Test compression pressure

AR01.00-B-1200A

Test compression pressure

12.02.16



Check

Danger!

Risk of accidents due to vehicle moving when the engine is started. Risk of injuries by pinching or suffer burns when working while the engine started or when the vehicle is moving

Assure vehicle against unintentional move. Use tight fitting and closed work clothes. Do not touch heated or running parts.

AS00.00-B-0005-01A



The measurement of compression pressure aims at obtaining a diagnose of the engine situation in the cases of:

Cylinders with excessive wear;

Valve leakage;

Damaged pistons or piston rings;

Burnt cylinder head gasket.

1

Check and if necessary adjust valve clearance

 To measure the compression it is necessary that the valves are adjusted.

AP05.30-B-0560F

2

Run the engine until service temperature is reached and stop it next

*BE20.10-B-1001-02A

3

Remove the head cover

Cover with direct vent.

AR01.20-B-5014C

Cover with crankcase pressure regulating valve.

AR01.20-B-5014D

4

On cylinder head, slacken the nuts fastening the injection lines

 Be careful and avoid bending the injection lines.

AR07.11-B-9230A

5

Loosen the injection nozzle carriers, the injection lines and displace them to a side

AR07.11-B-9230A

6

Remove the return flow line from the injection nozzle carriers

AR07.11-B-9230A

7

Liftoff al injection nozzle carriers

AR07.03-B-6831C

8

Detach the acceleration rod or cable at the injection pump and displace it to the stopped position

9

Actuating the starter, crank the engine for 5 seconds

 In this operation, eventual combustion residue is expelled from inside the cylinder.

10

Install the adapter in place of the injection nozzle carrier and connect the compression gauge

 Adapter

*352589002100

 Compression recorder

*001589782100

11

Crank the engine through the starter until the compression reading in the recorder stabilizes

 Crank at least 8 engine turns.

12

Relieve the pressure (bleed) in the compression recorder after each measuring

 If the compression pressure reading is equal or above the minimum permissible pressure and the pressure variance between cylinders is below the maximum permissible, the engine will be in good condition.

Minimum permissible compression pressure.

*BE01.00-B-1001-01A

Maximum pressure variance between cylinders.

*BE01.00-B-1002-01A

If the obtained value is below the minimum permissible, search its cause:



13

Pour some 30 ml engine oil in the cylinder, crank the engine (3 to 5 turns) and repeat the compression measuring

 Should the compression pressure increase, one can conclude that the cause of low pressure is due to problems related to piston rings.

If the compression pressure does not increase, the cause may be due to problems with the gasket, valves, or burnt seats or still, damaged piston or cylinder.

14

Repeat the measuring in the remaining cylinders

15

Install the injection nozzle holders.

AR07.03-B-6831C

16

Connect the injection and return lines

AR07.11-B-9230A

17

Connect the acceleration rod or acceleration cable to the injection pump

18

Install the valve cover on engine

 Cover with direct vent.

AR01.20-B-5014C

 Cover with crankcase pressure regulating valve.

AR01.20-B-5014D

Número

Denominação

Engine 372.9, 374.9, 376.9 (except for gas engines), 377.9, 386.9

BE01.00-B-1001-01A

Minimum admissible compression pressure (at sea level)

bar

20

BE01.00-B-1002-01A

Maximum variation between an engine's cylinders

bar

4

Número

Denominação

Engine 374.905/907/908, 374.950/951/952, 374.953/978/979, 3749.985/986/987, 3749.988/989/990 Engine 374.976/977/992 from engine number 674.464 on

Engine 372.9, 376.90/93/94, 376.95/98/99

BE20.10-B-1001-02A

Nominal temperature and start of opening

Nominal

°C

83

83

Beginning of opening

°C

81...85

81...85

Número

Denominação

Engine 377.9 except for 377.987;

Engine 376.961/962/963, 376.964/967/972

BE20.10-B-1001-02A

Nominal temperature and start of opening

Nominal

°C

83

83

Beginning of opening

°C

81...85

81...85

Número

Denominação

Engine 374.991/993/996 Engine 374.976/977/992 up to engine 674464Engine 377.987

Engine 372.924/926/927, 376.929 Engine 374.980/981/982, 374.984 Engine 376.919/922/923, 376.924/925/926, 376.927/968/969, 376.970/975/976, 376.977

BE20.10-B-1001-02A

Nominal temperature and start of opening

Nominal

°C

86

79

Beginning of opening

°C

84...86

77...81

Número

Denominação

386.9

BE20.10-B-1001-02A

Nominal temperature and start of opening

Nominal

°C

71

Beginning of opening

°C

69...73