Fuel System - Tapping/Knocking Noise

CATEGORY
Engine

SECTION
2

PAGE
13

ISSUE
10/91-0145

CODE
241

Subject:
Fuel Pulsation Noise

Application:
M9O- 9000 Models with B234 Engine

Some 1990- 9000 vehicles equipped with the 2.3 liter engine may develop a pulsation noise that can be heard inside the car. Customer complaints often refer to a tapping or knocking sound that is heard when the car is idling at a stop.

The most likely cause of this noise is a faulty fuel line damper, located between the fuel supply line and the distribution rail on the engine. The function of this damper is to reduce the fuel pressure waves that are generated in the supply line by the simultaneous opening and closing of all four injectors. All cars have the noise to some degree, but it may be objectionable to some customers, particularly if the diaphragm within the damper is damaged.





A new damper, P/N 41 64 232, containing a spring-loaded diaphragm has been developed for use as a service measure. A modified version of this damper will also be introduced as a running change during mid-1992 production.

Parts required:

Damper P/N 41 64 232

Seal rings (2 required) P/N 89 81 979

Repair procedure:

1. Disconnect the negative cable from the battery.

WARNING!

Always observe the following safety precautions when working on the fuel system

^ No Smoking!

^ Have A Fire Extinguisher Nearby.

^ Wear Eye Protection.

^ Work In A Well Ventilated Area (Use Vapor Extraction Equipment If Available.)

^ Avoid Prolonged Skin Contact With Fuel And Wear Suitable Gloves.

2. Carefully loosen the fittings securing the damper to the supply line and distribution rail. Use shop rags to soak up any fuel that leaks out.

3. Remove the old fuel damper.

4. Install the new damper using new seal rings. Dry off any fuel leaked during installation.

5. Reconnect the negative battery cable to the battery.

6. Start the engine and check carefully for any signs of leaks or seepage.

Warranty information:

For warranty claims, use Failure Coding 24143-40-0-01-01. Time allowance is Labor Operation No. 24143 (0.2 hour).