Двигатели Scania четвёртой серии. Руководство - часть 237

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19

H7 - Checking the return fuel 

pressure

1 Connect pressure gauge 99 362 to the test 

connection on the return fuel manifold and 

open the test connection.

2 Turn the engine over using the starter 

motor. Read the pressure after 

approximately 20 seconds. The value 

should be below 0.8 bar.

3 If there is no detectable value after 

20 seconds, let the starter motor cool and 

repeat step 2.

Note: If there is air in the filter housing, 

pressure cannot build up. Vent the filter 

housing and try again.

4 Remove the pressure gauge and close the 

test connection.

H - Descriptions

20

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H8 - Checking the safety valve

!

WARNING!

The accumulator may be under high 

pressure. Reduce the pressure using 

SDP3 before starting work.
Wear protective goggles.

1 Remove the return pipe 2 from the safety 

valve 1 to the return fuel manifold 5.

2 Plug the connection in the return fuel 

manifold with cap nut 812 890 or 814 555 

and sealing plug 813 878.

3 Refit the return pipe at a slight angle to the 

engine. Connect a transparent hose 4 to a 

union 3 - 366 082 on the pipe. Pull the hose 

down into a can or similar.

4 Turn the engine over using the starter 

motor. If fuel leaks out of the safety valve, 

it is faulty and must be replaced.

5 Refit the engine pipes. Torque tighten.

H - Descriptions

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21

H9 - Renewing the cylinder head 

on the high pressure pump

!

WARNING!

The fuel system has a very high fuel 

pressure of up to 3,000 bars. The fuel 

system must be depressurised before 

any work is started. Use SDP3 to 

minimise the high pressure in the fuel 

system. 
A jet of fuel at high pressure can cut 

through the skin. 
The system should always be treated as 

pressurised, even when the engine is 

switched off.
Wear protective gloves and goggles.

IMPORTANT! The fuel system is very 

sensitive to dirt. It is therefore very important 

that everything is as clean as possible when 

work is carried out on the fuel system.

Do not use compressed air to blow components 

clean in the fuel system.

When cleaning, rags or paper which shed fibres 

must not be used. Use lint-free rags.

Clean tools before use.

Do not use worn chrome-plated tools as flakes 

of chrome may come off.

Plug or tape connections on components which 

have been removed.

IMPORTANT! A high pressure pipe that has 

been loosened or removed must never be 

refitted but must be replaced with a new one.

H - Descriptions

22

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1 Tilt the cab.
2 Remove the mudguard.
3 Clean around the fuel system.
4 Depressurise the fuel system. Use SDP3 to 

minimise the pressure. Place a rag over the 

high pressure pipe nut 1. Then undo the nut 

carefully.

5 Undo the cable connection.
6 Remove the high pressure pipe 2 and fit 

clean plugs in the fuel connections. 

Note: The high pressure pipe must not be 

reused.

7 Undo the banjo unions on the high pressure 

pump.

8 Remove the fuel return pipe 3 and plug the 

fuel manifold. Detach the pipes 4 and 5 

from the cylinder head.

9 Undo the cylinder head bolts alternately. 

Remove the cylinder head and gasket.

10 Remove the protective plugs on the new 

cylinder head. Fit new springs, a new 

gasket and new bolts.

Tightening torques

Cylinder head bolts

68 Nm

High pressure pump, banjo unions

55 Nm

High pressure pipe

38 Nm

Bracket for high pressure pipe

22 Nm

H - Descriptions