Fuel Tank Issue
Operation of a typical in-tank fuel- level sending unit is based on variable resistance.
As the float moves up or down according to fuel level, the resistance in the sending
unit varies. Sulfur contaminants found in some of today’s gasolines can form
deposits on the sending unit, resulting in higher-than-intended resistance. The high
resistance could be misinterpreted as a high fuel level, when in fact the fuel level is
low. The driver may run out of fuel, even though the fuel gauge is not indicating low
or empty.
Contaminated and Clean Fuel Sending Unit
To help the protect fuel sending units from contamination. GMSPO offers GM Fuel
System Treatment PLUS P/N 88861011 and GM Upper Engine and Fuel Injector
Cleaner P/N 88861802.
To offset this effect, engineering has inverted the resistance values to the senders –
so now high resistance = low fuel levels and low resistance = high levels of fuel.
This was implemented on 2007 Corvettes and XLRs.
To offset this effect, engineering has inverted the resistance value on the fuel senders. This means that high resistance now indicates a low fuel level and low resistance indicates a
high fuel level.
So, if a deposit build-up adds to
sender resistance, the gauge will error in the
direction of indicating less fuel than is actually in the tank