'63 Fuel gauge not working

[hanko mechanico]

Tom, I looked up that gauge from Dennis Carpenter you mentioned and it's exactly what I have. My float rod is only 5 inches long so was probably shortened. My sending unit is most likely defective but probably worked at one time before I owned the car. You also said you have a sending unit for sale. Would it work in my 57? Thanks

[hanko mechanico]

Tom, I looked up that gauge from Dennis Carpenter you mentioned and it's exactly what I have. My float rod is only 5 inches long so was probably shortened. My sending unit is most likely defective but probably worked at one time before I owned the car. You also said you have a sending unit for sale. Would it work in my 57? Thanks

[tomo]

After further research, I don't believe that you could make the one that I have work in your Lincoln. There appears to be differences in the windings between the 6 volt units and the 12 volt units. The 1936-1955 sending unit from Dennis Carpenter will not give you a full reading and the empty reading would be around half tank.

The Dennis Carpenter unit for the 1957 Ford has readings of 9-79 ohms and the original Lincoln was 2-67 ohms according to this post: https://www.thelincolnforum.net/phpbb3/ ... hp?t=37895

You could use this unit by switching the mounting plate for the one that you have with the mounting plate of the 57 Ford. The unit may not give you a full reading, but it will be much closer than you have now.

https://www.dennis-carpenter.com/cars/f ... it-12-volt

[TonyC]

Sorry if this looks like a hijack, but it is related to the topic. The recent discussion triggered a thought that never occurred to me before.

On mine, the sending unit causes the gauge to read lower than the actual supply. My sending unit is a repro unit I got 5 years ago, and it's been this way since I installed it. If I were to bend the float rod downward a bit, would that possibly make the gauge behave more accurately?

---Tony

[frasern]

Probably not, if the float hits the tank bottom, it will read higher, if bent up, it will also read high. The float needs to almost touch bottom, but not quite, only way to adjust it is with a borescope, or some way to visually access it.
When I fabricated a pickup for my truck, I had a scrap tank that I cut open, to see exactly where the float sat top and bottom, I then adjusted the length and swing to the best fit. Disclaimer; do not cut open a gas tank, it will catch fire!

[Lee]

Tony, I'm going to give that idea better chances than Fraser. If you bend the arm down, the resistance wiper should then ride higher, in a lower resistance area. I think.

If you run into a geometry problem like Fraser mentions, you can shorten or lengthen the rod as required.

[TonyC]

Thank you for the input. It occurred to me that I never compared the respective angles of the float rods in detail between the old and new senders. I just looked at their general similarities and hoped for the best where the low-fuel light was concerned. That's not an immediate concern for me to check, but I will try that when I can again access my sending unit.

---Tony

[frasern]

Every domestic vehicle I have ever driven reads empty with a couple of gallons left, but some are worse than others. The rheostat will not go any lower than it's stop, the float should be just above the tank floor at that point. It is possible for that arm to have been bent a little during shipping or installation, but more likely the unit is just a tad off in resistance. If the issue is the light, I believe that is unrelated to the float, and it may be possible to tweak it's position, but I would have to have a closer look.

[Lee]

For my ‘62, I have only run out of gas once, and that was on a pretty deserted stretch of 66 in Arizona. Anyway, I suspected I was about to run out, so I made careful note of when the needle and the E mark lined up exactly. 12 miles later I was on the side of the road with my thumb out, so mine has less than a gallon reserve.

I was eventually picked up by a 20-something local in a ‘59 El Camino. You can’t make this stuff up.

[frasern]

Hank, I went and had a look today, at the closer car, it is a '57 Capri 4 dr. but It is junk, the hood is surprisingly straight, but every other part is smashed and rusted, interior is out, some parts still inside, but every window is broken, so nothing of value in there It still has an engine, but I couldn't open the hood.
The fuel tank is still in, but that sender may be good or bad. Probably not worth the drive, but next time I see the guy, I will ask about it, he was out seeding today.

[MrVee]

Dan Sawarc wrote: "You can short the pins which will drive the gage to fill without pulling the sender (just not for long)". I'm curious what the "not for long" is a warning about. My 64' gauge will read "full" when directly grounded at the sender plug. However, it displays "empty" whether it is unplugged or hooked up to the sender (which was replaced). The sender is reading 62 ohms and probably has between 1/2 and 3/4 of a tank of gas.

I'm not sure what else to check... the wiring proves good as I would believe the gauge does since it will read full grounded. I had probably left it conceded to ground for 5 or ten minutes while testing and wondered if I might have caused some other problem.

Thanks for any advice.

[Lee]

Dan Sawarc wrote: "You can short the pins which will drive the gage to fill without pulling the sender (just not for long)". I'm curious what the "not for long" is a warning about. My 64' gauge will read "full" when directly grounded at the sender plug. However, it displays "empty" whether it is unplugged or hooked up to the sender (which was replaced). The sender is reading 62 ohms and probably has between 1/2 and 3/4 of a tank of gas.

I'm not sure what else to check... the wiring proves good as I would believe the gauge does since it will read full grounded. I had probably left it conceded to ground for 5 or ten minutes while testing and wondered if I might have caused some other problem.

Thanks for any advice.

I think the issue is that "Full" at the sender isn't 0 ohms, its approximately 10 ohms, and by grounding it, you are probably pegging the meter. It might survive that treatment, and it might not.

If you are reading 62 ohms at your sender, are you testing it from the sender terminal to the gas tank, or sender unit to a frame member?. My point is that if the gas tank isn't well grounded to the rest of the body, that could be your problem.