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Sending Unit - Fuel Gauge

67SniperHockey

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Hey guys - got a “new” working old stock sending unit that I am about to install to fix my leaking sending unit and non-working fuel gauge.

I unplugged the lead wire from my original unit and fed it down to my new unit on the ground just to test it out. Started car and gauge doesn’t move.

I have no reason to believe the unit I got doesn’t work. So what am I missing and what should I check? Wire/gauge itself/specific fuse for gauge? Not sure what to look for I guess. Thanks!

67 Coronet R/T with 440.
 
Hey guys - got a “new” working old stock sending unit that I am about to install to fix my leaking sending unit and non-working fuel gauge.

I unplugged the lead wire from my original unit and fed it down to my new unit on the ground just to test it out. Started car and gauge doesn’t move.

I have no reason to believe the unit I got doesn’t work. So what am I missing and what should I check? Wire/gauge itself/specific fuse for gauge? Not sure what to look for I guess. Thanks!

67 Coronet R/T with 440.
I believe if you ground the sender wire with the key on the gauge will go past full. That tests the gauge, printed circuit and wiring. If the needle doesn't move you have an issue in those areas.
 
if you ground the sending unit and the gauge still does not work I have been told that there is a voltage limiter in the dash that goes bad and will keep the gas gauge from working.
 
Got “new” sending unit installed - double gasket and no leaks. Added a second ground and gauge moves.

however - when I filled it gauge only goes to half full. So isn’t accurate at all.
 
I am interested in the answer to the inaccuracy of the gauge. I installed a new sending unit in my 68 GTX, filled it full of gas and it shows just over a half tank. Sounds like the same problem 67SH is having.
 
I am interested in the answer to the inaccuracy of the gauge. I installed a new sending unit in my 68 GTX, filled it full of gas and it shows just over a half tank. Sounds like the same problem 67SH is having.
That is the exact same issue I'm having on my 69 GTX! If you can figure it out I'll K.Y.A. at State and Madison and I'll give you an hour to draw a crowd!
 
Got “new” sending unit installed - double gasket and no leaks. Added a second ground and gauge moves.

however - when I filled it gauge only goes to half full. So isn’t accurate at all.
If the tank is full of gas, and the gauge only makes it to half-way or thereabouts...the brass float has a hole, and is filled with fuel.
Remove sender unit and repair or replace the float.
 
If the tank is full of gas, and the gauge only makes it to half-way or thereabouts...the brass float has a hole, and is filled with fuel.
Remove sender unit and repair or replace the float.
Wish I knew that before I just installed it - lol! Thanks for the info. Any idea of where you can buy a new brass float?
 
Wish I knew that before I just installed it - lol! Thanks for the info. Any idea of where you can buy a new brass float?
I don't know where the best place is to buy one....but if you can drain it dry, it only needs a good soldering to repair it.

Maybe try Spectre tanks, RockAuto or Mega Parts
 
The reproductions do that, actually - both of the ones I've had only read half full when I've had gas
so full in the tank that it was climbing the filler neck.

I repeat, for the thousandth time - nobody makes a good reproduction sending unit for late 60's
b-bodies.
 
Right now I've dropped the tank, put in a brand new sending unit that tested out great out of the car, (it was completely wired and with a good chassis ground, etc.), tested the voltage limiter, tested the gauge itself, tested all the wiring, tested things that didn't even need testing, and everything worked perfect. I put back 9 gal. of gas that I had removed from the tank and I was cheering that the gauge read 1/2 tank! Took the car to the gas station to fill it up, and guess what? It stayed at 1/2 tank. The original sending unit that I removed only ever read 1/2 tank.
The only thing left is the possibility that the brass float was leaking, the brand new one is leaking, and both leak exactly the same amount. I just bought a new float from Classic (pn# 479312 - 10 bucks) for the car to see if all these floats leak the same. So far I have tested the original float and the new one from Classic under water for a week and neither took in any water. So this will be #3 once I suck all the gas out again, drop the tank again...yada, yada, yada. How about we just stick a chunk of foam in there, but something tells me it's not the float. I don't know...I should be playing golf.
 
I don't think the floats are leaking. I have had the same issues and just straighten out the bend in the float arm. This causes the pivot point to go up higher on the resistor. Usually takes a few trial and errors. You just want to be certain that when the gauge reads empty that there is a bit of gas over the pickup tube in the tank so you know when it is close to "E", you better be filling up. I also first bend the 3/8" tube a bit so the sock is resting on the bottom of the tank.
 
The reproductions do that, actually - both of the ones I've had only read half full when I've had gas
so full in the tank that it was climbing the filler neck.

I repeat, for the thousandth time - nobody makes a good reproduction sending unit for late 60's
b-bodies.
I used an original sending unit from a b body - it is not a reproduction. In addition, I used a nos lock ring as well.

So my sending unit is original, working, and no leaks. Just have the gauge issue.
 
Another easy thing you can do is loosen the wires on the gauge clean them up and tighten back up. This fixed an intermittent problem I was having.
 
Good morning gang.
I bought a new gauge from Charger Specialties and it never reads correctly. They have a completely different Ohms scale than the sending unit. Most sending units will read the proper Ohms, 0 or near o at full and 73 or near 73 at empty. Attach the sending unit to the sending wire "outside the tank" and ground the sending unit. Move it from empty to full and have someone watch the gauge. That will help you know how to bend or to add a resistor in the line. I have tried three sending units, all the same results. in my case, it is definitely the gauge from Charger Specialties. Nice guy, but his stuff does not work as OEM. Same problem with the tach that I bought from him.
69 GTX convertible
!
 
Good morning gang.
I bought a new gauge from Charger Specialties and it never reads correctly. They have a completely different Ohms scale than the sending unit. Most sending units will read the proper Ohms, 0 or near o at full and 73 or near 73 at empty. Attach the sending unit to the sending wire "outside the tank" and ground the sending unit. Move it from empty to full and have someone watch the gauge. That will help you know how to bend or to add a resistor in the line. I have tried three sending units, all the same results. in my case, it is definitely the gauge from Charger Specialties. Nice guy, but his stuff does not work as OEM. Same problem with the tach that I bought from him.
69 GTX convertible
!
I pulled the sender out of the Road Runner. Grounded it hooked up the sender wire and lifted the float till it stopped the gauge read full. I lowered it to half way and the gauge read half tank. Same goes with empty. I put the sender back in the car and blamo back to not reading correctly. So either the Range of the float is hindered or the rheostat is fked up from the factory. Outside of the tank reads fine. In the tank another story.
 
The float arm may need to be bent so the float is right at the bottom of the tank when empty?
 
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