Reply to "Wiring the fuel guage!"

Well that was an interesting and very smelly day. Don't light a match around me tonight!!

First thing I did was drain the tank fully. I was suprised at the amount of crap that came out of it.

From an empty tank I filled 20 litres. In an 80 litre tank this should be 1/4 full. My current guage read just under half, and putting an 82ohm resister in series bought the guage back to just under 1/4.

Then another 20 litres went in and the standard setup read just under 3/4! 82ohm resistor again bought this to a little under 1/2 which was more accurate. All good I'm thinking.

Then.........

The third lot of fuel went in bringing total to 60 litres. Standard configuration went over full. 82ohm resistor did bugger all so i then tried 164 ohms in series and this bought the guage back to a perfect 3/4.

So that's just not working. There is no linear curve there.

So along the way I checked the voltage at the white/black wire that exits the sender.

0 Litres - 2.25v
20 Litres - 2.638v
40 Litres - 4.00v
60 Litres - 4.20v

So that sucks also. Again, no linear curve to base a fix on.

So those that are still keeping up, here was my next great plan.

Using the fuel pump this time, I drained the tank, 20 litres at a time.

I took out 53 litres before the fuel pump ran dry. So there is always 7 litres in the tank that the pump can't scavenge. That's poor design right there. That's like 40 kilometers on the road. Bloody long way to walk!

So tomorrow's job.

Should I base the fuel tank on the usable 73 litres? I need to continue down the resistor road until I find a suitable value to give me the closest accuracy at 1/4 tank and reasonable indication on 1/2 and 3/4.

To do this, do I go back to a 4 x 20 litre solution, or a 4 x 18.25 litre solution, knowing that the pump can't get the last 7 litres. Therefore is 1/4 tank really 20 litres, or 4/78 (18.25) litres.