6.7L Cummins Troubleshooting – Engine Cranks Slowly – (Electric Starter)

Batteries are cold

Check the battery heater. Refer to the OEM service manual.

Electronic fault codes active or high counts of inactive fault codes

Read the fault codes with an electronic service tool. Refer to Section TF in Troubleshooting and
Repair Manual, CM2150 Electronic Control System, ISB, ISC, ISL, ISLe, ISDe, and QSB3.3
Engines, Bulletin 4021570.

Battery voltage is low

Check the batteries and the unswitched battery supply circuit. Refer to Procedure 013-007 in
Section 13.

Broken, loose, or corroded starting circuit connections

Inspect, clean, and tighten both the positive and negative connections between the starting motor
and battery, including the magnetic switch. Refer to Procedure 013-009 in Section 13.

Battery capacity is below specification

Refer to Procedure 013-007 in Section 13. Replace the batteries if necessary.

OEM starter interlock devices engaged

Check the starter interlock devices. Refer to the OEM service manual.

Lubricating oil pressure switch, gauge, or sensor is malfunctioning or is not in the correct location

Check the oil pressure switch, gauge, or sensor for correct operation and location. Refer to the OEM
service manual.

Battery cables are not the correct gauge or length

Replace the battery cables with larger gauge or shorter length cables. Refer to the OEM service
manual.

Engine-driven units are engaged

Disengage engine-driven units.

Starting circuit component is malfunctioning

Check the starting circuit components. Refer to the OEM service manual

Starter motor malfunction

Check the voltage drop at the starti ng motor. Refer to Procedure 013-020 in Section 13.

Starting motor pinion or ring gear is damaged

Remove the starting motor, and inspect the gear. Refer to Procedure 013-020 in Section 13.

Lubricating oil level is above specification

Check the oil level. Verify the dipstick calibration and oil pan capacity. Fill the system to the specified level. Refer to Procedure 007-009 in Section 7.

Lubricating oil does not meet specifications for operating conditions

Change the oil and filters. Refer to Procedure 018-003 in Section V. This procedure can be found
in the Operation and Maintenance Manual, ISB CM2150 , Bulletin 4021602 and the Owners
Manual, ISB CM2150, Bulletin 4021601, to verify the correct lubricating oil is being used.

Crankshaft rotation is impaired

Check the crankshaft for ease of rotation. Refer to Procedure 001-016 in Section 1.

Internal engine damage

Analyze the oil and inspect the filters to locate an area of probable damage. Refer to Procedure
007-083 in Section 7.