Fuel Sending Unit Idea

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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dpcd67
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Fuel Sending Unit Idea

Post by dpcd67 » Thu Jun 23, 2022 6:53 am

Ok, with all the discussion of fuel sending units, and associated issues, I thought of this: I know there are solid electronic sending units on the market, with no moving parts. Without considering originality; why can't I install one of those and avoid all the hassles of the float, resister windings, corrosion, etc? I have the same thing in two sump pumps in my house and they work great, replacing the old float types.
I see them in various lengths. And the OHM thing; I understand zero about. Why is this not the final solution? Again, forget original configuration for now.
So, you electrical experts, tell me if this will work. With a WW2 fuel guage.
Yves; Nuclear Genius; do some math or something and tell me about this.

I forgot the best part; these things are like $20.
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Re: Fuel Sending Unit Idea

Post by Chuck W. » Thu Jun 23, 2022 10:19 am

Back when I was trying to get the fuel gauge to work in my 1964 CJ3B, I purchased a KUS hall effect Fuel and Water sensor, 4" long. This is a 12 volt unit. I machined an adapter for the tank. It worked perfect, but I was unable to make a gauge fit in the original gauge cluster, and decided to go another route. It looked like this, only shorter.
Image

I still have the sending unit if you are interested. I'll never use it.

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Re: Fuel Sending Unit Idea

Post by dpcd67 » Thu Jun 23, 2022 1:30 pm

Yes just like that, only it will need to be longer than 4 inches. Will that work with a WW2 gauge? This is where I need the electrical guys who know what an Ohm is to chime in. Please don't tell me that Ohms is resistance and potential and volts, and definitely don't use the water in the dam analogy.
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Re: Fuel Sending Unit Idea

Post by Wolfman » Fri Jun 24, 2022 4:18 am

I doubt using the sending unit in your picture and an original gauge will work.
The unit in the picture has a lot of electronics inside. No moving parts in contact with each other.
The original was completely mechanical.
Simple enough ??
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Re: Fuel Sending Unit Idea

Post by YLG80 » Fri Jun 24, 2022 6:17 am

dpcd67 wrote:
Thu Jun 23, 2022 1:30 pm
Yes just like that, only it will need to be longer than 4 inches. Will that work with a WW2 gauge? This is where I need the electrical guys who know what an Ohm is to chime in. Please don't tell me that Ohms is resistance and potential and volts, and definitely don't use the water in the dam analogy.
No I never fill my fuel tank with water :)!

The hall effect sender is a nice solution when the tank has not an odd shape like the MB/GPW tanks.
Then, no hassle, you can buy a ready to use couple gauge/sender for example like this one from SW:
Stewart Warner 82303 Deluxe 2-116 Fuel Level Electric Gauge  Automotive.jpg
Unfortunately you would have problem with the MB/GPW tank.
The magnetic float of the Hall effect sensor would not have a vertical coarse, as needed.
And the sender could not reach the bottom of the fuel tank.

Fuel_Tank_Sender_Axis.jpg

A coaxial capacitive sender would be a better solution in that case, as there are no moving parts in that type of sender.
It can be positioned like that in the tank.

Fuel_Tank_Sender_Axis_Capacitive_sender.jpg

This is the principle of such a simple sender


capacitive sender.jpg


But an interface needs to be placed between the sender and the gauge to calculate a few fuel levels points in the odd shape tank and calibrate the system.
This can be done by a one time self learning operation in the processor interface, i.e a single PIC chip or an Arduino chip for example.
The interface drives also the gauge current and it can be adjusted to any gauge.

That device is simple, cheap and allows the use of the original gauges.
The interface is so small that it could be assembled directly on the sender on top of the tank.

That interface is used in France by collectors of vintage Alpine Renault sport cars.They also want to keep the original fuel gauge on the dashboard.

Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
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Re: Fuel Sending Unit Idea

Post by dpcd67 » Fri Jun 24, 2022 6:30 am

Yves comes through again! That is exactly what I wanted to know; will it work with a WW2 fuel guage and the answer is YES.
So, disregarding the two level thing for now; assume that it is straight up and down; the combination would be the WW2 gauge, and a 240-33 OHM electronic sender; is that right?
Wolf, thanks......
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Re: Fuel Sending Unit Idea

Post by YLG80 » Fri Jun 24, 2022 8:11 am

dpcd67 wrote:
Fri Jun 24, 2022 6:30 am
Yves comes through again! That is exactly what I wanted to know; will it work with a WW2 fuel gauge and the answer is YES.
The capacitive sender would indeed work with a WWII gauge providing that an interface is used.

The KUS sender would work with a WWII gauge IF the fuel tank has a simple shape similar to the CJ3B fuel tank.
That type of sender has to be vertical and it is not a hall effect sender.
It's a reed relays with a chain of resistors sender that is a very good choice to keep things simple.
Here is how it looks an works:

KUS_reed_gauge-1.png

The sender is powered via the level signal pin. The current flows through a chain of resistors. Each resistor in the chain is connected to a magnetic switch.
When the magnetic float is in front of the switch it closes the contact changing the sender ohm value.
When the magnetic float reaches the bottom of the sender, another switch is activated to produce a warning signal.

Not sure if the range 230-33 ohm will be OK with the original WWII fuel gauges.
KUS offers 0 to 190 ohms senders for the European market.
I guess that these European senders would work with the jeep fuel gauge without any change.
I have ordered one to make some tests. Sorry it will be a 0-190ohm sender as I'm located in Europe.
Yves
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Re: Fuel Sending Unit Idea

Post by dpcd67 » Fri Jun 24, 2022 5:24 pm

Awesome! We can easily get the 0-190 OHM European senders here; eBay is full of them. I don't know what a Hall effect is. But I envision a vertical sender and a flat fuel tank; not stepped like a WW2 in this case.
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Re: Fuel Sending Unit Idea

Post by Wolfman » Sun Jun 26, 2022 5:11 am

Be sure you know what you are buying, TJ. Apparently more than one type that looks similar.
The sending unit in Chuck's photo and Yves described the function of is not what I was referring to. Never saw one like this before, with the float.
As Yves described, the resistance in Chuck's unit changes by a magnet in the float, that slides up and down the tube with the fuel level, activating switches inside the tube to connect a series of resistors together to change the overall resistance to the gauge. A different approach to achieve the same function as an OEM sending unit. A mechanical/electronic set up.
Yes, this would work with an OEM gauge, as long as the resistance range was correct for the gauge.
What I was referring to is a sending unit that looks like the one in Chuck's picture, but no black float on the tube.
The tube is hollow with a small rod with insulators on it, inserted into the hollow tube. The rod is as long as the tube it is in. The insulators keep the rod from touching the tube wall.
The tube has a vent hole at the top and as the fuel level in the gas tank increases or decreases, the fuel level inside the tube matches the outside level. Current flows through the fuel between the rod & tube so when the tank is full, more fuel is in contact with the rod & tube, so there is more current flow between the rod & tube than when the fuel level is low. Electronics in the sending unit head & gauge detect the change in current flow and convert this to a gauge reading.
No moving parts. Completely electronic.
I have used this type of gauge & sending unit on several homebuilt aircraft, and it works great.
The gauge and sending unit are sold as a set and an OEM gauge will not work with this type of sending unit.
The tube & rod can be cut, as long as the tube length stays longer than a specified minimum length. There is an adjusting screw on the sending unit to adjust the sending unit for the shorter tube/rod length.
Note, either one of these gauges would have to be moved on the tank top so the tube was in the deepest part of the MB/GPW type tank for a proper reading.
Update: Amazon had listings for the type sending unit in Chuck's picture.
Checked with Aircraft Spruce and they listed Westach, Swift and Skysport capacitance units like i described.
Mike Wolford
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Re: Fuel Sending Unit Idea

