MALFUNCTION 1: Knock or tapping sound-(Continued)

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TM-9-2815-220-24 Maintenance Manual for AVDS-1790 2CA 2DA and 2DR Air-Cooled 12-Cylinder Diesel Engines

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MALFUNCTION 2: Diesel knock ("ping," usually at low-idle speed).

TM 9-2815-220-24

ENGINE NOISY OPERATION

0015 00

MALFUNCTION 1: (Continued)

Knock or tapping sound.

PROBABLE CAUSE

CORRECTIVE ACTION

a. (Continued) Rocker arm assembly

(1) (Continued) Locate faulty cylinder as

defective or out of adjustment.

follows:

PROCEDURE

OBSERVATION

ANALYSIS

Cylinder Compression Test Method:

Note cylinder with low pressure Indicates faulty cylinder,

Perform Cylinder

damaged rings, piston, valve,

(below 330 psi at 140-180

Compression Test

connecting rod or tight rocker arm

cranking rpm).

(WP 0033, Cylinder

(no valve clearance).

Compression Test).

PROBABLE CAUSE

CORRECTIVE ACTION

b. Excessive intake or exhaust valve clearance (1) Locate faulty cylinder as above.

or damage.

(2) Adjust valve clearance (WP 0034, Intake

and Exhaust Valve Clearance Adjustment).

c. Rocker arm assembly defective.

(1) Inspect, repair, or replace valve and/or

cylinder (WP 0133, Cylinder Assembly

Replacement).

(2) Replace rocker arm (WP 0104, Rocker Arm

Assembly and Cover Replacement).

d. Connecting rod, piston, ring damage, or

(1) Locate faulty cylinder as above.

loose piston pin.

(2) Check for damage (WP 0143, Connecting

Rod Assembly and Associated Parts Repair

and WP 0142, Pistons, Rings, and

Associated Parts Replace/Repair).

e. Crankshaft bearing damage.

(1) Check for damage (WP 0138, Crankshaft

Main Bearing Inspection).

f. Worn or damaged gears or bearings.

(1) Check for damage (WP 0178, Disassembly/

Assembly Procedure Sequence for the

AVDS 1790-2 Engine).

WP 0015 00-2