B5.9G, B5.9LPG – Troubleshooting and Repair Manual – Engine Will Not Reach Rated Speed (RPM)

Verify the complaint

Test the engine operation while under load. Perform an engine acceleration test. Perform an engine load/install test. Refer to Procedure 014-002 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118. If engine has low or high power, refer to the Engine Power Output is Low or Engine Power Output is High symptom tree.

Electronic fault codes active or high counts of inactive fault codes

Refer to Section TF in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118, for fault code troubleshooting.

Throttle is not opening completely

Check for a blocked accelerator pedal or linkage. Use INSITE™ to verify that the throttle is opening to 85 percent or greater at full accelerator pedal. Refer to the INSITE™ User’s Manual, Bulletin 3885798.

Low or no fuel pressure at the mixer (secondary pressure)

Use an electronic service tool to measure the fuel pressure after the gas mass flow sensor and before the mixer. Refer to Procedure 005-047.

Low or no fuel pressure at the fuel filter (primary pressure)

Use an electronic service tool to measure the fuel pressure at the fuel filter. Refer to Procedure 005-061.

Electronic control module (ECM) calibration is malfunctioning

Verify the ECM calibration is correct. Check the calibration revision history for applicable fixes to the calibration stored in the ECM. Refer to the calibration history spreadsheet Click here to see ecm_calibration_rev_history.xls

on QuickServe® Online or the INCAL™ CD-ROM. Compare the calibration stored in the ECM with the engine rating and Control Parts List (CPL), Bulletin 4021326 or 4021327. If necessary, recalibrate the ECM. Refer to the appropriate electronic service tool manual and Procedure 019-032 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

Engine is operating above recommended altitude

Engine power decreases above recommended altitude. Refer to the Engine Data Sheet for specifications.

Fuel leak

Check the fuel lines, fuel connections, and fuel filters for leaks using the combustible gas detector service tool. Refer to Procedures 005-003, 005-047, and 005-052.

Keyswitch circuit is malfunctioning

Check the vehicle, equipment, or vessel keyswitch circuit. Refer to Procedure 019-064 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

Fuel control valve is malfunctioning

Check the fuel control valve for sticking or hysteresis. Refer to Procedure 019-102 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

Oxygen sensor offset parameter is not correct

Verify that the offset parameter on the oxygen sensor tag matches the oxygen sensor offset parameter listed in INSITE™. Refer to the INSITE™ User’s Manual, Bulletin 3885798.

Heated oxygen sensor is damaged or has drifted

Use INSITE™ to check for significantly improved engine performance with the system in open-loop operation. Refer to the INSITE™ User’s Manual, Bulletin 3885798.

Coil wire malfunctioning

Remove wire from engine and use a digital multimeter to measure resistance across the wire. Refer to Procedure 013-012.

Ignition coil malfunctioning

Check the ignition coil. Refer to Procedure 013-012.

Spark plug(s) damaged or incorrect gap

Inspect plug(s). Refer to Procedure 013-016.

Ignition system harness connector pins bent or damaged

Inspect harness. Refer to Procedure 019-196 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

Battery voltage is low or bad ground connection at battery

Check the batteries. Check the battery circuit. The battery cable ground must measure within OEM specifications for voltage drop under electrical load. Refer to Procedure 013-007.

Oil from the fuel has accumulated on the gas mass flow sensor, screen packs, or elsewhere in the fuel system

Check for oil in the fuel system. Refer to Procedure 005-009.

Turbocharger wastegate is stuck open

Inspect the wastegate for freedom of movement.

Air intake or exhaust leaks

Inspect the air intake and exhaust systems for air leaks. Refer to Procedure 010-024.

Charge air cooler is restricted or leaking

Inspect the charge air cooler for air restrictions or leaks. Refer to Procedure 010-027.

Air intake system restriction is above specification

Check the air intake system for restriction. Clean or replace the air filter and inlet piping as necessary. Refer to the Operation and Maintenance Manual, B5.9G, B5.9LPG, B Gas Plus, and B LPG Plus Engines, Bulletin 3666112, and the OEM service manual.

Exhaust system restriction is not within specification

Check the exhaust system for restrictions. Refer to Procedure 011-009.

Turbocharger is malfunctioning

Monitor the turbocharger boost pressure with an electronic service tool. Refer to the appropriate electronic service tool manual. Replace the turbocharger if necessary. Refer to Procedure 010-033.

Fuel grade is not correct for the application or the fuel quality is poor

Operate the engine from a tank of high-quality fuel. Refer to the Fuels for Cummins Engines, Bulletin 3379001, and the OEM service manual.

Intake manifold pressure sensor is malfunctioning

Check the intake manifold pressure sensor. Refer to Procedure 019-061 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

Drivetrain is not correctly matched to the engine

Check for correct gearing and drivetrain components. Refer to the OEM vehicle specifications.

Automatic transmission shift points are not set correctly

Verify that shift points are set at approximately 200 rpm below rated speed. Contact the transmission manufacturer.

Tachometer is not calibrated or is malfunctioning

Compare the tachometer reading with a handheld tachometer or an electronic service tool reading. Calibrate or replace the tachometer as necessary. Refer to the OEM service manual.