The gas gauge in my 1991 745t has always been slow. I figured it was designed that way to smooth out or average over the jiggles that occur in a moving vehicle. But last night I filled up the tank and came only a quarter of the way up and stayed there for 3 miles or so. After I made a right turn it came up to about 3/4 full and barely drifted noticeably higher for another 5 to 6 miles. Is something going wrong, and how do I fix it?
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Scott Cook - 1991 745T, 1985 RX-7 GSL-SE, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)

Mine did the same. I checked the resistence in the tank and the float seemed to be sticky. Going through a big bottle of Lucas Upper Cylinder Lubricant seemed to have lubed everything up so it moves OK.

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Paul NW Indiana '89 740 Turbo 120,000

I have a similar problem. My gauge has been slow to show a full tank for a while now. I have to drive about a mile to get it to read accurately.
It seemed to improve, but since I replaced the brushes on my alternator (voltage regulator), it's gotten bad again - or I just had stopped noticing it. I have a 90 740T, I don't have any idea why the gauge would go up so slowly.
I do know that when parked facing uphill, the gauge reads higher (or if driving uphill for several miles on a steady grade) and downhill it reads lower. I do have some fuel pump issues, I think my check valve might be bad, but maybe it's related to ITP. Pump is always on in KP2 unless the ITP is off -then it holds pressure after 3 seconds. Weird.

Anyway, if you learn anything about it, please PM me or post back or Email me at bigwilliex AT hotmail.com I have my filter set on exclusive, so put brickboard or volvo in the subject or it will probably be deleted.

Good Luck,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

I would think this is either some mechanical problem with excess gauge needle friction or the float is rubbing on something inside the tank. Since you've had it for a while and it seems to be getting worse I'd probably say it's the gauge.