It is the fuel sender - most likely, there is a patch on the fuel sender contact strip that has gunk on it (fungus) which makes for a bad connection. The sending unit is serviceable, there is a DIY or two on removing the sending unit. You might want to try running some soltron or biobor through the tank first to see if that solves the issue...did for me.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth