Workshop Hints

Before any service work is performed on any fuel system related component, always adhere to the following: 

• Observe relevant safety legislation pertaining to your area. 
• Ensure adequate ventilation. 
• Use exhaust extraction system where applicable (alleviate fumes). 
• DO NOT SMOKE while performing fuel system repairs. 
• Always wear adequate protection clothing including eye protection. 
• Use caution when working around a HOT engine compartment. 
• BMW does not recommend any UNAUTHORIZED MODIFICATIONS to the fuel system. The fuel systems are designed to comply with strict Federal Safety and Emissions Regulations. In the concern of product liability, it is unauthorized to sell or perform modifications to customer vehicles, particularly in safety related areas. 
• Always consult necessary REPAIR INSTRUCTIONS on the specific model you are working on before attempting a repair. 

The "CHECK ENGINE" Light  can be diagnosed with an aftermarket Scan Tool that allows Technicians without BMW Special Tools or Equipment to Diagnose an emission system failure.

Fig 1: Identifying Check Engine Light

Fuel Tank Vent Valve Noise is eliminated by placing an insulating mount (1) between the valve bracket and the mounting bracket and secured by a hex nut (2).

Fig 2: Identifying Hex Nut

Fig 3: Identifying Pinched Retainer Strap

Testing the Oxygen Sensor  should be performed using the DIS Oscilloscope from the "Preset Measurement" List. The scope pattern should appear as below for a normal operating pre-catalyst sensor.

If the signal remains low (rich condition) the following should be checked:

• Fuel Injectors 
• Fuel Pressure 
• Ignition System 
• Input Sensors that influence air/fuel mixture 
• Engine Mechanical 

If the signal remains high (lean condition) the following should be checked:

• Air/Vacuum Leaks 
• Fuel Pressure 
• Input Sensor that influence air/fuel mixture 
• Engine Mechanical 

Fig 4: Identifying Input Sensor Influence Air/Fuel Mixture