Fuel Guage goes beserk!

I have a 99 Redeo, 50K miles, no problems til now. The fuel gauge has gone beserk, the guage indicates a full tank for about 20 or 30 miles after completely filling the tank Suddendly the guage goes to zero and the
flashing fuel pump light flashes on and off, this scares the heck out of you the first time you see this problem. I had it into the Isuzu dealer and he says there is a module that is bad, passes the indication from the sensor module in the opposite direction. The dealer doesn't have the module and says it is a 3 hour job to remove the fuel tank and replace the module, the dealer is to call when the part comes. I would surely appreciate any information from anyone with experience with this or a similiar problem. I am not looking forward to a 3 hour job of removing and replacing the fuel tank for the purpose of replacing the faulty indication if that is the problem. Labor is 80 bucks per hour. I suspect there is a bad electrical connection, or a bad float, other wise why would there be a normal indication of fuel level although it lasts for only minutes, seems to me that bad is bad now and for always. Seems we have an intermitten condition, Normal condition and then abnormal. Your thoughts and information would be appreciated. maybe the dealer is correct, They have only been servicing Isuzu's for two weeks having bought out the former Isuzu dealership Fred
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Sounds like the sender in the tank I had the same in an 89 Bighorn except that I got 150km before the gauge punged to the bottom.I dont know about the Rodeo but the bighorn sender is on the front of the tank and only 5 min to remove or refit.
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I have a 88' pickup that works similar, but no flashing lights. The fuel gauge works when I fill the truck up, but at about 40 miles it slowly works it way down to indicate empty. I use the odometer to let me know when to get gas. The empty light comes on at about 290 miles. Steve
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It's the sending unit. It has gotten fuel-logged and must be replaced. Good luck!

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wrote:

I had this problem on a different make/model (93 Taurus), my "Southern Engineering" solution was to drain the tank by removing the plug at the bottom of the tank, draining and leaving it open to air for a few days to let everything completely dry out, replacing the plug and refilling the tank with all new gas.
And no.. I didnt figure this out on my own.. a mechanic friend pointed out the problem, and suggested that I have him replace it, but the unit was more than my budget allowed at the time, and since I had another vehicle to drive in it's place (my Rodeo :) ) I just drained the tank and .. Lots of "gunk"And you would'nt BELIEVE the difference it's made. Runs smooth as silk too now, as well as the guage functions properly
(I also poured two bottles of gas treatment and one bottle of water remover AFTER I had drained the tank, and jumped up and down on the back of the vehicle to slosh it around.. lots of "gunk" came out....)
Chuck Burns
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