QuestionI have a 2001 Chevy 1500 Truck, 350(ish) v8 engine. The gas gage has started to jump back and forth. Does not matter if full or empty. It is intermittent, but does it often. Local guy said fuel pump, but I would think it would be a ball or something near the tank? (But I dont know), any ideas? Thanks by the way.
AnswerHi
here is a GM bulletin on a similar issue.
Fuel gauge may be inaccurate or drops to empty (E) and the low fuel light comes on. Further analysis may reveal that this condition is most apparent when the gauge is at or below the quarter (1/4) tank mark.
Recommendation/Instructions:
Try to duplicate the concern by driving the vehicle a short distance in reverse and then stopping (to make fuel slosh), shifting transmission to park or neutral and then shifting to drive. The fuel gauge will have a tendency to read lower than actual. The gauge will take a few minutes to show the actual fuel level. The VCM/PCM is the buffer for the fuel gauge.
On a Automatic Transmission no buffering takes place when the transmission is in park or neutral. This is a NORMAL characteristic & NO repairs are necessary.
On a Manual Transmissions, the fuel gauge is buffered in all gears and neutral. Since the VCM/PCM has no way to know what gear it is in, there is a timer which starts to count up when the clutch is depressed. When this timer reaches its calibrated value (this value will vary), the filtering switches to the "fast" filter (no buffering). When the clutch is releases the filter then switches to the slow filter (system is Buffered). This is a NORMAL characteristic & NO repairs are necessary.
If this does not explain your condition, the local mechanic was partially correct.
It will need the Fuel level sender unit replaced.It is located on the pump module.
I hope this helps.
Good Luck
Pawl
