C 2500 Suburban 2WD V8-6.5L DSL Turbo VIN F (1995)
Water In Fuel Circuit Check
CIRCUIT DESCRIPTION
The fuel manager/filter assembly consists of the fuel heater, the water in fuel sensor, and a filter. The filter contains the "coalescer" (the device that
combines small droplets of water into larger ones) and the filter/separator.
A fuel lift pump delivers diesel fuel from the tank to the fuel filter. As fuel enters the filter, it passes first through the fuel heater. The heater
contains a thermostatic switch. The switch opens or closes to turn the heater "OFF" or "ON," depending on the temperature of the fuel.
The fuel then passes through the filter. Next the fuel flows through the water coalescer. Here the droplets of water in the fuel are combined into
larger drops, the drops fall to the water reservoir in the filter. When fuel flows from the fuel manager/filter assembly to the injection pump, it is
clean and free of water.
The solid-state water in fuel sensor supplies voltage to a probe. When the probe touches water, the module closes a switch. This completes a
circuit to ground to light the "Water in Fuel" lamp.
A time delay circuit in the water in fuel module grounds the lamp briefly to test the bulb each time the system is turned "ON." The fuel heater is
operated by a built-in thermostatic switch. When the switch is closed, battery voltage is supplied to the heater.
CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test will determine if CKT 39 is open.
2. This step will determine if the ground CKT 150 is OK.
3. This step will determine if fuse, bulb, and wiring are OK.
