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John ED Renstrom
04-26-2017, 11:06 PM
the fuel gauge in the 67 has been stuck on 1/4 since we got the car. so we are up to there. checked to be sure that we had power both side of the superior splice just under the front seat and traced the wire back to were they came out of the wheel well in back. we have power there. made sure we had a good ground and there was power to the sending unit. so the next step is to check the gauge. took the wire off the sending unit and the gauge goes to full. ground the wire out and it goes to empty. so the gauge is working as it should.

it has to be the sending unit is stuck. did the drain and drop the tank and it was as I thought. all most. the float was gone ate up in the standing still for a long long time. we have another sending unit but first we will see if this one works. I have a couple poly floats and a couple brass ones if it does. I did find the solder ring when we flushed the tank. but not any other hint of it.

Walter Suiter
04-27-2017, 02:47 AM
There is a dirty trick for determining sender problems from gauge problems.

A 250 or 300 ohm rheostat can be substituted for the sender resistor, and will occasionally save you dropping the tank.

John ED Renstrom
04-27-2017, 12:06 PM
The simple open wire then grounded wire can be done with out dropping the tank. Which is the Factory approved way to testing the gauge. As in this case I could get the gauge to read on the high end and the low end it tested good. The problem was in the sending unit.the 50 year old tank needed to have the loose drug removed anyway. And we have gotten that done
Today I will see if we can clean out the build up in the sending unit so that the arm will swing free. If we can get that done I hand a new float to put on the arm.

Yes I could send it off to get fixed our just swap out with the new one I have. But we're is the fun in that. Time is not money in this case. We can play around a little.;)

Walter Suiter
04-27-2017, 12:28 PM
Kroil. Preferably with teflon.

Probably a good idea to check the resistor with an ohm meter before investing time in the workings.

John ED Renstrom
04-27-2017, 11:40 PM
will it was a fun day. all we could get the original unit to do after it had been out and moved around was read a complete open. so we tore it apart so see how it looked in there. what wasn't rusty was badly corroded. played around a little and as expected it pretty much fell apart just looking at it. if you ever wondered what one looks like on the inside here it is and the inner workings. I did find the stamping for the ohms it is rated at. that helps. one week link is the way they jam the resisters agents the stop punched into the shell. that is the way it completes the circuit. what we ended up ere is lose of contact at the power peg the brass has corroded to were power was not getting to the resisters.

John ED Renstrom
04-27-2017, 11:43 PM
darn forgot the up load button again here are the pictures

John ED Renstrom
04-28-2017, 11:46 AM
Now we had this discussion on a different thread. Paul had pointed out the error in my thinking. That GM had changed the value of there sending unites in 65. 65 and up are the 90 ohm units. So I need to correct any statements I have mad in regard to this.

57-58 CC cars use the standard 57 fuel tank and sending unit. The 59-68 CC cars use the 58 standard tank and the 30 ohm 57 sending up it up threw the 64 modal year. After that the sending unit is a 90 ohm unit. Same size and shape. But the different resister value. The 69-70 use this same sending unit. But there tank has a return line in the AC cars.

So Paul was right I was not. Sorry if my confusion caused any trouble for anyone. Any one have any leads on a 90 ohm sending unit? The 30 ones will read full just under the 1/2 way mark on the Gage and drop to empty from there. Still better them none but not handy.

Peter Grave
04-28-2017, 12:23 PM
You can add a resister in line to compensate for 30 vs. 90. I think a 60 ohm will do it. Let me check with one of my technoid friends and will post more later.

John ED Renstrom
04-28-2017, 11:25 PM
it might be possible but I just broke down and got one of the doesn't fit anything universality units. it took a little playing but we got the arm to swing the same as the original and put it in. it's the only 5 hole 90 ohm sending units out there I could find. I just hoping that when I go it and tighten down the set screw I did not make a mistake buy not putting a drop of brass on it. it read higher then it did so it might be working . to laze to run down and get 5 gal to see if it comes up. sloppy snow out there this morning.

here is what we did to make it work. at least on this car with the bumper off we can work on it with out dropping the tank.

Walter Suiter
04-29-2017, 03:03 AM
Is that unit from Tanks Inc?

John ED Renstrom
04-29-2017, 11:52 AM
Who can say who built it it was off the shelf at the local parts store. No name on the box none on the sender