Packard Forum Index » Post-War (1946-54)

My 51 model 200 gas gauge shows full when I first fill the tank. It drops a little as I start to use fuel to about 7/8 on the gauge, then it just drops to zero from there. I am thinking that it is the sender unit, and not the gauge. I will be pulling the tank for a flush and seal next week. Any ideas on how to test the sender?

Here is a photo of the sender internals. The resistance wire is supported by a phenolic strip bent to a curve which follows the wiper arc so as to provide equal pressure thruout the travel range as the two parts slide against each other. The wiper contact is a small smooth "button" on the end of a very thin and flexible strip of copper or bronze. It is possible some corrosion or oxidation has reduced the conductivity of the wire at the spot where the gauge stops registering. That can happen if the car sat for a long period with the wiper at that precise spot but the more likely is the phenolic has distorted from heat and age and the wiper is losing good contact where the gauge fails.

To test the sender connect an ohmmeter between the terminal and the support flange. With the float at the empty position you should read somewhere around 70-75 ohms. As you move the float toward the full position the meter reading should move VERY SMOOTHLY from the approx 75 ohms to approximately 10 ohms when the float is at completely full. If the meter reading suddenly changes and makes a big jump or goes completely open the wiper and resistance wire have lost a good connection. It could be from warping of the phenolic or oxidation.

The resistance wire is very delicate so be careful if you work inside. Don't use anything with much pressure to push against the wire. You may have some luck with contact cleaner but the phenolic is old and some cleaners are not safe to use with old phenolics. If the strip is already warped I doubt you will be able to do much and may even make the problem worse..

Attach file:

---

  (75.08 KB)

HH56 thank you for the photo and detailed description. Sounds like if electrical spray cleaner won't work that's it. Steel wool would be too much for the resister plate. This car was rebuilt about 35'years ago, and had around 700 miles on it since then. So the sitting in one spot for the wiper makes sense. Anyway I am having fun going trough the systems and making improvements. I can see the effect of each thing that I do. One thing about the Packard is unlike a modern auto, it was make to be serviced, and repaired. Any advice for a sender rebuilder? Tucsan Auto seems to have a decent price for this, or should I go down the 56 T-bird sender route that I have read about on the forum?

Kanter advertises repro senders for 51-4 at $95 so I don't know if a rebuilt would be any less. I haven't priced them. Some of the Ford repro senders are slightly less but as a few have found there are a couple of Ford varieties with different arm length and configurations and have gotten the wrong one.

When you get the sender out I would be very interested in the length or swing measurement of the 51 float arm. IIRC, it was mentioned in the last few weeks that there was a slight difference in senders or arm length and that was one of the reasons the reproduction tanks Kanter had made was not mentioned for 51s. The ohm range is the same so the length or the arm must be the main difference.

You might be able to take a cotton swab or similar and dampen it with the contact cleaner to gently wipe the resistance wire. I would go side to side so you are pushing from edge to edge with the phenolic and not go lengthwise with the arc where you could possibly push the wires together. As long as the phenolic isn't soaked it should hold up to gentle wiping. If the phenolic is not warped that might restore decent long term functionality but I wouldn't bet a lot on it.

Ok I will let your know what the arm length is when I get the sender out. It may take a week before I get to it. Is there anything I should know about disassembling the sender? Is it held together with screws, or is it a press fit of some kind?

It should have an O ring or sometimes a cork gasket in a recess on the tank. That sits under the sender flange. The sender assy is held on the tank by a ring with sloped ramps which usually takes a quarter to third of a turn to push and lock the sender tightly against the O ring.

HH56, I have removed and measured the fuel sender. The length of the swing arm from the pivot to the side of the float is 6" in a straight line. If you measure to the curve in the float arm it works out to about 6.5". The drop length of the swing arm is 5.25". My unit seems to have a warped phenolic strip. The wiper is just short of touching, then as it moves it increases pressure until it wants to stick on the back swing. I have opted for the repo unit from Kanter for $94 plus shipping. I really had to think about buying a rebuild from Tucsan Packard as it would have been nice to have one with Packard stamped on the flange but they run $125 plus core charges. My tank has been cleaned and sealed so hopefully no more,rust issues. I will let you know if this fixes the fuel gauge read when it's back in the car.

Just to update, I installed the repo fuel sender from Kanter. Seem to work fine, and is made from stainless steel.