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Old 09-02-2019, 08:16 AM   #1
randy993
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Default What OHM's reading sender for fuel tank

Hello all,
What is the correct ohms range for the sender in the tank to operate the factory dash gage?
Thanks in advance,
Randy
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Old 09-02-2019, 08:54 AM   #2
Jack E/NJ
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Default Re: What OHM's reading sender for fuel tank

There is no correct ohm range as the sending unit depends on the pulse rate of opening/closing points. https://www.fordbarn.com/forum/showp...4&postcount=12


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Old 09-02-2019, 09:12 AM   #3
19Fordy
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Default Re: What OHM's reading sender for fuel tank

Do a search on GAS TANK SENDING UNIT and tons of info will pop up. As you read through all of it you will gain a good understanding of how the sending unit and gauge work together and how to repair the sending unit.The most common failure is due to gasolene inside the float. Pretty interesting
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Old 09-02-2019, 10:33 AM   #4
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Default Re: What OHM's reading sender for fuel tank

When I replaced my tank I installed an aftermarket sending unit. At the time there were several to choose from that varied in OHM range. I went with "ORG - Early Ford & Mopar - 73-10 Ohms" . I got a voltage reducer and hooked up the guage. I checked it first by grounding it and it went straight to full so I believe that the guage is working properly. When I hooked up the sender wire it also went to full, just slower. My tank on my truck should be close to full so I'll just have to drive it some and see how it reads. I believe that i adjusted it correctly when I installed it.
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Old 09-02-2019, 11:54 AM   #5
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Default Re: What OHM's reading sender for fuel tank

Quote:
Originally Posted by randy993 View Post
When I replaced my tank I installed an aftermarket sending unit. At the time there were several to choose from that varied in OHM range. I went with "ORG - Early Ford & Mopar - 73-10 Ohms" . I got a voltage reducer and hooked up the guage. I checked it first by grounding it and it went straight to full so I believe that the guage is working properly. When I hooked up the sender wire it also went to full, just slower. My tank on my truck should be close to full so I'll just have to drive it some and see how it reads. I believe that i adjusted it correctly when I installed it.
The OEM gauges do not operate on an OHMs principle. Therefore an after market sending unit that operates on the OHMs principle will not work accurately with your OEM gauge. In order to use your OEM gauge you will need to install a "matching" King Sealy sending unit that Ford used.

To get accurate data, remove the gas tank sending unit when youR gauge registers FULL, 3/4, 1/2 1/4 and E and measure the depth of the remaining gas in your tank so that you can calculate how much gas is still in the tank at each reading.

For instance, when you measure the depth of the gas in tank when the tank is full you might find it's 9 inches deep with the 14 gallon tank.

Then when the gauge reads 3/4, again remove the sending unit and measure the depth of the gas in the tank. Let's say that measurement is 7 inches on your ruler. Then use the following ratio to find out if the amount of gas remaining in the tank is really 3/4 of the tank's 14 gal. full capacity.

9/14 =7/X X=10.8 gal. actually LEFT in the tank.

Three quarters of 14 is 10.5 gal. So your 10.8 gal. finding is pretty close.

Follow that same procedure at each of the the markers on your gauge to verify the sending unit is providing accurate info. to your gauge.

Pay special attention to the reading when your tank measurement is close to empty.

This process takes a while depending on how frequently you drive you car but, it's worth the time spent.

Last edited by 19Fordy; 09-02-2019 at 01:35 PM.
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Old 09-02-2019, 12:06 PM   #6
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Default Re: What OHM's reading sender for fuel tank

It is also possible to adapt the gas tank sending unit from another year Ford as long as it is a King Sealy unit. I used one like this in my 40 Ford after making a few adjustments. OEM gas tank sending units are getting very hard to find and are not cheap.
https://www.ebay.com/itm/NOS-OEM-For...cAAOSwpoxdVxoV

Last edited by 19Fordy; 09-02-2019 at 01:38 PM.
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Old 09-02-2019, 04:32 PM   #7
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Default Re: What OHM's reading sender for fuel tank

There is one advantage to using a mismatched aftermarket sender; it will probably always show the tank as full. That's a good thing (until you run out of gas).
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Old 09-02-2019, 08:41 PM   #8
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Default Re: What OHM's reading sender for fuel tank

Humorous comment there, Tubman Actually, I calibrated my sender with a series resistor to be accurate when the gauge reads nearly "E". That way I know to gas up.
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Old 09-02-2019, 10:23 PM   #9
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Default Re: What OHM's reading sender for fuel tank

In my '41 I used a 73-10 ohm sender from Yogi's and a stock gauge with a V reducer from Ron Francis. E was empty and I mean empty, would take almost 17 gal. Read full after about 17 gals. Close enough for me!
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Old 09-03-2019, 09:57 AM   #10
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Default Re: What OHM's reading sender for fuel tank

Quote:
Actually, I calibrated my sender with a series resistor to be accurate when the gauge reads nearly "E". That way I know to gas up.
That's what I did too. I found 7 ohms to work with my particular after market sender and float arm adjustment. (using what I had on hand, three 22 ohm resistors in parallel) Gauge needle will now get down to the E mark, and hits that mark with about 1 gallon in the tank.
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Old 09-03-2019, 10:38 AM   #11
19Fordy
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Default Re: What OHM's reading sender for fuel tank

I can't argue with success. Glad some folks were able to get good results with aftermarket sending units. Well done.
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Old 09-03-2019, 12:48 PM   #12
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Default Re: What OHM's reading sender for fuel tank

Quote:
Originally Posted by fordor41 View Post
In my '41 I used a 73-10 ohm sender from Yogi's and a stock gauge with a V reducer from Ron Francis. E was empty and I mean empty, would take almost 17 gal. Read full after about 17 gals. Close enough for me!
So there may be a chance that this will work for me. I know my tank is full so I need to drive it some. Going to the coast for a week as soon as the hurricane clears out. I'll drive it when I get back and see if it'll move. Thanks for the input.
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Old 09-03-2019, 12:58 PM   #13
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Default Re: What OHM's reading sender for fuel tank

[quote=randy993;1795103]so there may be a chance that this will work for me. I know my tank is full so i need to drive it some. Going to the coast for a week as soon as the hurricane clears out. I'll drive it when i get back and see if it'll move. Thanks for the input

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Old 09-03-2019, 04:30 PM   #14
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Default Re: What OHM's reading sender for fuel tank

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Originally Posted by randy993 View Post
So there may be a chance that this will work for me. I know my tank is full so I need to drive it some. Going to the coast for a week as soon as the hurricane clears out. I'll drive it when I get back and see if it'll move. Thanks for the input.
Some folks claim to get them to somewhat work and other claim not close at all. So, take your pick, LOL. It is a different setup from the original, resistance versus a set of points pulsing the current. If you can get the current flows to match the different sender arm positions it should work ok, but the trick is getting them to match! Ford obviously thought the points were the way to go and not the resistance units as they used the same basic current-pulse setup into the 70s or 80s. (1985 was the last year I believe).

Last edited by JSeery; 09-03-2019 at 05:22 PM.
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