Inaccurate fuel gauge/low fuel light

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My fuel low level light was coming on too early for the fuel meter level reading

Thought some may be interested in the rig I set up for getting a real time look at what the fuel gauge was doing out of the vehicle.

I first checked the parameters as per the the manual [see chart attached] and that appeared to be fairly close to spec, a little short on ohms at both ends but near enough. I still wanted to see what was happening though so I decided to set up a test rig and observe first hand what was going on.

The first thing to do was replicate a fuel tank and it occurred to me that the simplest way of doing so was a length of 50mm PVC pipe cut to a slightly longer length than that of the sender and fit an end cap to it. Voila. A petrol tank. I then tapped in a barb at the bottom and fitted a length of fuel line so I could control the amount of fuel in the chamber and watch, when wired up, how the gauge responded to flow. It would also show when the low fuel light would activate and at what level on the meter.

Turned out to be a worthwhile exercise as it did demonstrate that the components are working correctly. If it still reads wrong in the vehicle I can only assume that there is something else going on. It did conclusively prove to me that the light is the main thing that is to be believed as it cannot be wrong. Having pulled the sender apart and checked out the way it activates it can never be wrong.

I realize that some might figure this may be a bit anal but those sort problems are always in front of you when you drive the car and to me at least, are a constant source of annoyance. Can never rest until I get get to bottom of the problem. It may never marry up properly whilst in position but doesn't really matter the main thing is that I now fully understand how it works and what is going on with it.

Dave