fuel sending units , c'mon

[Ghoste]

No one seems to know for sure.

[70sixpkrt]

I ordered one from Kramer. They check the calibration before they shipped it out. Some people have no problems and some do with there units.

[Ghoste]

Let us know how you make out with it.

[70sixpkrt]

I won't be able to install it for about another month.

[Lennard]

Don't the new sending units available from Kramer's solve the problem?

See John L´s reply in this topic.

[poppa]

mine didn't....yet

[70sixpkrt]

Well I just installed the sending unit and, wait for it, it reads FULL.  

[Lennard]

Well I just installed the sending unit and, wait for it, it reads FULL.  

With an empty fuel tank? 

[70sixpkrt]

With almost 3 gallons in it, it read empty. Put 16.10 gallons and it read full.

[Lennard]

Great, thanks for the review. I'll by a Kramer when I get to that point.

[BananaDan]

Hey all, just found this thread. My Kramer's sender is still fine, it's been in the car for almost a year. I just filled the car up yesterday and it went up to full.

[Brock Lee]

Anyone try one of the Spectra "premium" sending units? I put one in, but haven't finished the car up yet. I needed a new unit anyway, so I threw the extra couple bucks hoping it would be at least a little more accurate. The claim is it reads 80-10 ohms.

[Ghoste]

I could be wrong but my understanding is that its less a case of the range it reads than it is how the range is calibrated from one extreme to the other.  The oem ones travel from one point to the other would be a curve if you could see the electrical signal and the repros travel in a linear fashion.  If that makes sense.  Or if my understanding is even correct for that matter.

[Dino]

I think you have it right.   

The original senders would have a resistance of roughly 24 ohm with the needle on the halfway mark whereas the new units are more in the 40 range.  So the gauge will read correct when at empty or full, but not inbetween.

[Brock Lee]

I totally get what you are saying.

In other variable resistors, the resistance from point A to B can be equal, but the taper from A to B can be different. Most commonly used tapers are linear and log tapers.

My guess is the originals were a log taper whereas new ones are  linear taper. A linear taper variable resistors resistance is proportional to where the contacts are located on the strip. Log tapers are very offset. The factory probably chose the offset taper to accommodate the angled bottom of the tank. It takes less fuel to move the float in that area than above the angled portion.

[Ghoste]

So why is it so impossible for them to use a log taper today?

[Pete in NH]

I totally get what you are saying.

In other variable resistors, the resistance from point A to B can be equal, but the taper from A to B can be different. Most commonly used tapers are linear and log tapers.

My guess is the originals were a log taper whereas new ones are  linear taper. A linear taper variable resistors resistance is proportional to where the contacts are located on the strip. Log tapers are very offset. The factory probably chose the offset taper to accommodate the angled bottom of the tank. It takes less fuel to move the float in that area than above the angled portion.

The originals were log taper and there is no reason reproduction units can not be made the same way. It is slightly easier to wind the resistance wire on in a linear manner but, with the right cam on the winding machine a log taper can be done in a very repeatable manner.

I can only think its a combination of laziness, indifference and ignorance on the part of the company's reproducing these parts. It's not like this is an unknown issue and you would think by now it would have been corrected.

[Ghoste]

I just don't get it.

[Brock Lee]

Is whomever that is ordering these specifying log taper? It may just be a case where the manufacturer is making what is ordered. That is something that should be easily available for the asking. The only issue I can think of is the manufacture is currently using a linear taper on other products, so a log taper would be outside their production norm. It still should be doable even for an upcharge. But I still wonder if they even were asked for such a detail. Most likely they are just given a modern sending unit to knock off with the old resistance readings as a spec and that is it.

Anyone figure out if the originals were regular log, or reverse log tapers?

[Mike DC]

 
I recall hearing years ago that the Mopar repro sending units were getting GM-style internal components.  I don't know if that is true or not. 

[Brock Lee]

Could be. I would not be surprised to learn GM used linear taper. Every GM I have ever owned had a gas gauge that moved faster through one half than the other. GM may have set the standard in reproductions, and the companies making them may not even know better.

Anyone know who made the originals? Bendix? Federal Mogul? Briggs and Stratton?

[Ghoste]

Not sure but we did have one member here who approached the oem supplier about getting repros made by them and I think A) he didn't get a lot of response from potential buyers (the deal as I understand it kind of necessitated paying up front but I think with the current state of repro fuel senders everyone now has a wait and see approach) which led to B) the oem supplier wasn't all that interested in such an insignificantly tiny market.

[Lennard]

Not sure but we did have one member here who approached the oem supplier about getting repros made by them and I think A) he didn't get a lot of response from potential buyers (the deal as I understand it kind of necessitated paying up front but I think with the current state of repro fuel senders everyone now has a wait and see approach) which led to B) the oem supplier wasn't all that interested in such an insignificantly tiny market.

http://www.dodgecharger.com/forum/index.php/topic,108809.0.html

[Brock Lee]

Not sure but we did have one member here who approached the oem supplier about getting repros made by them and I think A) he didn't get a lot of response from potential buyers (the deal as I understand it kind of necessitated paying up front but I think with the current state of repro fuel senders everyone now has a wait and see approach) which led to B) the oem supplier wasn't all that interested in such an insignificantly tiny market.

Yeah, I would expect an OEM to want to make and sell a minimum quantity of units. That is the nature of the beast. They are used to making runs of thousands of units at a time, being paid at once. No time to mess around with a small batch and then have to trickle income in..It isn't worth the time. You have to find someone willing to put up the cash and be willing to take a long ass time to recoup their investment and start to make a profit.

If the new Spectras read empty and (at least close to) full, I am happy. I will get used to the in between swing.

[Mike DC]

  
This is stupid.  Why doesn't some repro parts company just get a correct batch made?  Word would get around fast if somebody had the correct ones in stock.  We shouldn't have to be doing it this way ourselves.