Pos. | spare part no | Name |
1 | - | Fuel temperature sensor |
2 | - | Fuel supply to the high pressure pump |
3 | - | Condensate drain screw |
4 | - | Fuel filter |
5 | - | Fuel filter shield |
6 | - | Condensate drain port |
7 | - | Fuel supply from the tank |
8 | - | Fuel return to tank |
9 | - | Fuel return from the high pressure fuel system |
The fuel filter is located forward on the right side of the engine compartment and is mounted on the engine support bracket. A protective shield is installed to protect the filter in the event of a frontal collision. The filter is made of heat-resistant and fire-resistant durable plastic. It contains a paper filter element.
The fuel temperature sensor is built into the fuel supply port on the fuel filter. The sensor provides the ECM with a signal whose voltage is proportional to the actual fuel temperature. The signal is used by the ECM, along with signals from other vehicle sensors, to calculate the actual fuel pressure required in the high pressure fuel rail. For more information see the chapter: Electronic Engine Controls - 2.2L Diesel (303-14 Electronic Engine Controls - 2.2L Diesel, Description and function).
The fuel filter has a drain screw and a drain port. The drain screw allows the condensate present in the fuel to be drained off at prescribed service intervals.
Fuel filter preheat function
The fuel filter features a pre-heating function that operates when the return fuel temperature is below 10°C. The preheat function recirculates some of the return fuel from the high pressure fuel system through the filter to prevent fuel waxing and improve engine performance in cold running.
Pos. | spare part no | Name |
A | - | Fuel return temperature below 10°C |
B | - | Fuel return temperature above 20°C |
1 | - | Fuel return to tank |
2 | - | Fuel return port outlet |
3 | - | Fuel return port bypass |
4 | - | fuel filter head |
5 | - | Fuel return from the high pressure fuel system |
6 | - | Thermostatic valve with paraffin filling (bypass open) |
7 | - | Thermostatic valve with paraffin filling (bypass closed) |
The fuel filter head contains a paraffin-filled, spring-loaded thermostatic valve located in the fuel return passage between the high pressure fuel system and the fuel tank return ports. The thermostatic valve is located in the bypass port that connects the fuel return port to the fuel filter chamber.
The thermostatic valve is actuated depending on the temperature of the fuel in the fuel return passage, sensed on the upper side of the thermostatic valve, and the fuel supply temperature in the filter chamber, sensed on the lower side of the thermostatic valve.
The amount of return fuel recirculated through the filter chamber is proportional to the temperature of the return fuel and the position of the thermostatic valve.
Fuel return temperature | Percentage of fuel return to the tank | Percentage of recycled fuel |
Less than 10°C | 5 - 10% | 90 - 95% |
More than 20°C | 95 - 100% | 0 - 5% |
Fuel temperature is less than 10°C
The thermostat is in the compressed position and held in the bypass port seat. The top side of the thermostatic valve nearly closes the fuel return port outlet due to the position of the thermostatic valve and the light force applied by the spring.
A large proportion of the fuel returned to the filter passes through the open bypass port and is recirculated in the fuel filter chamber. A small portion of the return fuel is allowed to pass through the thermostatic valve and is directed through the fuel return port outlet to the fuel tank.
Fuel passing through the fuel return port outlet also provides lubrication to the thermostatic valve stem.
Fuel temperature over 20°C
The thermostatic valve expands against spring force to nearly plug the fuel return port bypass and opens the fuel return port outlet.
A small proportion of the fuel returned to the filter passes through the partially open bypass port and is recirculated in the fuel filter chamber. A large proportion of the returned fuel passes through the thermostatic valve and is directed through the outlet of the fuel return port to the fuel tank.
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