Fuel System - Incorrect Fuel Flow, Poor Driveability

SECTION:
2

GROUP:
23

NO.:
824

DATE
July 1996

Replacing pulsation damper 850 1997-

REFERENCE: TP 2318201, SECTION 2(23, 28), ENGINE MANAGEMENT SYSTEM MOTRONIC 4.4; 850 (B5254T) 1997.

Replacing pulsation damper

A pulsation damper P/N 1275658-1 to damp shock waves in the fuel injection system has been introduced on the following engine variants: B5254T and B5254S.

Special tools: 999 5533-B (4), 999 5620-3 (1)

WARNING!
Do not smoke or have anything in the area which can ignite or cause sparks.

AA1

The pulsation damper P/N 1275658-1 reduces the shock waves in the fuel rail when the injectors open and close.

These shock waves can produce the incorrect fuel flow at certain engine speeds.

A faulty pulsation damper can affect driveability and diagnostic trouble codes (DTCs) can be stored if the car is driven with a faulty pulsation damper.

The fault may also affect the heated oxygen sensors (HO2S).

The pulsation damper is made up of a diaphragm acting on a spring.

AA2

Drain fuel injection system





Drain the fuel injection system before replacing pulsation dampers.

- Drain fuel system according to: Refer to section 2 (23, 28), Draining fuel system.

Remember the fire risk and observe strict cleanliness when working on components in the fuel injection system.

Position paper wipe to absorb fuel spills.

AA3

Removing

Remove:

- fuel rail cover.

- injector connectors.

- fuel line clips.

AA4

Installing holders

Install:








- 4 holders 999 5533-8 and 1 holder 999 5620-3 on the injectors. Position holder 999 5620-3 closest to the fuel pressure line, refer to the left holder (A) on the illustration.

- press in holder to ensure that it is seated firmly against the injector.

- screw down adjustment screw so that the contact plate is in contact with the fuel rail, turn the screw another half turn.

AA5

Removing fuel rail

Remove:

- screws holding fuel rail. Lift fuel rail with injectors.

- remove fuel rail from fuel line by twisting it approx. 90° and pulling it away from the fuel line. Place paper wipe under the connector to absorb fuel spills.

Note!
Handle injectors carefully to avoid damage to nozzles and needles.

AA6

Removing pulsation damper





Remove:

- screws holding mounting rail to fuel rail.

- mounting rail.

- pulsation damper.

AA7





Installing new pulsation damper

- Lubricate the new pulsation damper 0-ring with a thin layer of petroleum jelly.

- Install the new pulsation damper.

- Remove holders from all injectors.

- Install mounting rail. Pull injector nozzles out a few millimeters from the fuel rail to install mounting rail.

- Tighten mounting rail on fuel rail.

AA8

Installing





Install:

- fuel rail on intake manifold.

- new screws and tighten to 10 Nm (7.4 ft.lbs).

- fuel line clips.

- injector connectors. Check that each connector is fitted with a rubber seal.

- fuel rail cover. Start engine and check for fuel leakage.

WARRANTY STATEMENT: Claims may be submitted under the New Car Limited Warranty when a manufacturing defect is present using claim type: O1

Operation No. Labor description Time allowance

23713-3 Pulsation damper, replace 0.4 hr