39 ford deluxe

[jstrez5]

I am not getting a right reading from my gas tank where should i start looking for this problem can anyone help in this matter? thank you Jim S.

[Kube]

Originally Posted by jstrez5

I am not getting a right reading from my gas tank where should i start looking for this problem can anyone help in this matter? thank you Jim S.

Typically it is the sending unit in the tank. I'd suggest removing that first and foremost.
Check the float for buoyancy. Often times they crack and fill with fuel. If the float is good, check the sending unit itself.
Hopefully TomO sees this thread and weighs in as to how to check the tank unit. He's quite sharp on the electrical stuff. TomO?

[rotorwrench]

If yours is still an OEM King Seeley system, then you can actually take the cover cap off the sending unit and inspect the little bi-metalic strips and the tiny set of points that make the system work. There are other threads on this forum that describe ways to test the gauges. I think a certain value of resistor set in the circuit to bypass the sender will give a good test for proper indication.

If the old KS sender has been replaced with a modern rheostat type sender then the system will never give an accurate indication through the whole rang of operation. The KS system is current based and the later model systems are resistance based so they are incompatible in the rages that they work in.

[19Fordy]

rotorwrench is correct. Here's what sending unit looks like inside. Make an index mark on the cover and the case before taking apart. Use a flat blade screw driver or a conventional brake adjusting tool to gently pry off the cover. You can adjust the unit by turning the little star wheel with a tiny flat blade screw driver, BUT scratch a locating mark on the star wheel and the housing so you know where it was originally. Move star wheel only a tiny, tiny amount at a time.

[19Fordy]

Here's the rest of the story. Shown below is a 49-51 Merc unit but it operates the same as the 1940 unit. I think it's also the same as 1939. Be very careful not to damage the thin wires or carbon resistor?. Sanding the points with 600 grit wet dry emery paper may help. Try that first. Be gentle and be very patient. I have always wondered what that black carbon component really is and what it does. You will see it is color coded. Let us know if you can decode it and find answers to those questions. I think there must be a way to replicate this sending unit. Morris Gauge restores them. Here's what HAMB says:
http://www.jalopyjournal.com/forum/t...g-unit.796304/
and
http://www.jalopyjournal.com/forum/t...g-unit.730016/

[rotorwrench]

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Condition of the circuit wiring and ground path are also concerns for these old cars. Many times there is nothing wrong with the components that a good cleaning won't fix. New floats are available in repro but that's about it.

[adileo]

Originally Posted by Kube

Typically it is the sending unit in the tank. I'd suggest removing that first and foremost.
Check the float for buoyancy. Often times they crack and fill with fuel. If the float is good, check the sending unit itself.
Hopefully TomO sees this thread and weighs in as to how to check the tank unit. He's quite sharp on the electrical stuff. TomO?

Kube is right. On My 39 deluxe the cork was soaked and not floating. I bought drake after market and it didn't work. I cut the bar and float ball off the drake unit, had a friend weld it on old sending unit and presto - works great!

[jstrez5]

thanks for all your help guys. The weather here in PA. is a little chilly as soon as it warms up i will be working on the gas tank will let you all know when the tank is fixed and what the problem was thanks again. JIM S.

[britman]

My 39 deluxe requires a few minutes of "at speed' driving to come up to correct reading. If I check the gauge by just turning on the key I get nothing. The reasons have been explained on the FB having to do with the construction of the system--sending unit and gauge.

[adileo]

Originally Posted by britman

My 39 deluxe requires a few minutes of "at speed' driving to come up to correct reading. If I check the gauge by just turning on the key I get nothing. The reasons have been explained on the FB having to do with the construction of the system--sending unit and gauge.

That's odd. My stock 39 gas gauge moves as soon has I turn power on.

[JSeery]

I would guess there is some corrosion or a loose connection somewhere and it takes it a while to overcome it.

[TJ]

Originally Posted by britman

My 39 deluxe requires a few minutes of "at speed' driving to come up to correct reading. If I check the gauge by just turning on the key I get nothing. The reasons have been explained on the FB having to do with the construction of the system--sending unit and gauge.

Put an extra ground wire on one of the screws and run the wire to a clean ground on the frame. Looks to me like a grounding problem.

[ford nut]

9 times out of 10, ground problem.