Circuit/System Testing

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

1. Disconnect the fuel heater harness connector from the top of the fuel filter/heater element housing.
2. Turn ON the ignition with the engine OFF.
3. Probe the fuel heater ignition 1 voltage circuit with a test lamp connected to a good ground.
   • If the test lamp did not illuminate repair the short to ground or open in the ignition 1 voltage circuit.
4. Probe the fuel heater ground circuit at the fuel filter/heater element housing with a test lamp connected to battery voltage.
   • If the test lamp did not illuminate repair the open in the ground circuit between the fuel filter/heater element housing and the engine ground.
5. Remove the fuel filter from the fuel filter/heater element housing. Test the ignition 1 voltage circuit and the ground circuit for an open in the fuel filter/heater element housing.
   • If either circuit tested open replace the fuel filter/heater element housing.
6. If all circuits test normal, test the fuel heater thermostatic switch for proper operation. Refer to Component Testing .