How to Solve Detroit Diesel GHG14 Engine Low Engine Compression

This diagnostic should only be performed after a manual compression test has been performed to ensure low engine compression is verified.


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1 Are all the actuator pistons on the engine brake rocker arms retracted (1)?

1a Yes; Go to step 2.

1b No; replace the engine brake rocker(s) that have a stuck actuator piston (2).

How to Solve Detroit Diesel GHG14 Engine Low Engine Compression

2 Check the camshaft timing.Camshaft Timing Verification. Do the camshaft timing marks line up per procedures?

2a Yes; Go to step 3.

2b No; correct engine/camshaft timing and verify repair.


3 Check valve lash and engine brake adjustments.

3a Yes; Go to step 4.

3b No; Go to step 5.


4 Conduct a Mechanical Cylinder Compression Test.Is compression within specification?

4a Yes; reassemble the engine and verify repairs.

4b No; Go to step 5.


5 Remove the cylinder head.

5a For the DD13, Removal of the DD13 Cylinder Head Assembly

5b For the DD15 and DD16, Removal of the DD15 and DD16 Cylinder Head Assembly


6 Inspect the cylinder head gasket for damage or exhaust leaks around the fire seals. Is the seal damaged or showing evidence of exhaust leaks?

6a Yes; measure the liner protrusion.

6b No; Go to step 7.


7 Inspect the following engine components:

7a Inspection of the Cylinder Head

7b Inspection of the Cylinder Liner

7c Further Analysis of the Cylinder Liner

7d Inspection of the Piston, Piston Rings and Connecting Rod

7e Inspection of the Intake and Exhaust Valves


8 If necessary, inspect the main bearings.

9 Has the cause of low compression been identified?

9a Yes; complete repairs, verify and release vehicle.

9b No; contact Detroit™ Customer Support Center at 800-445-1980.


More repair cases for Detroit Diesel engines,please refer to:Detroit Diesel Engine Repair

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