Or this one for the fuel gauge -
http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=33920. You can sort the problem just by earthing the tank externally, on thee forward drivers side corner of the fuel tank is a hole alread on the welded seam/lip, you just need to connect an earthing lead from this to the chassis, ensuring its scraped back to a good metal to metal contact.
The charge & sediment could well be the alternator especially if it's related to the revs, worth checking all the connections are tight including the earth & field voltage, check the voltage output when it's running too.
Could be worth checking the sediment drain on the bottom of the fuel filter (the white plastic nut jobby, slacken it off carefully with a jar underneath & see if any water comes out or if it's just fuel).
You can't polish a turd - but you can roll it in glitter.