DD15 Engine

Section 3.2 Fuel Filter Module

Section 3.2
Fuel Filter Module

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 1. Water-in-Fuel Sensor‪

11. Return Connection from HP Pump‪

 2. Fuel Priming Valve‪

12. Fuel Connection to LP Pump‪

 3. Assembly Valves‪

13. Fuel Connection from LP Pump‪

 4. Hand Primer Pump‪

14. Amplifier Bracket‪

 5. Water Separator‪

15. Supply Fuel Temperature Sensor‪

 6. Final Filter‪

16. Fuel Prefilter‪

 7. Return from PLV, Injector Needle and Amplifier‪

17. Mechanical Drain Valve‪

 8. Emergency Lubrication Connection for HP Pump‪

A. Fuel Feed Suction Side‪

 9. Fuel Connection to HP Pump‪

B. Fuel Feed Pressure Side‪

10. Fuel Accumulator‪

C. Fuel Return Flow‪

The fuel filter module is located on the left side of the crankcase. The fuel filter module (1) separates out water in the fuel and filters out dirt particles in two stages. The fuel filter module (1) consists of the following components: ‪

  • Fuel prefilter (16) where large dirt particles are removed from the fuel.
  • Water separator (5) with water collector through where water in the fuel is separated.
  • Final filter (6) where small dirt particles are removed from the fuel.
  • The fuel accumulator (10) gathers fuel from all return lines and passes it through a bypass valve to either the fuel prefilter (16) or to the fuel tank.
  • The hand-operated primer pump (4) allows for priming the system when a filter is changed or when the fuel system is run dry.
  • The fuel priming valve (2) can also be used after replacing a fuel filter or when the fuel system is run dry.
  • Assembly valves (3) which prevents fuel from escaping when disassembling the fuel lines between the fuel tank and the fuel filter module (1).

Section 3.2.1
Fuel Prefilter

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 1. Filter Element‪

 5. Fuel Inlet‪

 2. Check Ball‪

 D. Unfiltered Fuel‪

 3. Bypass Valve‪

 E. Prefiltered Fuel.‪

 4. Fuel Outlet‪

Unfiltered fuel (D) passes through the fuel inlet (5) into the fuel prefilter. Fuel entering the prefilter pushes the check ball (2) off its seat allowing flow through the filter element (1) from inside to outside.‪

The larger dirt particles remain in the filter element (1) and the precleaned fuel (E) flows through the fuel outlet (4) to the low pressure pump. The check ball (2) has the task of preventing fuel from draining out of the fuel inlet circuit when the engine is stopped. If the fuel flow is blocked, the prefilter can be bypassed via the opened bypass valve (3) located at the top of the filter. When removing the filter element (1) a drain to the fuel accumulator is opened so the fuel can flow out of the fuel prefilter housing.‪

Section 3.2.2
Water Separator/Coalescer

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 1. Water Bowl‪

 6. Final Filter‪

 2. Fuel In (from feed pump)‪

 7. Coolant Connection‪

 3. Water Separator (Coalescer)‪

 7. Supply Fuel Temperature Sensor‪

 4. Air Purge (bore dia 0.4 mm)‪

 9. Mechanical Drain Valve‪

 5. Fuel Transfer Bore‪

The water separator element (3) consists of many layers and has the task of separating out the water contained in the fuel. The water separator element (3) has fuel flowing from inside to the outside. The special construction ensures that small water droplets either remain in the water separator element (3) or bind themselves to already retained water droplets. Small dirt particles are also filtered out due to the construction.‪

In order to ensure that the water droplets can sink downwards into the water collector (1), it is essential that the flow rate of the fuel is reduced. This is achieved purely by the design of the housing. The flow rate of the fuel is increased again due to the shape of the housing as it flows to the final filter element (6). Water level in the water collector (1) is detected by using a Water-in-Fuel Sensor. If the Motor Control Module (MCM) detects excessive water in the water collector (1) it will transmit an appropriate message to illuminate an indicator lamp.‪

The driver will need to drain the water using the mechanical drain valve (9). A ventilation bore (4) located above the water separator element (3) serves to divert the trapped air in the water separator (3) and routes it to fuel collector (5) where it can be returned via the fuel return line to the fuel tank. The ventilation bore (4) also guarantees full use of the water separator element (3). When removing the water separator element (3) a drain (9) to the fuel accumulator (5) is opened so that fuel can flow out of the water separator housing.‪

Section 3.2.3
Water-in-Fuel Sensor

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 1. Water-in-Fuel Sensor‪

 2. Sensor Electrode‪

The Water-in-Fuel Sensor (1) determines the electrical resistance between the two sensor electrodes (2). If the water level increases in the water separator up to the sensor electrodes (2) the electrical resistance drops. This change of resistance is detected by the MCM. If the critical water level is reached, an indicator light on the sensor will illuminate. In order to avoid electrolysis (corrosion of the electrodes), AC voltage is used.‪

Section 3.2.4
Final Filter

The final filter element consists of many layers. Fuel flow through the filter element is from the outside to inside. The smallest dirt particles are filtered out at a very high separation rate by the final filter element. Just like the prefilter and water separator, the final filter housing has a ventilation bore. This ventilation bore allows full use of the filter media. When removing the final filter element a drain bore to the fuel accumulator is opened so the fuel can flow out of the fuel filter housing. The cleaned fuel is supplied to the fuel high pressure pump through an overflow bore in the inner dome. The high position of the overflow bore in the inner dome ensures that the no unclean fuel can reach the fuel high pressure pump.‪

Section 3.2.5
Fuel Hand Primer

A fuel hand primer is incorporated into the center section of the fuel filter module. The hand primer can be used anytime the system is run out of fuel or after a fuel filter change. Average time to fill the module after a filter change is approximately 3 minutes or 200 to 300 pumps. Fuel for the priming circuit is taken after the prefilter and is deposited between the water separator and final filter.‪

Section 3.2.6
Fuel Priming Valve

A fuel priming valve is also incorporated into the fuel filter module. This port can be used to prime the fuel system in the event of an engine running out of fuel or after a fuel filter change. The fuel priming valve feeds fuel into the fuel filter module after the water separator, but before the final filter. The design of the fuel priming valve is the same as current production.‪

Section 3.2.7
Supply Fuel Temperature Sensor

The Supply Fuel Temperature Sensor is located on the left side of the crankcase on the fuel filter module. The MCM detects the current temperature of the fuel via the fuel temperature sensor. There is an NTC resistor inside the Supply Fuel Temperature Sensor. NTC stands for "Negative Temperature Coefficient" and means that the electrical resistance falls as the temperature increases.‪


DD15 Fuel System Technician's Guide - DDC-SVC-MAN-0037
Generated on 10-13-2008

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