Test compression pressure

AR01.00-W-1200A

Test compression pressure

25.06.2019

Engine

904.9 in model 374

Engine

904.9 in model 375, 673, 674, 676, 970, 972, 975, 976

Engine

904.904 in model 670

Engine

904.908/914/923/936 in model 668, 670

Engine

906.9 in model 374, 375, 950, 952, 953, 954

Engine

906.9 in model 957

except code MS8 (Natural gas engine)

Engine

906.9 in model 970, 972, 974, 975, 976

Shown on engine 904.9

1

Nozzle holder combination

2

Screw/bolt (up to engine end no. 046892)

3

Spherical washer (up to engine end no. 046892)

4

Screw/bolt with ball seat (as of engine end no. 046893)

5

Retaining clip

6.1

Connector

6.2

Retaining clip

7

Sealing ring

8.1

Compression pressure recorder

8.2

Diagram chart

8.3

Adapter

9

Constant throttle cap

10

Fuel return line

11

Circuit



Remove

1

Check valve clearance, adjust if necessary



Models 668, 670

AP05.30-D-0560A



Model 374.5, 375, 673, 674, 676, 950, 952, 953, 954, 957, 970, 972, 974, 975, 976

AP05.30-W-0560B

 For model 374.7 no maintenance manual was created.
Perform adjustment of valve clearance only when engine is cold or warmed up, at the earliest, 30 minutes after switching off the engine.

2

Warm up engine to normal operating temperature

3

Remove nozzle holder combinations (1)

Engine 904.9 up to engine end no. 040487

AR07.03-W-6831A

Engine 904.9 as of engine end no. 040488, engine 906.9

AR07.03-W-6831C



Check

 Danger

Risk of explosion caused by fuel igniting, risk of poisoning caused by inhaling and swallowing fuel as well as risk of injury to eyes and skin caused by contactwith fuel.

No fires, sparks, open flames or smoking. Pour fuels into suitable and appropriately marked containers only.
Wear protective clothing when handling fuel.

AS47.00-Z-0001-01A

4

Attach fuel return line (10) to unit pumps

AR07.15-W-2000-06A



Fuel return line of unit pumps for compression test

WF58.50-W-0700-02A

 Clamp

*000589403700

5

Tighten down connector (6.1) and retaining clip (6.2) using screw/bolt (2) or screw/bolt with radius seat (4)

 Stick sealing ring (7) to connector (6.1) with multipurpose grease.

 Bolt connecting retaining clip of nozzle holder combination to cylinder head

*BA07.15-N-1003-01A

Grease, silicone-based, 100 g

*BR00.45-Z-1008-06A

 Connector

*904589012100

6

Connect up compression recorder (8.1) with adapter (8.3) and connector (6.1)

 Connection of the compression recorder (8.1), refer to operating instructions from manufacturer.

 Compression tester

*001589782100

 Connector

*904589012100

7

Insert recording sheet (8.2) into compression recorder (8.1)

 Compression tester

*001589782100

 Warning

Risk of accident from vehicle starting off by itself when engine running. Risk of injury (bruises and burns) resulting from working on the engine while it is being started or when it is running.

Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.

AS00.00-Z-0005-01A

8

Crank engine using the starter (through simultaneously depressing engine start pushbutton switch and engine stop pushbutton switch)

9

Check remaining cylinders in the same way

10

Compare measurements on diagram chart (8.2) with the permissible values

Compression pressure at starter speed

*BE01.00-N-1001-01E

Permissible difference between individual cylinders

*BE01.00-N-1002-01E

 Compression tester

*001589782100

For deviations or further



checks, remove the cylinder head:

Models 668, 670

AR01.30-D-5800D

Model 374, 375, 673, 674, 676, 950, 952, 953, 954, 957, 970, 972, 974, 975, 976

AR01.30-W-5800A



Install

11

Remove compression recorder (8.1) and connector (6.1) together with sealing ring (7)

 Danger

Risk of explosion caused by fuel igniting, risk of poisoning caused by inhaling and swallowing fuel as well as risk of injury to eyes and skin caused by contactwith fuel.

No fires, sparks, open flames or smoking. Pour fuels into suitable and appropriately marked containers only.
Wear protective clothing when handling fuel.

AS47.00-Z-0001-01A

12

Remove fuel return line (10) on unit pumps

AR07.15-W-2000-06A

13

Install nozzle holder combinations (1)

Engine 904.9 up to engine end no. 040487

AR07.03-W-6831A

Engine 904.9 as of engine end no. 040488, engine 906.9

AR07.03-W-6831C

Check values for compression pressure

Number

Designation

ENGINE 902.9, 906.9 with CODE MS8 (natural gas engine)

ENGINE 904.9, ENGINE 906.9 except code MS8 (natural gas engine)

BE01.00-N-1001-01E

Compression pressure at starter speed

bar

15

28

Check values for compression pressure

Number

Designation

ENGINE 902.9, 906.9 with CODE MS8 (natural gas engine)

ENGINE 904.9, ENGINE 906.9 except code MS8 (natural gas engine)

BE01.00-N-1002-01E

Permissible difference between individual cylinders

bar

4

4

 Diesel injection system with unit pumps (MR/PLD)

Number

Designation

ENGINE 904.9, ENGINE 906.9 except CODE MS8

BA07.15-N-1003-01A

Bolt connecting retaining clip of nozzle holder combination to cylinder head

Hexagon socket

Nm

30

Twelve-point with radius seat

Nm

35

Repair materials

Number

Designation

Order number

BR00.45-Z-1008-06A

Grease, silicone-based, 100 g

A 001 989 28 51