Crazy Fuel Gauge

[kyle6086]

its a fuel sending unit...it did the same thing on mine and my sister truck had to replace it then worked perfectly fine...btw i think i paid around 380 for mine

[kst3v3n]

Do the "wiggle" test on the tank harness, while watching for a change.
Check the wire connectors, remove the retainig device, release the pins from the plug, and check for corrossion. I have been finding al sorts of OEM plug connectors that are corroded and really screwing up my ride.
The sending unit could be bad, worn down, most likely dirty of fuel varnish on the fingers, TRY "Seafoam" I would bet on wireing, only cuz i had one and in my hand all day. And them damn connectors have been giving me fits.

More details if you want:

I have a swaped 04 5.3/4l60e into a 88 k5 with a 04 cluster, Well aftera few years I just got around to finishing the sending unit today, I didnt take any pics though, sorry. I was chaseing a fulke huch about my fuel pump any way.
The actuall sending unit and float part is held onto the fixture that goes into the tank by a couple clips, You could change just that part of it from a bone yard unit. Some body makes that part brand new every day for DELPHI but i dont know who. There are two real delicate metal fingers that ride up and down on a serarted contact strip. The fingers are attached to the tank float. The strip has a wire that goes to ground and the fingers have a wire that gets 5 volts from the pcm. The resistance changes as the float goes up and down, the fingers are in differnt spots as the level changes.

The pcm is detecting change in resistance, at the tank unit, thru the connections, thru any corrosion, accross bad wires could be any where the pcm dont know and dont care, just the change. The guage is reflecting the change the pcm is seeing, also could be The dash, fuel indicator is class 2 serial data, some thing is getting lost between the pcm and the fuel needle.

Them Delphi/packard connectors are nice for a while, they are all sealed and any moisture that does happen to get in cant get out. They have alot of "tsb"s that have to do with these connectors, all over the truck/car. The plating used, the crimping methods used, the size of the seal used vs the insulation thickness of the wire.