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