Section 12.4
High Fuel Pressure

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

1. Remove the Supply Fuel Temperature Sensor (SFT Sensor) fitting from the fuel pump. see Figure "Supply Fuel Temperature Sensor" for SFT Sensor.
   

   1. Fuel Pump‪

   2. Fitting‪

   Figure 1. Supply Fuel Temperature Sensor

2. Attach a calibrated gauge capable of reading 0-517 kPa (0-75 psi) to the fuel pump.

   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.‪

   ENGINE EXHAUST ‪
   To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area. Engine exhaust is toxic.‪

3. Start and run the engine to the speeds listed in Table "Fuel Pressure (DDEC VI with Regulator)" and record the fuel pressure:

   Note: When checking fuel pressure, start the engine, run at the speeds listed in Table "Fuel Pressure (DDEC VI with Regulator)" , and record fuel pressure. Shut down the engine.

   Engine Speed, rpm ‪	Average Fuel Pressure, kPa (psi) ‪
   600‪	413 (60) ‪
   1200‪	413 (60) ‪
   1800‪	413 (60) ‪
   2100‪	413 (60)‪

   Table 4. Fuel Pressure (DDEC VI with Regulator)
4. Shut down the engine.
5. Remove the calibrated gauge from the fuel pump.
6. Reinstall the SFT Sensor, refer to the Series 60 Service manual (6SE2007), fuel system chapter.
7. Analyze the measured fuel pressure readings.
   1. If the fuel pressure is within specification listed in Table "Fuel Pressure (DDEC VI with Regulator)" , check for high fuel temperature return; refer to "12.5 High Fuel Temperature Return" .
   2. If the fuel pressure is greater than specifications listed in Table "Fuel Pressure (DDEC VI with Regulator)" , refer to "12.4.1 Fuel Pressure Regulator Replacement" .

Section 12.4.1
Fuel Pressure Regulator Replacement

Perform the following steps to replace the fuel regulator:‪

1. Remove the fuel pressure regulator; refer to appropriate service manual, fuel system chapter.
2. Install a new fuel pressure regulator; refer to appropriate service manual, fuel system chapter.
3. Verify new fuel pressure regulator replacement; refer to "12.4.1.1 Test the Engine with Replaced Fuel Pressure Regulator" .

Section 12.4.1.1
Test the Engine with Replaced Fuel Pressure Regulator

Perform the following steps to determine if the replaced fuel pressure regulator resolved lack of power condition:‪

1. Start and run the engine.
2. Run the engine at idle with a no-load for approximately 5 minutes, allowing the engine coolant to reach normal operating range.
3. Test drive the vehicle to ensure lack of power has been resolved.
   1. If no lack of power occurred during the test drive, no further troubleshooting is required. Shut down the engine.
   2. If lack of power occurred during the test drive, shut down the engine. Check for high fuel temperature return; refer to "12.5 High Fuel Temperature Return" .