gergstuff

I have been researching posts on fuel senders, in my case I have a '78 for which I recently cured a fuel leak, turned out to be a rotted vent hose.

Anyway, I get a needle that bounces around on the fuel gauge from time to time and after cleaning out the tank and reassembling after having given the sending unit a gentle cleaning my low fuel light is on even though the tank is completely full.

In studying the others posts I am trying to determine if the little arms on the float are supposed to be in constant contact with the very thin copper wires. Mine are not. So I wonder if that is causing the erratic gauge? Also, gauge only reads 3/4 full. I have seen several pictures but none that allow me to see if those little arms are up tight against those thin wires at all times.

Not sure on the low fuel light unless that could be something on the sender plug or some crud bridging the contacts at the bottom of the sender.

Comments?

Craig

Eplebnista

The fuel gauge needle moves as the resistance in the sender changes. The resistance changes as the float moves up or down along the two wires as the level of fuel in the tank changes. If the metal contacts on the float are not making contact with the two wires as the float moves up and down, your fuel needle will go wacky as the resistance goes to infinity when contact is lost.

On my 86 the warning light is supposed to be activated by the float contacting a switch at the bottom of the sender assembly and closing a switch.

Erratic fuel gauges are as common in 928s as fleas on a hound. The sending units have not distinguished themselves over time.

G.P.

The little arms on the float should be in constant contact with the very thin copper wires. From memory, the thin copper wire runs between the contacts on the float in such a way that the contacts on the float have spring pressure against the thin copper wire.
For the low fuel light, check all connections from the contacts at the bottom of the sender, all the way to the gauge.
When I got mine working I found about 80 ohms extra resistance in the wiring to the gauge. After fixing this the gauge works fine, all the way from full to empty.

gergstuff

Okay, my little arms were not in constant contact with the wires which certainly could explain the erratic gauge movement with the float bouncing around and only intermittent contact being realized. Will have to go through everything to get that pesky low fuel light extinguished.

Thanks for the input.