Series 50 – Section 25.2 High Fuel Pressure

Section 25.2
High Fuel Pressure

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

1. Remove either the fuel pressure sensor (FPS) or fuel temperature sensor (FTS) fitting from the secondary filter, if equipped; see Figure "Engine Fuel Pressure Sensor " for FPS, and see Figure "Engine Fuel Temperature Sensor" for FTS.
   

   Figure 1. Engine Fuel Pressure Sensor

   

   Figure 2. Engine Fuel Temperature Sensor

2. Install a tee fitting between the secondary filter and fuel outlet line.
3. Attach a calibrated gauge capable of reading 0-100 lb·in.² to the tee fitting.
4. Start and run the engine to the speeds, listed in Table "Fuel Pressure at Various Speeds" , and record the fuel pressure:

   Engine Speed ‪	Fuel Pressure ‪
   600 r/min‪	103-151 kPa (15-22 lb/in.2 )‪
   1200-1300 r/min‪	207-310 kPa (30-45 lb/in.2 )‪
   1800-2100 r/min‪	448-483 kPa (65-70 lb/in.2 )‪

   Table 1. Fuel Pressure at Various Speeds
5. Shut down the engine.
6. Remove the tee fitting and calibrated gauge from the secondary filter.
7. Reinstall the FTS, refer to "2.24.3 Installation of Fuel Temperature Sensor" or FPS sensors, refer to "2.23.3 Installation of Fuel Pressure Sensor" ; whichever was removed.
8. Analyze the measured fuel pressure readings.
   1. If the fuel oil pressure is within specification, listed in Table "Fuel Pressure at Various Speeds" , check for high fuel oil temperature return; refer to "25.3 High Fuel Oil Temperature Return" .
   2. If the fuel oil pressure is greater than specifications, listed in Table "Fuel Pressure at Various Speeds" , refer to "25.2.1 Restricted Fitting and Check Valve Replacement" .

Section 25.2.1
Restricted Fitting and Check Valve Replacement

Perform the following steps to replace the restricted fitting and check valve.‪

1. Remove the restricted fitting; refer to "2.8.2 Fuel Return System Check Valve" .
2. Install a new restricted fitting; refer to "2.8.4 Installation of PRO-CHEK ® Fuel System Check Valve" .
3. Remove the check valve; refer to OEM guidelines.
4. Install a new check valve; refer to OEM guidelines.
5. Verify check valve and restricted fitting replacement; refer to "25.2.1.1 Test the Engine with Replaced Check Valve and Restricted Fitting" .

Section 25.2.1.1
Test the Engine with Replaced Check Valve and Restricted Fitting

Perform the following to determine if the replaced check valve and restricted fitting 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 the engine down.
   2. If lack of power occurred during the test drive, shut the engine down. Check for high fuel oil temperature return; refer to "25.3 High Fuel Oil Temperature Return" .