I wasn't just thinking of bending the arm, but of twisting the location where the resistance unit is........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

What will twisting do? It would make the float sit at an angle, which you would have to accomodate by bending the rod, which puts you back where you started. Plus its a lot easier to bend the rod. But regardless, no matter how or where or what you bend, this will change the entire range not part of it. Good thought, but as the infamous seinfeld epside goes, "No soup!"

If any change were to be made to the sending unit, the only thing that would make sense in this case is to open up the resistance unit and change the spacing between the windings to accomodate, because this way you can affect each part of the resistance output individually.

Some more thought, and twisting the resistance unit isn't right either (thought of this before coming back here)

It's more like twisting the whole assembly so that the resistance unit ends up in the middle of the tank.

The problem is unequal arcs of motion for the full 1/2 vs the empty 1/2 of the tank as I think the resistance unit is in the upper portion of the tank

If the resistance unit is in the middle of the tank, there will be equal arcs of motion up and down. So it will read correctly at Full, Half, and Empty. The 1/4 and 3/4 marks wouldn't be exactly right, but would be closer

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I know this isn't going to help anything here...


but has anyone ever considered using an aviation fuel gauge and sender? I'm talking about the capacitance units such as these here: http://www.aircraftspruce.com/catalog/i ... sports.php

I was thinking about this for my car, then I decided to just go with a standard gauge.

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'68 Dodge Dart 4dr Sedan

Emsvitil the resistance unit on the new sender is towards the middle of the tank, whereas the original is mounted on the circular plate. My gut tells me this difference is what is causing this mess.

Theres probably hundreds if not more of these senders out there, they are all over the aftermarket, and I haven't heard of any issues like this with them. Thats what leaves me with an uneasy feeling that it may be something I'm doing or in my particular install, but I've elminated all variables.

I just compared the stock with aftermarket gauge just using some resistors and they measured comparably - this tells me my stock gauge was fine to begin with. I more or less knew this since it was working with the original sender. I just don't know what it is with these replacment senders and this tank....

Just went back and reread everything.

There's a return line. Is it hooked up and is there gas returning?
Wondering if by some sort of bad luck the return gas is hitting the float and making it move.......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Nope, same thing happens with pump not running (car off). Good thought though, that one didn't pop into my mind.

Think you're stuck with off the car testing and watching what goes on with the gauge when you have the sending unit in different positions and then seeing if it makes any sense at all............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Wonder how it would read upside-down.................

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Here is a picture, top unit is my original, bottom unit is the SPI unit. The mopar unit looks similar to the SPI one, without the return line (I added the return line to the mopar unit myself). Has anyone seen a sender like the top one, or know where I can get one like that?

The float arm looks awfully short on the bottom unit, or is that just the angle of the picture.

If it's not the angle, that maybe the problem; you just need to lengthen the arm..........

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Check out the arm on ebay item 8067240818

The resistance unit is in middle, and the arm is longer.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Heres another picture with the arms in the down position, easier to see arm length. I think it is similar to the ebay one you posted, its just an optical illusion



All the replacement senders are like the bottom one, with the arm towards the center. Other then my original I haven't seen another one with the arm in that position

I'll experiment with bending the arm, lengthening etc more once I dig up my old tank and use water. I'm tired of pumping out all the gas and getting under the car to swap senders.

I have a spectra unit the one with 3/8 and 5/16" return line. Mine does basically the same thing. It goes full after just a few gallons its half then just drops to empty.

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1966 Dart GT
4 spd. OD conversion
8 3/4 - 3.55 SG (Sold)

62 Lancer GT
B Body 8 3/4

Johnny, are you sure its a 5/16" return? The bottom unit in the picutre is a spectra fg69b, 3/8" pickup 1/4" return.

I'm such a geek - spare tank is inaccessible, so I improvised. I took an old plastic garbage can and used a holesaw to drill a hole a bit smaller then the plate. Then on the inside I marked 7 levels. I inserted the original sender, sealed it with duct tape, and used hose to fill water to the individual levels, then measured at each level. Did same for SPI sender in stock form, and spi sender with arm bent. Heres what I came up with. Please note these don't correlate with levels in the gas tank but made only for comparison reasons of one sender vs the other.

Left to right, the colums are level #, then original sender resistance, then Spectra sender in stock form, then spectra sender in "modified" form.

1 60 80 62
2 50 80 62
3 35 60 54
4 27 52 46
5 24 44 34
6 21 30 22
7 16 20 9

The first obvious part in the level 1/2/3 region - this illustrates the difference in arm lengths because the spectra sender hits the stop and won't activate that low. No big deal, you can alter the stop or extend the arm (or maybe you can't, due to the way the pickup tube is bent there may be some interference). The big difference is in the level 4/5/6/7 region - on the original sender the differnece between level 4 and 7 is 11 ohms. The differnece in the spi sender amongst these levels is in the 30's.

I returned the spectra senders, getting those to read right seems beyond hope. The dealer/mopar one is a bit better it seems, thats the one I'm running in the car now. Maybe I'll pull that one out and play around with it on my next days off. I'm also investigating using the original sender unmodified and just running the return line into the fill tube in the trunk.

The thought of going to a fuel cell has also crossed my mind but thats going to introduce a slew of other problems on its own.