Post by dpcd67 » Sun Jun 26, 2022 6:31 am

You build airplanes? Way cool. Not that I want to ride in an airplane. Might jump from one again.
Anyway, so, the black thing moves up and down? The ones I see in pictures, do not have that feature.
And the ones with the black float will work with WW2 gas gauges and the smooth ones won't? That is what I want to know. Again, disregard the two step jeep gas tank for now. Assume one level.
And the Ohms? 0-190 is the one to get?
You guys know about electricity; I will have to ask you about one wire alternators, but not now.

Ok, I found more of them on eBay; for $20.59. With the black float in various lengths. in 0-190, or 240-33 OHMS. Which will work with WW2 gauge? I think Yves said the 0-190 one.
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Re: Fuel Sending Unit Idea

Post by YLG80 » Sun Jun 26, 2022 9:17 am

What Mike has very well described is a capacitive sender unit.
You can even use a standard coaxial cable terminated by a weight connected to the inner conductor.
It works but the capacitance range between full and empty is rather narrow.
This is not the current that changes with the liquid level, but the capacitance which is used to change a Pulse Width Modulated signal, i.e PWM.
Gasoline has an almost infinite resistance, so the current between the tube and the rod would almost not change with the fluid level.
With water, that is another story and it works very well, although not very stable.
And do not forget to consider the electrolytic effect with a DC current through the sensor.

As Mike wrote, a capacitive sensor cannot work as is with our vintage military vehicles.
However, as usual the electronics, a microprocessor and a few lines of code are helping a lot. :wink:
It’s very cheap (about 10-15€) to make the interface between the capacitive sender and the vintage fuel gauge with an Arduino Nano processor.
No need for additional components, it uses the circuit as is.
An the sensor can be placed in any position providing that it goes down to the bottom of the tank.
Yves
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Re: Fuel Sending Unit Idea

Post by YLG80 » Sun Jun 26, 2022 9:20 am

dpcd67 wrote:
Sun Jun 26, 2022 6:31 am

And the Ohms? 0-190 is the one to get?
The 0-190 sender I’ve ordered has been shipped.
Not many nights to sleep before knowing how it works with an original GPW fuel gauge :wink: .
Yves
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Re: Fuel Sending Unit Idea

Post by dpcd67 » Sun Jun 26, 2022 10:06 am

Ok; good. And since your nights are our days, I won't be sleeping at all.
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Re: Fuel Sending Unit Idea

Post by YLG80 » Mon Jun 27, 2022 1:41 am

FYI, so that you will have a complete view on the different FLS systems, you have also the ultrasonic liquid level sensor.
That is a neat solution that I have used to monitor the rainwater level in my 10m³ underground rainwater tank.
Here is how it works. No moving parts

Ultrasonic.jpg

It works very well with my rainwater tank, but I 'm wondering how it would work with a moving fuel surface in a car.
By software we could smooth the measurement.
The very small device is very cheap to make, even with Bluetooth to ring your phone and inform you that your military vehicle will be very soon out of fuel :).
Yves
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Re: Fuel Sending Unit Idea

Post by Wolfman » Mon Jun 27, 2022 4:36 am

Welcome to the 21st century. The fuel tank sending unit sends a message to your cellphone that you are out of gas. Beam me up Scotty.
In the old days the engine sent the message. It quit running ! :lol:
First time I have seen an ultrasonic level gauge. More modern magic. The sending unit shoots a signal at the liquid's surface and measures the amount of time it takes the signal to reflect off the surface of the liquid and get back to a receiver on the sending unit. Then coverts the elapsed time it takes the sent signal to return to the sending unit into a level reading. ??? Distance measuring device. I have seen those.
No big deal on a one wire alternator. The electronic regulator is inside the alternator and gets the information it needs to control the charge rate from the big battery wire terminal.
Mike Wolford
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