grounding bob drake fuel sending unit

[allenmichael]

1936, still 6 volt, new fuel tank and sending unit. Continuity exists between tank and gauge. will grounding sending unit to metal floor of car be enough ( which I did) however unit still not reading. Should i move it to a heavier gauge ground source?

[Kube]

Originally Posted by allenmichael

1936, still 6 volt, new fuel tank and sending unit. Continuity exists between tank and gauge. will grounding sending unit to metal floor of car be enough ( which I did) however unit still not reading. Should i move it to a heavier gauge ground source?

Grounding to a clean spot on the floor is more than adequate.
You most likely realize that the Drake units are "iffy" at best.

[JayChicago]

Agree.

Could be bad sending unit, or a bad gauge.

To test the gauge: with a helper watching the gauge, switch on, briefly touch the end of sender wire directly to ground. With zero resistance there, needle should move towards full.
If it does, assume gauge is good, must be bad sender.

[allenmichael]

Jay, on which end of the circut of the sender wire do you directly touch to ground? Is it leave sender wire connect to sender and then touch gauge end to a ground? or jump from ground at sender unit to sending terminal? hope this makes sense.
Mike

[JayChicago]

Disconnect wire from sender terminal, touch that wire to ground.

Or yes, as you said, leave connected to sender terminal, rig a jumper wire from sender terminal to ground. Will give same result.

[Karl Wescott]

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Original gauge... Likely a King-Seely system. I do not really understand it but what I do suggests the sender sends pulses to the gauge and bumps the indicator, the more pulses the higher the indicator goes (don't ask me how).


Aftermarket sender... (used by most aftermarket gauges) senders use a rheostat (variable resistor) to vary voltage and the gauges is basically a voltmeter.


King-Seely gauges will ocassionally, but not always kinda work with the aftermarket sender. Empty could show as empty, Full could show as full, but anything between will be random to that gauge and sender.


There are some great threads on the subject with 747 explanations of how the King-Seely system works. Search for them. (747 jet... way over my head).

[JayChicago]

Yes, he has a modern sender which will never produce accurate readings on an original K-S gauge. But it should show something.
My understanding is he is getting no needle movement at the gauge. Probably a bad sender. Probably the tiny rheostat coil in the sender is broken open.

[allenmichael]

Thank you Jay, that is exactly what I needed to know. Now off to see what is what!
Mike

[kurt v]

I don't know if i read correctly or not but by using a sender up into the 50's (still 6 volt) will work with the orig gauge, but i may be wrong.

[glennpm]

Originally Posted by Karl Wescott

Original gauge... Likely a King-Seely system. I do not really understand it but what I do suggests the sender sends pulses to the gauge and bumps the indicator, the more pulses the higher the indicator goes (don't ask me how).

Jseery gave us an explanation.

https://www.fordbarn.com/forum/showthread.php?t=165773

[1942deluxe]

On my 46 the dash gauge wasn't registering after installing a new sender. Checked the connection at the tank and it was loose. Added a small washer and it worked.

[Automotive Stud]

I had the float sink on a new Drake sender. Put my original float on it, which was bigger and I had to bend the arm, and it works again. Just because it's new doesn't mean it's good.

[rotorwrench]

The big unknown is what Ohm range would give a King Seeley quantity indicator a full sweep from E to F. The current pulse system didn't have the same range due to the way it controlled power at the indicator. The indicator function is the same theory but current control doesn't involve any rheostat. The float arm movement affected the movement of the sender breaker points on the bi-metallic regulator switch arm. K-S used a resistance wire spool and a carbon resistor to calibrate the system circuit. If you chuck the original sender and convert it to rheostat, the Ohm difference between E and F on the indicator need to match up with the resistance range that gets it there.

Ohm controlled quantity systems use specific Ohm values and from research, most are limited to three or four different values between different manufacturers. They should test a K-S indicator with a good variable resistor test aperatus to find what range effects it and manufacturer one that works. I think they just got one of the off the shelf units that's close and called it good. I'd be surprised if they care whether it works or not.

[34fordy]

I have found, after too many length adjustments for my Drake sender, it reads full for a long period of driving and then down to 1/4 full quite quickly. That is when I head to the gas station. Today the gauge indicated about 7/8 full. I add 9.3 gallons. The worst thing is a Ford sender will not fit in the hole in the Drake tank. Had to buy a Drake sender. Purposely ??

[rotorwrench]

Yep, the bungs are different. Some can use an adapter but I don't know which ones.

[JayChicago]

Originally Posted by rotorwrench

They should test a K-S indicator with a good variable resistor test aperatus to find what range effects it and manufacturer one that works.

Wouldn't that be nice. Probably never see it happen.

[34fordy]

Originally Posted by JayChicago

Wouldn't that be nice. Probably never see it happen.

No matter how important these issues are to all of us we have moved into the

"WORLD of IRRELEVANCE" !