G 2500 3/4 Ton Van V8-6.5L DSL Turbo VIN F (1997)
Fuel Gauge: Initial Inspection and Diagnostic Overview
Circuit Operation - Analog Cluster
The pointer of the Fuel Gauge is moved by the magnetic fields of two coils, the E Coil and the F Coil. The two coils are oriented at right angles so that
the magnetic fields interfere with each other. Battery voltage is available from GAUGES Fuse 4 through the PNK (39) wire to the Instrument Cluster
when the Ignition Switch is in RUN or START. Current flows through the E Coil which places the pointer at E (empty) if there is little current through
the F Coil. If the current through the F Coil is high, then the pointer moves toward the F (full) indication.
The current that passes through the E Coil has two paths to ground. Some of the current can pass through the fixed resistance of the F Coil and to Ground
G101 through the BLK/WHT (451) wire. The rest of the current will go to ground through the variable resistance of the fuel sender element and the Fuel
Sender Buffer Module. The fuel sender element in the Fuel Pump and Fuel Sender (Gas) or in the Fuel Tank Level Sender (Diesel) produces a resistance
of approximately 4 ohms when the fuel tank is empty. With this low resistance, most current passes through the fuel sender and not the F Coil. If the tank
is full, then the fuel sender's resistance is approximately 90 ohms. With this high resistance, more current flows through the F Coil and the pointer moves
to K.
The Fuel Gauge's accuracy is adequate for normal operator usage in that it provides a reasonably accurate indication of level in the fuel tank. The Fuel
Sender Buffer Module is used for anti-sloshing to help increase fuel gauge performance. Gauge accuracy is not affected by changes in battery voltage.
However, the accuracy of the gauge can be influenced by non-linear construction in the fuel tank.
Troubleshooting Hints - Analog Cluster
1. Check condition of PARK LPS Fuse 9, TRANS Fuse 24, ILLUMINATION Fuse 14 and GAUGES Fuse 4. If any fuse is open, Locate and Repair
cause of overload and replace fuse.
2. Check that Grounds G101, G103, G109, and G201 are clean and tight.
3. Check that Instrument Cluster indicator and illumination lamp filaments are not open.
4. If the left turn indicator lamp, the right turn indicator lamp, the high beam indicator lamp, the fasten safety belts indicator lamp, and the
illumination lamps are not functional, then locate and repair the open in the BLK (150) wire between the Instrument Cluster and Ground G201.
5. If the CHECK GAUGES indicator lamp does not light under appropriate conditions, then Check the bulb filament for an open. If the bulb is not
open then replace the Instrument Cluster.
^
Check for a broken (or partially broken) wire inside the insulation which could cause system malfunction but prove GOOD in a Continuity/Voltage
check with a system disconnected. These Circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring
for a Voltage drop with the system operational (under load).
^
Check for proper installation of aftermarket electronic equipment which may affect the integrity of other system (Refer to "General
Troubleshooting Procedures,"). See: Diagrams/Diagnostic Aids
