another fuel sending unit question

[JoeGrapes]

    Ok, this is getting to be a real pain. I replaced the dash gauge with a new one. I replaced the voltage limiter with an electronic one. I replaced the sending unit with a new one I bought on e-bay. I even installed a dedicated ground wire for the sending unit. I still can't get the gauge to read right. The gauge reads full when the tank is full but will drop off fast so when the tank is half full the gauge reads empty.
    I've read a lot of comments about the repro sending units not reading like the originals. Is this a common problem that everyone has when they need to replace a 40 year old sending unit? I just can't believe that every new sending unit acts like this. Every place I looked that sells sending units all seem to sell the same one that's made by Spectra.

[TelisSE440]

It may be possible to happen. I still have the original and it reads excellent. Check the resistance of the sending unit with an ohmmeter and compare it with the factory readings, you'll find them if you search here. If the readings are different, then things are difficult, if not then somewhere a high resistance makes the readings false. In the occasion of different readings, I would bend the floater carrier when gas is in the middle of the tank (not to get spilled or anything) and insert until I was happy with the reading, but this is a difficult task, and you may not get the result you like.

[tman]

My repro unit did the same as yours when it was new.  I just lived with it.  It was much better then my old one that read full all the time. 

[1 Wild R/T]

What amazes me is all the Repo sending units have been junk for years, people complain but nothing changes... At one time a few years back a vendor out of Georgia worked with the OE manufacturer to supposedly get a run of senders for A's, B's & E's done... He hung his $$$$ out there to try to get a better product... What did he get? The OE re-boxed the same Chinese crap....

I used a NOS sender in my Challenger, works perfectly....

I have a repo for my Coronet... I have concerns but since it's not on the road I have no idea if it works or not...

Funny thing, I needed a new sender for my beater 87 Toyota P/U, it was still available through Toyota, it works perfectly, even the low fuel light... Why can't the aftermarket build a sender that works....

[JayBee]

When you said "dedicated ground wire", was it from the swing arm to the case like my green one in the picture. Without that modification, the only ground is at the moving shaft that goes through the housing.



Also, when you check the resistance move the arm very slowly, there may be a dead spot on the coil.

[TelisSE440]

When you said "dedicated ground wire", was it from the swing arm to the case like my green one in the picture. Without that modification, the only ground is at the moving shaft that goes through the housing.



Also, when you check the resistance move the arm very slowly, there may be a dead spot on the coil.

Ok Jaybee, I see you perfected this sport! 

[JoeGrapes]

I've checked the resistance of the new sending unit and it's right where it's should be at the high and low end. The problem is the resistance coil of the new units are not like the original units. The new units are more linear with the readings. If you look at the pic above of the resistance you will see the coil is smaller at one end than the other. The new units are the same at each end so the ohm reading when the float is half way along the coil is half way between 10 ohms and 72 ohms. The original units didn't read that way even though each end read the same. My ground is good. If it was bad I would think the unit wouldn't read at all. I guess I'll just have to live with it like everyone else until someone starts making one just like the originals. 

[ShelbyDogg]

What you have to do is transfer the old board and resistor wire over to the new unit. This way you'll have the factory winding in a new holder. The part that wears on the old one was the contact point anyway. You can use a small nut and screw instead of the rivets.

[soundcontrol]

I had problems with mina also. It's 2015, the mechanical design for this unit was used in the early 30's! Why can't someone make an electronic version that don't have any moving parts now.... It should be very easy (and not expensive) to make one that is a direct replacement for the stock one and outputs the correct ohms. Probably because there is not enough profit in it...

[soundcontrol]

Here is a sensor that will work, need no voltage regulator, need no ground in the tank, outputs Volts, just ground the other end of the fuel gauge instead.The only obsticle is to get it mounted right in the tank through the hole in the side, can't be that difficult.


http://www.wemausa.com/sensors/level-Capacitance.shtml

[Bullitt-]

guy over at dodgecharger.com seems to have figured out part of the problem with the repro units ....no easy solution
http://www.dodgecharger.com/forum/index.php/topic,57376.0.html

[JoeGrapes]

I did think about taking the resistance coil out of the old one and using it for the new one but I tossed in the junk before the thought came to me. I also did what the guy from the Charger forums did with his sending unit. I had an older repro unit that I thought was bad so I put exactly half a tank of gas and kept bending the float rod until the gauge read half. It sort of worked but only at half a tank. Kind of like a broken clock being right twice a day. Anyway, I went through all this before I found out all the repro sending units work this way.

[dodj]

Maybe I just got lucky, but I bought a replacement fuel sending unit from Van's about three years ago and it has been flawless. Nice linear reading from full to empty. Actually I did have to tweak the float arn as it was bent a bit and the float would get stuck at empty if you let the fuel get tooo low. So not quite flawless but... close.

[soundcontrol]

Maybe I just got lucky, but I bought a replacement fuel sending unit from Van's about three years ago and it has been flawless. Nice linear reading from full to empty. Actually I did have to tweak the float arn as it was bent a bit and the float would get stuck at empty if you let the fuel get tooo low. So not quite flawless but... close.

I got one from YearOne, its working fine also. Repaired my stock unit, but changed later it just in case.

[JoeGrapes]

I got this unit from Vans also. I don't know why some read right and some don't.