The fuel filter/heater element housing consists of a water separator, a hand prime pump, fuel heater element and a filter element . Fuel passes through the fuel heater, which is operated by a built-in thermostatic switch. The thermostatic switch opens or closes to turn the heater ON or OFF, depending on temperature. Fuel then passes through the filter and the water coalescer, where the droplets of water in the fuel combine into larger drops that fall into the water reservoir in the filter. When fuel flows to the fuel injection pump, the fuel is clean and free of water.

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

Check the Water in Fuel lamp for proper operation. Refer to Water-in-Fuel Lamp Always On .

1. Turn ON the ignition , with the engine OFF.
2. Disconnect the fuel heater connector.
3. With the fuel temperature above 21°C (70°F), test for continuity between the ignition 1 voltage terminal and the fuel filter/heater element housing.

⇒	If continuity was present, the thermostatic switch is stuck ON. Replace the fuel heater element.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Heater Replacement