my fuel guage does not work porperly, it reads full till its copmpletely empty, what could be causing this? 92 b2200

 

Usually the sending unit is bad, very common on these as they age. Get out your multimeter (if you don't have one, RUN to Sears this morning and buy a digital one on sale half-price for $10, worth its weight in gold, I have three at various places). Set up in the resistance or ohms scale, touch the leads together, and record any ohms resistance (subtract this amount from subsequent measurements). Sending unit out of truck; hook up the multimeter leads and physically move the float up and down, measuring the ohms resistance at various positions. Here's the factory ohms resistance at those positions:
Empty: 103-117 ohms
Middle: 28.5-36.5 ohms
Full: 1-5 ohms

Apparently there are different sending units for the standard, long bed, and cab plus versions as the manual lists different distances for the arm to be in for those three positions for exact measurements. There should not be areas of zero resistance in between either, should be relatively linear with regards to float position on a good unit. To fully check out the gauge, one must apply 7 ohms for full, 32,5 ohms for mid-way, and 95 ohms for empty, but that requires a different, more expensive tool.

 

i figured it was but i was hoping there was a cheaper quick fix solution to this problem. maybe somehting funny with mazdas or somehting.