The Great Fuel Gauge Debate

[Nelsen Motorsports]

Been a while since I have been able to put some elbow grease (and dollars) into the hot rod Studebaker, but here we go. Next project is removing my ATL NASCAR fuel cell because the bladder leaks and install a universal mid 60s Mustang fuel tank. The question has to do with the many options for fuel gauges...

I have a Stewart Warner gauge set in the Hawk dash and can get any ohm rated gauge and sending unit: 240/33, 73/10, or 0/90.

The price is the same regardless, both for the gauge and sending unit.
Stewart Warner seems to specialize in the 240/33 unit, but it shouldn't make a difference.

Does it matter which I choose?


Pic of the tank for those interested. It will bolt into the trunk floor and I will have no fender fill.


Thanks,
Alex Nelsen


Also, to the inspiring racer, I have some deeply discounted fuel cell parts.

[StudeRich]

If you have a original OEM Studebaker Hawk (Stewart Warner) Fuel Gauge, it only works correctly with a 33 to 240 OHM Sender.


I guess you would have to do some major work to the Float Arm Length to use a different depth tank than stock however.

What is that one, a 4 or 5 Gallon tank?

[Nelsen Motorsports]

If you have a original OEM Studebaker Hawk (Stewart Warner) Fuel Gauge, it only works correctly with a 33 to 240 OHM Sender.


I guess you would have to do some major work to the Float Arm Length to use a different depth tank than stock however.

What is that one, a 4 or 5 Gallon tank?

I'm actually quite impressed with the aftermarket today. That is a 16 gallon 1965-66 Mustang fuel tank with a cap where the inlet hose would go. The tank will effectively be my new trunk floor. I then get an aftermarket sending unit that is cut-to-fit and off I go.

These are pretty common for street rodders and especially people building classic trucks and wanting to move the tank out of the cab.

http://www.tanksinc.com/index.cfm/page/ptype=product/product_id=276/mode=prod/prd276.htm

These are the sending units that bolt in the tank.

The only thing I wish they offered was the 1970 Mustang size of 22 gallons with cap.

Pretty soon I will be able to say my car has Chrysler, GM, Ford, and Studebaker parts.

[junior]

There was an blurb in Hotrod magazine a while back...I think it was the 'we're going to fix it ' story...about a new style of fuel sender where the float surrounds a column...as it rises and falls it changes resistance. no touching parts to wear out, accurate, and no float arm to deal with...I thought it was really slick and figured next time my Stude one fails I would look at that option. Sorry, can't remember who makes it, maybe someone else can. Does your car still have those awesome headers on it? Cheers, Junior

[junior]

Went and dug through the Hotrod mag. piles...Aug 2016 is the issue, WEMA is the manufacturer, reed switches and not resistance...and float is good for over 50 million cycles. sounds cool to me. hope this helps. cheers, junior

http://wemausa.com/

Liquid Level Sensor
SSS Level Sensor
Reed Switch Level Sensors

Level measurements are done by series of hermetically sealed reed switches positioned inside the main shaft of the sensor. A float with built-in magnets then triggers the reed switch relays, generating a potential-free Reed Switchresistance with ohm value that increases or decreases according to the fluid level. Output is fully customizable, available as resistance, current, or voltage signals.

The advantage of reed switch type level sender over thick-film swing arm type level sender is the reed switch�s durability and reliability. Switches used in the reed switch level senders are able to perform over 50 million actuation cycles, more than 5 times that of thick-film resistors. Additionally in reed switch level senders the float is the only moving part of the sensor, thereby minimizing potential mechanical failures.

The standard level measurement resolutions on our level senders are approximately 0.5� (13mm). However, if your level measurement application requires finer resolution, customized senders with resolution as low as 0.18� (4.5mm) are available upon special request.

All sensors are fully insulated to protect against spark and voltage inside the tank.

[gordr]

There is a style of mud tank (for drilling rigs) level sensors which work that way. Long stainless steel column about an inch in diameter; spherical float ball with a sleeve running pole-to-pole that is a free slip fit on the column. Ball contains a magnet; column has a long string of reed switches and resistors. Higher the float gets, the more resistance gets switched out of the circuit. De Laval is the name of the design.

I believe ultrasonics have mostly supplanted them. Compact little device, sends a beam of ultrasound straight down; it bounces off the surface of the liquid in the tank, and transit time gives you the level. Just like radar. With modern microelectronics, you could probably build the whole works into a hockey-puck sized device that would bolt up to the standard sender hole in your tank, and have it programmable via a USB cable so that different shapes and depths of tank could be read accurately. And have it output a varying resistance that mimics the original sender, or whatever matches the gauge used.

Industrial sensors like the mud probes described above commonly work on a 4 - 20 milliamp current loop. Four milliamps returns a zero reading, and 20 returns a maximum reading, whatever the actual sensor is measuring. Source voltage is 24 volts, but available current is not much more than 20 milliamps. Such a design means that cable resistance on long cable runs is basically unimportant, and there is not enough current available from the source to make a spark that could ignite explosive vapors.