Aftermarket Year One SS Fuel Sender...how to get calibrated?

[303 Mopar]

OK, I've spent about 2-3 hours rebuilding, calibrating, and testing the original sender. It looks like this is a 1/4 increment gauge...the needle should only move to the tick marks during fuel readings and should NOT move past to the "bracket ends".

Have you tested this when its in the tank?  That is my current issue.  The unit work fine outside the tank, but once it is installed I can not get it to work.  I've spent hours on it and can not figure it out.

[Bullitt-]

OK, I've spent about 2-3 hours rebuilding, calibrating, and testing the original sender. It looks like this is a 1/4 increment gauge...the needle should only move to the tick marks during fuel readings and should NOT move past to the "bracket ends".

Have you tested this when its in the tank?  That is my current issue.  The unit work fine outside the tank, but once it is installed I can not get it to work.  I've spent hours on it and can not figure it out.

Pretty simple to test once you determine the sender & the float is good....
Ground the wire going to the gauge & it should peg full, if not the problem is with the gauge or wiring between. Otherwise provide a solid ground to the sender, the OE clamp ground straps can be sketchy.

[kawahonda]

Welp. Got my filter in, plug it up, and decided to test my sender ONE MORE TIME before dropping it into the tank.

Empty, read perfect.

Full, read 1/10 off.

It's enough off where I didn't necessarily have to mess with it, but I thought 'hmm, what if I ever so slightly bent the tang?"

Did so, in the CORRECT direction, and now it's 1/8 off from the full mark. OK, now it's annoying.

I took it apart again and spent another 1.5 hours on it, only to get nowhere.

These would be MUCH easier to calibrate if the tang/band housing was screwed together and not the tabs. Just the subtle act of "fastening" up a box can throw off your Ohm readings +/- 10 Ohms. The EXACT position of the housing can ruin calibration.

But I was never able to get the "full" position to read any lower than 16Ohms now, and that's not acceptable.

So yea, I gave up on it. Ordered a NOS sender unit.

This nightmare should be over soon. At least you can say that I tried my ass off...I probably spent 6 hours trying to perfect the original. They're just so finicky. Tossing it into the "junk" box.

[kawahonda]

The nightmare continues. Let me start from the beginning as of today.

I got in my NOS Mopar fuel sending unit. Same part # as the one I have, but  a newer revision. Grounding strap is a grounding wire. Some other minor differences. Came in a mopar bag dated in the early 90s, which is pretty cool.

I tested the angle at 10, 23, and 74 ohms, as well as the float position compared to the original one. It's seems exact.

I tested the OHMs. Full was 10 ohms, empty was 88ohms. 88ohms is a bit high (gauge won't care about it) but more on that below.

I tested it with the dash gauge. Looked superb. The dash gauge doesn't care about anything after 74 ohms..it positions it all the same.

However, I did notice one difference. The tab for the empty position is much further down compared to the original, therefor, allowing the ohms to go to 88. I bent the bottom tab slightly to where the float rod would still make contact (any more bending it risks the rod missing it). This brought my ohms to 85 or so. Good enough, since again the gauge positions at 10, 23, and 73/74 ohms were pretty accurate compared to the original sender.

See pictures of both gauges. First picture is my float position on the newer gauge moved to 73-74 OHMs exactly. Second picture is the float all the way down to the tab (85 ohms).

I figured it would work just the same...perhaps the float would sit against the bottom of the tank if it's dead empty (which it could never get to). And the float would kick in to the gauge (73 ohms) at the exact correct position as the original since it matches the arc/angle as the original gauge.

Installed the tank, fastened the grounding wire, and plugged in the sender wire.

Poured in 5 gallons. Gauge didn't register anything. Poured in another 5 gallons. Gauge didn't register anything. Lowered the left exhaust and removed heat shield. Made sure that the fuel sending wire was correctly in place. Gauge didn't register. Bypassed the grounding strap and grounded the sender on my own. Gauge didn't register anything. At this point, I decided to check the ohms of the sending unit being that it has 10 gallons of gas...it should read 1/2 full. My multimeter showed 85ohms. Basically is as if the sending unit float didn't move at all.

