Troubleshooting Boost Pressure Below Normal Boost Pressure Below Normal
The probable root causes are listed below: Air inlet restrictio restrictions ns Fuel supply Injector solenoid Wastegate Engine speed/timing signal Low fueling rate Active Active engine derate Intermittent sensor problem Perform the following checks: 1. Check for restrictions in the air inlet system. Refer to Systems Operation, "Restriction of Air Inlet and Exhaust" E xhaust".. 2. Check Check fuel li nes for the following problems: restr restrictions, ictions, collapse collapse and pinched p inched lin e. Repair the lines and/or replace replace the lines. Refer to Testing and Adjusting, "Fuel System Inspection". a. Check Check the fuel tank for foreign foreign objects which may block the fuel suppl y. Check for air air in the low pressure fuel supply system after you have performed the following procedures: Replace the filters. Work on the low pressure fuel supply circuit Replace the fuel injectors. b. Purge air from from the low low pressure pressure fuel supply suppl y circuit circuit with the hand priming p ump and by cranking the engine in 30 second cycles. After you crank the engine, stop for two minutes. This will allow the starting motor to cool. Loosen the vent plug at the fuel return. The plug is located on the rear upper left side of the engine block. Hand prime the engine again if air in fuel continues. A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel. c. Check Check fuel quality. q uality. In temperatures temperatures below 0 °C (32 °F), check check for solidifi solidified ed fuel (wax). ( wax). Refer to Special Special Publication, SEBD0717, "Diesel Fuels And Your Engine". Check the fuel pressure while the engine is cranking. Check the fuel pressure at the filter. Refer to the Specifications manual for correct pressure values. If the pressure is low, check for plugged fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Check for a problem with the combustion system. 3. Check for active diagnostic di agnostic codes for for the injector solenoids. Check Ch eck for logged logg ed di agnostic codes for for the injector solenoids. Perform the Injector Solenoid Test. Observe that the injector solenoids are being energized on the Caterpillar Electronic Technician (ET). Perform the Cylinder Cutout Test. Locate the misfiring cylinder. Refer to the diagnostic functional test Troubleshooting, "Injector Solenoids".
4. Verify that the exhaust byp ass valve for the wastegate can close. Use Cat ET to override the wastegate to 0 percent. Perform a torque converter stall test. After 15 seconds, a High Boost Pressure Event should result. If a High Boost Pressure Event occurs, the wastegate is closing properly. 5. Check Cat ET for the following l ogged Diagnostic Codes 190-02 and 190-08. Refer to the diagnostic functional test Troubleshooting, "Engine Speed/Timing Sensor". 6. Check the fueli ng rate. Refer to Specifications Manual. If the fuel rate is low, complete the cylinder cutout test. 7. Connect Cat ET and check for "ACTIVE" engine derates. If the active engine derate is due to "Axle Protection", refer to the Service Manual for the transmission or implement control. Perform the torque converter stall test. Compare the achieved stall speed to specifications. If the output meets specifications, continue with diagnostic checks. 8. Check for any recently logged diagnostic codes. Check the connectors and wiring for any signs of damage. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors". POSTED BY MECHANIC TRADE SPECIALIST AT 11:31 AM LABELS: TROUBLESHOOTING BOOST PRESSURE BELOW NORMAL
