Thursday, August 26, 2021

Fuel Level Wonkiness

I've been working to get the fuel level sender in my car calibrated correctly.  That's not gone quite so well.  The idea is to have it feed into the AIM dash.  As mentioned before, that's a little more involved than simply plugging it in and going.  The sender seems a bit wonky if I'm honest so it was hard to get reasonable, consistent voltages for all of the different fuel levels.

My process also kind of sucked ass and I can do much better.  I started with the tank empty, then filled it gallon-by-gallon and read off values.  I spilled fuel, it wasn't a clean way to do thing.  Next go I'm going to fill the tank (~8 gallons), jack the car up onto stands front and rear, then drain the tank gallon-by-gallon.  That should be a lot less messy and should cause a lot less sloshing in the tank which I think was causing some reading issue with the fuel level sender.

This is all a project for FutureMe, however.

I've ordered a new fuel level sender and gauge from ETB Instruments in the UK, fairly inexpensive thing to do. At the very least it will get me a known good gauge and sender combination regardless of anything else.

The new sensor should read:

  • 260 ohms, empty ( 0.631v w/ 1.8K ohm pull-up )
  • 20 ohms, full ( 0.055v w/ 1.8K ohm pull-up )

Process:

  1. Install the new sensor.
  2. Fill the tank with 30L of petrol. (~8 Gal US)
  3. Record ohms on the sensor, drain one gallon
    1. Repeat until empty.
  4. Calculate the calibration table from the recorded ohm.
This process should give a good enough calibration for the AIM dash.

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