Yes, I tested the brass float (for about 30 seconds submerged), which is brand new. The sender came with a white plastic one and I removed it in favor of the brass one.

I'm pretty happy that the fuel tank is installed and shouldn't need to come out again. However, it is possible that I will need to remove the sender, which I believe I can do with the tank still installed.

Possible explanations:

1) New brass float has a leak. Unlikely.

2) Sending float arm is in a bind. Unlikely.

3) Sending unit has malfunctioned being that it was on the shelf for many years. Unlikely as it tested wonderfully.

Thoughts?

[7212Mopar]

I have the exact same problem you are having. I am on my second new sender from Mancini. When I ground the plug gauge read full but only slightly moved past empty when plugged in. Ground the sender and still no change. I am working on the trans now so have not play with it much since. Hope you solve it for both of us.

[kawahonda]

Well, you won't believe it....

Just a little jiggle to start it off!

[303 Mopar]

Well, you won't believe it....

Just a little jiggle to start it off!

I'm having the same problem too, but not sure I understand this....

[RUNCHARGER]

The dang arm was hung up.

[kawahonda]

You guys owe me Mopar apparel if this fixes your problem.

I have a theory. While I am using a NOS mopar gauge, I think the same theory could hold true for aftermarket gauges.

If the ARM can swing as low as shown in pictures, then the arm's "hook" can keep the arm/float from rotating upwards initially after fuel is inserted since it is a little "pinched" with the bottom of the gas tank. I have no other possible explanation for how I fixed this last night. My guess is this is only a one-time problem since fuel will never be "empty" in the tank again (the arm won't have the chance to run all the way back down where it was to the tab).

You can use a coat hanger and very gently push it all the way it and run it side to side. You'll feel the sender in there and it's pretty easily to "kick start" the float. Should take a minute or so to assure that you've bumped the float.

I thought it was a stupid idea that was going to have a 5% chance of working last night, but after 15 seconds of moving the coat hanger around (fully extended) I heard something and boom, now i'm in business.

[303 Mopar]

 

The dang arm was hung up.

At this point I will try anything.  Thanks!

[7212Mopar]

Thanks. I will give it a try tonight when I get home. Hope it works for me too but hope there will be no boom. I will freak out and my wife will too.

[7212Mopar]

I tried the cloth hanger but did not have the magic touch to make it work. I had at least 15 gallons of fuel in the tank but the wire felt dry. Is it possible the fuel get vaporized in just a few months in the garage? There are no fuel leaks.

[kawahonda]

If a full-length hanger came up dry (with just enough hook that you can wrap your fingers around it as a handle)...then you ain't got fuel in there sir!

[kawahonda]

Time for an update!

As many of you know, I failed to replace my tank neck rubber gasket. Bad idea. Basically, I'm not able to fill it up past 11 gallons before it leaks.

Today I wanted to verify that my gauge is indeed accurate. I think the answer is "yes" and also "no".

"Yes" in that when my gauge reads empty, the car is empty. The most important part.

From this very low state, adding 11 gallons moves the gauge pretty close to the "F" mark. So for the "full" state, the answer is that it is not accurate. But it actually doesn't matter that much...still probably more accurate than any aftermarket gauge.

This also allowed me to verify how much gas I can put in the car before I run the risk of a gasoline leak. 11 gallons is the answer. During November, I will drop the tank and replace the rubber gasket.

So essentially, how my NOS gauge will likely behave is that 13-14 gallons (maybe even slightly more) will probably read very full (pegged). Adding another 4 gallons to full capacity (18 gal) would probably not cause any needle movement. From 12-14ish gallons to zero, the needle will move across the entire range.

That's damn fine by me. You won't run out of fuel with how this gauge performs.