Weird fuel gauge reading issue

I siphoned it and yanked it. Not too bad. Took about 20 minutes. I pulled the sending unit. It’s bad.

JIM said:

I pulled the sending unit. It’s bad.

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I'm guessing you took a meter to it to see if it swung from 0 ohms to about 90 ohms when the float arm is manually moved through it full travel ?.

If you used the factory connection points and depending on the design of the sender is on some originals there is the push on connector on the topside of the sender and this is to an insulated through pin and then on the underside a flat piece of metal with a hole in the end has the end of the through pin going through it and then secured with a push on locking washer. I have seen sometimes a poor connection between this pin and the flat metal strip.

I then have seen the other end of this flat strip then riveted to the housing that internally contains the wraps of wires to get the different resistance values. Sometimes this riveted connection is not good.

The last thing I've seen is sometime not enough tension on the wiper arms contact to the windings of wire inside the sender housing. A little rebending to get more tension sometimes gets things working as well as some contact cleaner if the wraps of wire have corrosion on them and/or the wiper arms button.

Sometimes there is a break in the windings and for that a whole sending unit replacement is the way to go.

Jim

Jim, thanks for the follow up. Yea, I have the original AC Delco unit and it has the strap leading to the push through pin on the underside. I checked right on the strap itself of the float and it was open. After moving it back and forth a few times, I got a reading out of it but it was not correct. It read 25 ohms at the bottom and 135 ohms at the top. It was intermittent as well. Would occasionally go to the k-ohm scale and then open again. I thought about contact cleaner but since it’s inside the tank, I was not going to take a chance on it failing again a month later. I ordered a Dorman replacement. Should be here today. $33 on Amazon.
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