MBE 900 DDEC VI Troubleshooting – Section 13.2 High Fuel Pressure

Section 13.2
High Fuel Pressure

To determine if high fuel pressure is causing a lack of power, perform the following steps:‪

1. Remove the fuel temperature sensor. See Figure "Disconnecting the Sensor" .
   

   1. Fuel Temperature Sensor‪

   2. Engine Wiring Harness‪

   Figure 1. Disconnecting the Sensor

2. Install the adaptor and banjo fitting, part of kit (J-46377) , and high pressure line (J-46372) . See Figure "Connecting the Adaptor" .
   

   1. Banjo Fitting‪

   2. Solenoid Unit Pump‪

   3. Adaptor from kit J-46377‪

   Figure 2. Connecting the Adaptor

3. Attach a calibrated gauge (J-46378) capable of reading 0-100 psi, to the high-pressure fuel line (J-46372) , leading to the tee-fitting. See Figure "Attaching the Calibrated Gauge" .
   

   1. Engine Trim Panel‪	3. Fuel Temperature Sensor‪
   2. Engine Wiring Harness‪

   Figure 3. Attaching the Calibrated Gauge

   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.‪

4. Start and run the engine to the speeds listed in Table "Fuel Pressure at Various Speeds" and record the fuel pressure.

   Engine Speed, rpm‪	Fuel Pressure, kPa (psi)‪
   600-650‪	430 (62)‪
   2500‪	400-650 (58-94)‪

   Table 5. Fuel Pressure at Various Speeds
5. Shut down the engine.
6. Remove the adaptor, banjo fitting, high pressure line, and high pressure gauge.
7. Reinstall the fuel temperature sensor.
8. Analyze the measure fuel pressure readings.
   1. If the fuel pressure is within specifications listed in Table "Fuel Pressure at Various Speeds" , check for high fuel temperature return; refer to "13.4 High Fuel Temperature Return" .
   2. If the fuel pressure is greater than specifications listed in Table "Fuel Pressure at Various Speeds" , refer to "13.3.1 Overflow Valve Replacement" .