Originally Posted by RichardV6
Peter see below for the complexity of fuel level system on a 3.7 Roadster.

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It's likely whilst different yours will have some commonality with above. Particularly note the two ground connections at the bottom serving the fuel level unit. They likely carry very small currents so would be susceptible to any connection resistance. They are not shared because the tiny current in one could affect the other. If you can find similar on yours re-make those connections or indeed any associated ground connections you find.

Break and re-make any connector you find in the area as well.

I just noticed this thread and I would like to second what Richard has said about earth connections.

When my car was new the fuel gauge was quite accurate. Over time it failed to register more than 3/4 full even when just topped up.
At a certain point I decided to change my dashboard and fit 3 separate instruments instead of the 3 in one original item. At that point I hoped that the new instrument would return to show full when the tank was full. After a lot of tribulation and discussions with Caerbont, the manufacturers of Smith's instruments, I was told that they had similar problems with London Taxis and the only solution that they had found was to run an earth wire from the sender on the tank direct to the battery.

I used an ohm meter to measure the resistance at the dash connection to the fuel gauge and filled the tank from empty (almost) 5 litres at a time whilst recording the resistance. In the end I discovered that there was no change for the last 15 litres added to the tank.

Fast forward to our last long tour away June. At a certain point, not long after filling the tank, I hit a large bump which shook the whole car. Much to my amazement I saw the fuel gauge started registering correctly and it has done so ever since.

I can only assume that the jolt of the bump moved some earth connection to the point at which the system was better earthed happy3 drive

Peter

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