Automotive fuel level sender project

So i have a faulty fuel level system that constantly reports inaccurate fuel levels to my car's fuel gauge. The fuel level sender is integrated to the fuel pump which sits in the fuel tank. The fuel sender uses a variable resistance strip (0 to 200 ohms) where a float arm moves a contact pad across it. This is the source of its inaccuracy because not only does the pad and strip wear out quickly but is directly in contact to the gasoline which corrodes it. My project involves using a new float-less fuel level sender that many in the hotroad/racing and offroader community uses in their fuel cells. Unfortunately there is no product that matches my required resistance range 200hm=full fuel & 0.5 ohm= empty. In fact their values are the opposite. The closet one i could find is 30 ohm to 240 ohm. So my idea is to create a circuit and software that can translate these ranges that my fuel gauge can read correctly. I could use some advice and tips on how to go about this.

Do you have on in hand so you can test?

Is this just to replace the fuel sensor or the gauge as well?

New automotive dashboards read voltage from the level sender. You should be able to flesh out the voltage vs gauge reading pretty easily. The reset should be easy.

Depending on the year, the level sender is grounded at the ECU NOT back with the pump.

Remember, the Arduino AnalogWrite is actually a PWM and will need filtering to go to the vehicle ECU.

Basically, not an Arduino/ microcontroller topic. Unless there is some major non-linearity issue that requires the computing power of a microcontroller, this is something you do with an op-amp.

Now note that for this sort of thing where you need to drive significant (well,modest) current, a likely suitable op-amp is an LM386! :sunglasses:

Paul's suggestion is correct, you should use an Op-Amp, though you can probably get away with just a single PNP transistor to do the job. Fuel gauges are something in between a current-meter and a Voltage meter when used in an analog system. The current should be low enough to not make sparks, but the voltage across the sender should be low enough for that same reason.
I did a project where i hooked the sender of my LPG tank to the Fuel-gauge on the dashboard, using an Op-Amp to invert the signal (the LPG sender was inverted) and correct the bias. The LPG tank was a 5v System so that had to be dealt with.

Totally. Your suggestion of Op-Amp type is also very functional (Though i believe that type is considered obsolete by some, but i don't see any reason to not finish all of them that were already produced if they suit the application. That goes for all obsolete parts in my opinion btw)

The gasoline itself doesn't corrode it as far as i know, but the humidity does, and the gasoline dissolves any preserving agent on the variable resistance.

Which is all very funny as I have never had any problems with the fuel sender on any of my cars.

What sort of car would this be anyway? :face_with_raised_eyebrow:

I don't know about his, but i did have to replace one on Mazda econovan diesel once. It being right at the top of the tank, i had to drop the tank down, quite a trip. (though plug and play really) My knowledge comes more having a Renault 4, and on the forum it happens people want to convert a 6v car to 12v, but keep the original Fuel-tank and it sender. (or vice versa, put a newer fueltank in a 6v car.)

Does the signal from your sender go directly to the fuel gauge? If so, what type of gauge , analog current type?
Or, does the signal go to a "controller" that then drives the gauge?
Is the gauge in a vehicle? Which make and year model?

In a closed automotive fuel tank (excluding diesel) the vapor areas is 100% fuel vapor. Any water is either in solution or at the bottom of the tank (unlikely in today's fuel systems).

Gasoline is a quite nasty fluid. It can contain various solvents Including toluene, ethanol, maybe some methanol (but not much), butane etc. It can turn acidic when stored a long time.

The failure mechanism for a newer level sender construction is either mechanical smearing of the printed contacts, or small slivers of plating from one contact to the next.

Also the fuel passes right through the fuel pump, over the armature and around the brushes. Pump motors are slowly going to brushless but currently 99% of production are brush motors.

Toluene is not permitted anymore.

With all the ethanol in there these days i have to admit it will be in the solution.

Interesting, I wasn't aware of the change. Maybe happened after I left the industry. Still the list of fuel components that the fuel system could encounter was lengthy. Also we were testing for fuels that were available in other parts of the world. Brazil was the worst with 100% Ethanol. That is after they gave up on Methanol.

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