Just replaced my fuel gauge sending unit and thought my fuel gauge problems were over, but not so. Now my gauge reads Full all the time. My shop manual says the problem is my instrument cluster isn't grounded, but it is. All other gauges and lighting works fine. Anyone else ever seen this problem? TIA
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Re: Fuel Gauge Always Reads Full
Yes, had the same problem with an 82 collector car. It was the fuel tank rubber liner floating loose and holding up the gauge. Showed full all the time. I had to put a stick in the tank to see how much gas I had. Is yours a 78-82 with the liner in the tank? -
Re: Fuel Gauge Always Reads Full
Take the wire from the sending unit loose at the gauge. With the ignition on, connect and disconnect a test lead from the sender terminal on the gauge to a known good ground. If the gauge works properly, the gauge should read empty with the lead disconnected, and full with it connected. If the gauge is good, your wire from the sender could be grounded somewhere.Comment
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Re: Fuel Gauge Always Reads Full
Fred,
I know there's some stuff in the Archives about this, but not exactly sure what it would be under. I had a similar problem with my 68 fuel gauge. The wafer thin thermostatic coil, about 1" long, on the back of the gauge had aged, flaked, and was falling apart. The hair-thin coiled wire was touching itself (can I say that?) and giving me a more-than-full reading at all times.
If you find this to be your problem, don't bother calling all the large part suppliers for an insulting Tech conversation or a $50 offer to rebuild your gauge. I found a supplier that will sell you just the $10 thermo-coil that you need. It is Red Line Gauge and Clock Repair at Humbolt, Tennessee, 800-375-2310. TBarr #24014Comment
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Re: Add on
As you can tell, by no stretch of the imagination am I anywhere qualified to have an intellegent conversation about electronics, but the "thermostatic coil" I referred to, if I remember correctly, was sent to me as a "resistor". TBarr #24014Comment
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Re: Fuel Gauge Always Reads Full
Before we go to too much detail on how to troubleshoot your situation, it'd be nice to know WHAT THE HECK WE'RE working on. Straight axle and shark cars use one form of fuel gauge circuitry and mid-year cars another. Difference is early/late cars have gauge that's simple ammeter mounted in series to variable resistor in the tank. Mid-year cars use unique Whetstone bridge circuit topology (gauge responds to the degree of imbalance in the bridge impedance legs).
If you have a mid year (can tell because the tank gauge has more than one electrical contact lugs) then it IS possible for gauge to read full all the time due to faulty dash ground and the 'acid test' of 'my other dash insturments are working' doesn't get it....
Ground from fuel gauge to dash has to be correct and low resistance AND master ground from dash instrument cluster to electrical (chassis ground) also has to be proper. If any of these conditions exist, ground on fuel gauge to dash cluster is faulty (one of two mounting screws is ground, the other is dummy for mechanical rigidity), higher than 'normal' instrument cluster impedance continuity to electrical ground, or intermittent continuity from dash gauge to tank sender can generate symptoms you see on mid-year setup unlike straight axle or shark.....Comment
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Re: Fuel Gauge Always Reads Full
I have had this problem on my 63 and 81 both are dramatically different when it comes to the repair. Check out this web address for some 81 tips http://l81registry.com/gasgauge.htm The fix for the 63 was to replace the gauge. Eric #3,182
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