Fuel Heater: Testing and Inspection

Fig 23 Fuel Heater Location:

NOTE: The fuel heater element, fuel heater relay and fuel heater temperature sensor are not controlled by the powertrain control module (PCM).

A malfunctioning fuel heater can cause a wax build-up in the fuel filter/water separator. Wax build-up in the filter/separator can cause engine starting problems and prevent the engine from revving up. It can also cause blue or white fog-like exhaust. If the heater is not operating in cold temperatures, the engine may not operate due to fuel waxing.

The fuel heater is located on the left side of the engine above the starter motor.

A minimum of 7 volts is required to operate the fuel heater. The resistance value of the heater element is less than 1 ohm (cold) and up to 1000 ohms warm.

Fig 24 Fuel Heater Assembly:

TESTING
1. Remove the electrical connector at the side of the fuel heater.
2. Using an ohmmeter check the resistance across the two terminals on the side of the heater.
- Resistance should be approximately 1 ohm (cold) to 1,000 ohms (warm).
3. With the electrical connector still unplugged from the fuel heater, check the electrical operation of the fuel temperature sensor.
- Proceed to next step:
4. Using an ohmmeter, check the resistance across the two terminals in the pigtail wire harness coming from the fuel temperature sensor.
- The sensor circuit should be open if the fuel temperature is above 80 degrees.
- The sensor circuit should be closed if the fuel temperature is below 40 degrees.
5. Check for 12 volts at the disconnected temperature sensor connector with the ignition key ON.
- Refer to Diagrams for electrical schematics.
6. With ignition ON, check for 12 volts at the fuel heater relay connector.

Fig 25 Fuel Heater Relay Location:

7. Check operation of the fuel heater relay.