or maybe just drop my cars off some day.

Mopar_guy wrote: I did this back when I swapped the Magnum engine in and used an AMC1 tank with a Javelin level unit I bought (all stainless from eBag) the ohms range was 12 to 85 ohms instead of 12 to 60 ohms that the gauge is calibrated too. I shortened up the range of travel to fix that problem but it still wasn't right. I figured out that the float arm was to long so I shortened it by 2" and it reads right now. Anybody that puts in an Spectra AMC1 tank, they don't make a sending unit for it so you have to use a Javelin sending unit and recalibrate it to read properly but the same holds true for any of the new sending units out there.

Just my thoughts to add in helping others with calibration... i removed the original wire wound resistance board, cleaned it up carefully, as the wire is tightly wound in a smooth progressive way. Too much pressure will make each winding off and bunch them to tight against each other. Used gas resistant gasket adhesive to secure the windings to the edges of the board, so any long term action with the wiper arm will not distrurb the accuracy set in the windings.

I noted by the wear pattern on the wire, that the wiper arm travel does not go all the way from one end to the other, so with old board replacing the one in the new replacement sender, you can match how far the arm travels by checking how the pickup slides along the wear pattern.

Once the tabs are adjusted, you can flip the board over an use the unused bwck side of the board as to be a good as new.

Once i get around to the sender and tank setups, i can post how to adjust the arm, but it will be based on the original factory resistance board, not the out of spec resistance board on the aftermarket senders.

I can post my resistance board images of the wear patern with measured length for reference. This way some who will be adjusting the stop tabs and adjustments to carefully shift the resistance wire windings, to at least get the wiper action in the ball park with resistance set closure to factory specs.

Here are the images for reference. Notice the shadowy mark on the first image... that is the mark left from years of rubbing under travel, on the pickup arm. Second image has my addition of the blue line under the mark to assist in locating start and end points of travel. The length is 15mm of travel in a slight arc. Bottom image is the reverse side, it just so happens that the original side had a lamination bubble, that may effect how the pickup on the arm reacts to reading resistance.







Edited by 304-dude - Jun/22/2019 at 6:01am