S15 Fuel gauge erratic

[mr402]

I'm looking for some diagnosis help. The fuel gauge in my 2000 Jimmy reads accurate only when full. When in Park or Neutral the gauge will bounce around. When in gear it stops bouncing but won't read accurately. I'm certain its' input related as the trip computer is also inaccurate and changes with the gauge. I plan to pull the tank this weekend and do some voltage measurements and a few tests at the wiring.

Am I looking at a sending unit or do these have a separate voltage regulator for the fuel gauge. All other gauges are working fine and I only have 53k miles on it. If this were only my 71 it would be a piece of cake.

[70ChevyChris]

mr402, what did you find out with your fuel gauge? About a month ago the temperature dropped down to 0 for about 4 days and ever since, my fuel gauge hasn't worked right. Not sure if the cold weather is related but it just so happened that it was the coldest its been for the 3 years I've owned the truck when it happened.

Shows full all of the time unless I'm sitting at a stoplight, then it drops to empty and the low fuel dummy light comes on.

If anyone knows what the problem is, your advise will be appreciated.

btw, it is a 99 GMC Sonoma

[Purduegmc]

I have been having problems with my fuel gauge in my 2000 GMC 1500 also. Mine acts slightly different, At times in randomly drops and says that it has low fuel. It happens mostly after filling up, but it has happend at other times.

[stan79chevy]

Its a pretty common thing. My 00 zr2 has been doing it for a while. The problem is the moduel on the pump. You do not have to replace the whole fuel pump. You can get just the replacement moduel for around 60 bucks. Taking the bed off is definately the easiest way (atleast for an s10 yours may be different) I went all through mine with my meter looking for a loose wire or something because it was so erratic and didnt have a consistent pattern. Turned out to be the moduel.

stan