C7.1 Engines and Generator Sets Caterpillar

Engine Vibration Is Excessive

Usage:

C7.1 770

Refer to Systems Operation, Testing, and Adjusting for additional information on determining the cause of this condition.

Probable Causes

Driven equipment
Engine supports
Vibration damper
Low compression (cylinder pressure)
Electronic unit injectors
Individual malfunctioning cylinder

Recommended Actions

Note: When performing the following procedure, do not stand near the engine. The vibration may indicate an imminent component failure.

Note: Complete the procedure in the order in which the steps are listed.

Show/hide table

Table 1
Troubleshooting Test Steps	Values	Results
1. Driven Equipment A. Inspect the mounting bolts for the driven equipment. Inspect the alignment and the balance of the driven equipment. B. Inspect the coupling.	Driven equipment	Result The driven equipment and the alignment are not OK. Repair: Repair or replace the driven equipment. Result: The driven equipment and the alignment are OK. Proceed to Test Step 2.
2. Engine Supports A. Inspect the mounts and the brackets while the engine is operated through the speed range. Check for mounts and brackets that are loose and/or broken. B. Check the alignment of the mounts before operating the engine under load for any length of time.	Engine supports	Result: The mounts and brackets are loose and/or broken. Repair: Replace the mounts and brackets that are loose and/or broken. Result: The mounts and brackets are not loose and/or broken. Proceed to Test Step 3.
3. Inspect the Vibration Damper A. Clean any debris from around the vibration damper. Check the vibration damper for damage or leakage. B. Inspect the mounting bolts for damage and/or for wear. Refer to Disassembly and Assembly, "Vibration Damper and Pulley - Remove" and Disassembly and Assembly, "Vibration Damper and Pulley - Install".	Vibration damper	Result: The vibration damper or the mounting bolts are damaged. Repair: Replace the damaged vibration damper or the damaged mounting bolts. Result: The vibration damper and the mounting bolts are not damaged. Proceed to Test Step 4.
4. Low Compression (Cylinder Pressure) A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test".	Cylinder compression	Result: The results of the compression test are outside the specifications. Repair: Investigate the cause and rectify any faults. Note: Possible causes of low compression are shown in the following list: · Loose glow plugs · Faulty piston · Faulty piston rings · Worn cylinder bores · Worn valves · Faulty cylinder head gasket · Damaged cylinder head Result: The results of the compression test are OK. Proceed to Test Step 5.
5. Electronic Unit Injectors A. Use the electronic service tool to perform the automatic "Cylinder Cut Out Test". Note: If the compression test that was performed in Test Step 4 was satisfactory, the "Cylinder Cut Out Test" will identify any faulty injectors.	Electronic Unit Injectors	Result: A faulty injector is indicated. Repair: Remove any faulty electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove". Install new electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install". Repeat the automatic "Cylinder Cut Out Test". If the fault is still apparent, remove the replacement electronic unit injector and install the original electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove" and Disassembly and Assembly, "Electronic Unit Injector - Install". Result: All injectors are OK. Proceed to Test Step 6.
6. Individual Malfunctioning Cylinders A. With the engine speed at a fast idle, use the electronic service tool to perform the manual "Cylinder Cut Out Test". As each cylinder is cut out, listen for a change in the sound from the engine. When a cylinder is cut out, there should be a noticeable change in the sound of the engine. If a change in the sound of the engine is not noted, the isolated cylinder is not operating under normal conditions. If the isolation of a cylinder results in a change in the sound that is less noticeable, the cylinder may be operating below normal performance.	Cylinders	Result: The test indicates a faulty cylinder. Repair: Investigate the cause of the fault on any cylinder that is not operating. Investigate the cause of the fault on any cylinder that is operating below normal performance. Result: The test indicates that all cylinders are OK. Contact the Dealer Solutions Network (DSN).