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Fuel gauge adjustment

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RDKeysor

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The fuel gauge in my BN7 reads empty when there are about five gallons remaining in the tank. This was discovered, of course, by refilling the tank when it registers empty. I've read the previous threads, which by and large discuss dealing with the dash instrument. That discussion of the instrument's fragility doesn't encourage me to try that approach. I know my car has a new tank, and my inclination is to remove the tank float and readjust the float arm. I did this successfully with a JC Whitney-sourced fuel sender in a Volvo years ago, and I recall that I was able to get it to read reasonably accurately. Opinions!
 
Adjusting the gauge coils isn't that difficult or risky. Take out the drivers seat and have something comfy to lie on helps. And a light. The gauge ground path is through its hold-down bracket on the back and this can get in the way a little but you need to be sure it is grounded while adjusting it or the reading will be wrong. It is also relatively easy to short the live feed terminal onto the bracket while moving it out of the way.

Suggestions: Draw around the present location of the two little nuts before loosening them. Use a 1/4 drive socket with a screwdriver-handle attachment to loosen them one at a time but only just a little until they can slide, maybe 1/4 to 1/2 a turn and no more. Empty the tank and know that the float is dropping down into the lower/forward recess fully and that the sender is grounded properly to the chassis. The original fuel pump is the ground path via the fuel line and if you have a replacement pump fitted with flexible hoses then the gauge won't ground properly.

It is worthwhile removing the sender first off and grounding it with a wire, then running it slowly through the full travel. If there are any glitches in the gauge movement then you can rub the sides of the coil under the sender top cover with rolled up 1500 grit sandpaper to remove dirt. If you haven't let the tank run right down to empty for a long time then it is likely that the wipers haven't rubbed on the coil there for a while and there may be a dirt buildup which will stop the gauge receiving the right signal.

If you haven't had the fuel sender out for a long time then the hold-down screws may be frozen in. They snap off real easy and then the job turns ugly. Perhaps heating them up with a big soldering iron might be enough to free them up if a regular screwdriver won't move them.

Andy.
 
57_BN4 said:
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It is worthwhile removing the sender first off and grounding it with a wire, then running it slowly through the full travel. If there are any glitches in the gauge movement then you can rub the sides of the coil under the sender top cover with rolled up 1500 grit sandpaper to remove dirt. If you haven't let the tank run right down to empty for a long time then it is likely that the wipers haven't rubbed on the coil there for a while and there may be a dirt buildup which will stop the gauge receiving the right signal.

Andy.
Click to expand...

Adding to the above excellent advice - you might want to run a ground wire from one of the sender top screws to the chassis.
 
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