Evaporative System Troubleshooting - BMW 5251 Service Manual

Fuel Tank and Fuel Pump
Evaporative system troubleshooting
-
Start by accessing diagnostic trouble codes (DTCs) using a
BMW or BMW compatible aftermarket scan tool.
For purposes of OBD II emissions compliance, the DME
system sets a diagnostic trouble code (DTC) when it de-
tects a leak that is equal or larger than minimum lealc
sensed by system.
Malfunction Indicator Light (MIL) is illuminated upon sec-
ond recurrence of fault. See OBD On-Board Diagnostics.
-
When leak testing, observe following conditions to obtain
plausible results:
Fuel tank ' 1 , to
' I .,
full.
0
Vehicle parked for at least 2 hours to allow fuel to reach
room temperature. Ideal fuel temperature is 10"- 20°C
(50"
-
68" F).
Do not refuel immediately before lealc test.
-
If a leak is detected, check the following areas:
* Fuel filter cap (leaking or off).
Fuel tank ventilation lines leaking at fuel tank or activated
carbon canister.
i
Tank ventilation valve leaking (in engine compartment).
Fuel level sensorlfuel pump cap leaking.
Evaporative system component replacement is covered later
in t h ~ s group in Fuel Tank and Fuel Lines.