Odd Fuel Gauge Behavior

Joined
26 February 2006
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5,533
Location
California Republic
This afternoon I gas up full tank (Woohoo! <$2.50/gal!) and went on a long drive, more like a commute on the highway. Anyhow everything was working fine and on my return trip @ mile 86 on the odometer, I look at the gas gauge and see that's sitting very slightly above half tank. Odd. Why is it eatting gas at that rate when I saw it at 2 clicks under full just 30-40 or so miles ago? I run some numbers in my head and talk myself into believing that maybe I didn't gas up all the way or the last half will go down ALOT slower. I change into the left lane, pass a slower car on the smooth highway. Look at my gauge and it was at 2-3 clicks below full..... where it's SUPPOSED to be. How odd. No hard jarring, bumps, change in elevation, or anything major, just smooth cruising on the freeway. From the time I noticed it, to the time it corrected it self was MAYBE 2 minutes. Just odd. The rest of the trip home it worked perfect though........ Still does........
 
I noticed that my '96 takes many minutes (WAG - 2 to 5) to indicate more than 1/2 tank of gas after I fill it up. Eventually it reads the correct value. So, there is a very large damping factor (delay) in the gas gage system so it is not affected by sharp corners, hills, etc.

But I take it in your case you were driving for many minutes when you noticed the unusually low level indication? If it was only a few minutes, were you parked on a hill before you started driving?

I'd simply keep track of this and see if it occurs again.

Anyone else have a more dire experience with this?

Frank
'96 NSX-T, red/tan
 
Well the car had been running for atleast 10-15 miles when I noticed it. But it never happened before.

Here's another addition , it happened again last night on the same stretch of highway on just about the exact same location. How odd. It didn't happen any other time, just at this same location. Simple flat straight stretch of highway, No hills or mountains for a LONG way. Almost like a Bermuda Triangle. How strange.

I wasn't running the same fuel load either. This time I was running about..... 3-5 gallons less.
 
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Now you are getting into more serious troubleshooting. If all other gages (voltmeter, oil pressure, coolant temp) are working OK, its not the 12V or ground to the gauge assembly. Items that could be the problem:
1. Fuel gauge sending unit - sticking or "flat spots"
2. Loose ground to the sending unit
3. Loose connection somewhere between the sending unit and the fuel gauge.

Per the manual, C486 is accessible at the rear bulkhead, with the panel removed (Photo 86 in the '95 electrical troubleshooting manual). And, the 3-P connector on the sender can be reached by removing the fuel tank access panel (3 screws). You can measure the resistance vs tank level at that connector. You can also remove the sending unit and measure per PP 23-134, 135 of the '95 shop manual.

I'm an electrical engineer, and as such am crazy enough to dig into this type of trouble shooting. :rolleyes: If electric circuits are not your thing, then its time to find a good auto electrics person. Or, simply drop by my house the next time you are driving your car through NJ. :biggrin:

Frank
'96 NSX-T, red/tan
 
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