MBE 4000 DDEC VI Troubleshooting – Section 3.4 Test #2 Fuel Pressure Test At the Fuel Filter

Section 3.4
Test #2 Fuel Pressure Test At the Fuel Filter

The following test set-up and test will determine the fuel pressure at the fuel filter.‪

Section 3.4.1
Test #2 Set-up

The following test set-up to determine the fuel pressure at the fuel filter.‪

1. Adaptor Fitting (915039012205)‪	4. Fuel Line — Filter to Main Gallery‪
2. Fuel Filter‪	5. Electronic Unit Pump‪
3. Gage and Line (J-46372 and J-46378)‪

Figure 1. Fuel Filter Pressure Inlet Measurement Set-up

1. Fuel filter inlet pressure reading set-up before the filter.
   1. Remove the banjo bolt and washers at the fuel filter inlet line. See Figure "Fuel Filter Pressure Inlet Measurement Set-up" .
   2. Install the adaptor fitting from kit (J-46377) and washers in the fuel filter inlet line. Tighten fitting securely. See Figure "Fuel Filter Pressure Inlet Measurement Set-up" .

      Note: The adaptor fitting used is not a special tool and is not included in the Fuel Adaptor Parts Kit (J-46377) . The fitting can be ordered from Canton PDC under part number 915039012205.

   3. Connect the high-pressure fuel line (J-46372) and gauge (J-46378) to the adaptor.
   4. Perform the fuel pressure test at the fuel filter. Refer to "3.4.2 Performing Test #2 Fuel Pressure Test at the Fuel Filter" .
2. Fuel filter outlet pressure reading set-up.
   

   1. Adaptor Fitting (915039012205)‪	4. Fuel Line — Filter to Main Gallery‪
   2. Fuel Filter‪	5. Electronic Unit Pump‪
   3. Gage and Line (J-46372 and J-46378)‪

   Figure 2. Fuel Filter Pressure Outlet Measurement Set-up

   1. Remove the banjo bolt and washers at the fuel filter outlet line. See Figure "Fuel Filter Pressure Inlet Measurement Set-up" .
   2. Install the adaptor fitting from kit (J-46377) and washers in the fuel filter outlet line. Tighten fitting securely. See Figure "Fuel Filter Pressure Inlet Measurement Set-up" .

   Note: The adaptor fitting used is not a special tool and is not included in the Fuel Adaptor Parts Kit (J-46377) . The fitting can be ordered from Canton PDC under part number 915039012205.

   3. Perform the fuel pressure test at the fuel filter. Refer to "3.4.2 Performing Test #2 Fuel Pressure Test at the Fuel Filter" .

Section 3.4.2
Performing Test #2 Fuel Pressure Test at the Fuel Filter

Perform the following to test the fuel pressure at the fuel filter:‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.‪

1. Start the engine and warm it up to 80°-95°C (176°-203°F).
2. Measure and record the fuel pressure at two points: idle and rated speed.
3. Compare the recorded pressure reading with the specifications. If any of the readings are not within specifications, follow the proper troubleshooting steps. Refer to "3.4.3 Fuel Pressure Troubleshooting Procedures" .

   Description‪	Pressure — Bar (psi)‪
   Fuel Pressure at idle speed‪	2.0 (29)‪
   Fuel Pressure at rated speed‪	5.5–6.5 (80–94)‪
   Maximum difference between fuel filter inlet and fuel filter outlet pressure.‪	0.3 (4.0)‪

   Table 4. Fuel Filter Pressure Specifications
4. Remove the test equipment from the fuel filter.

Section 3.4.3
Fuel Pressure Troubleshooting Procedures

For fuel pressure tests results which were out of specification, check the following:‪

1. At idle rpm, with fuel pressure lower than 2 bar (29 psi) check the following:
   1. Check the pressure valve at the end of the fuel gallery. Look for opening pressure of 2 bar (29 psi).
   2. Check the fuel pump assembly (bearing and/or driven gear).
   3. Check to see if fuel system is drawing air.
2. At rated rpm, for fuel pressure lower than 5.5 bar (8.0 psi), check the following:
   1. Check the water separator filter condition.
   2. Check for restriction at the check valve on the MCM fuel heat exchanger.
   3. Check the main fuel filter for plugging, damaged seal allowing fuel flow from pressure side to the return side.
   4. Check for leaks at the suction lines from the fuel tank.
   5. Check the fuel pump assembly (bearing and/or driven gear).
   6. Check the fuel pump for damage or leaks.
   7. Check for restriction at the check valve on the fuel filter return line to the fuel tank.
3. At rated rpm, for fuel pressure higher than 6.5 bar (94.0 psi), check the following:
   1. Check the fuel return line and injector spill line for restrictions or bent lines.
   2. Check the fuel pressure valve for a blocked or restricted regulator orifice.