Friday, August 31, 2012

Fuel Vent Valve

This inexpensive valve that is mounted on the fuel tank may be the cause of failing fuel pumps and poor injector sprays and may even cause bad fuel consumption with the combined effects experienced.

W124/W201 Fuel Vent Valve
Part number
A 201 476 02 32

The purpose of this valve is to allow air to flow into the fuel tank when there is a vacuum of certain pressure that has built up within the fuel tank.

The vacuum is created when fuel level starts to drop [ going out via the fuel pump and to the injectors within the engine's cylinders ]. Assuming the fuel tank cap is working proper, the tank should be air tight and if the volume of fuel decreases without compensating for the reduction of fuel volume within the tank, a vacuum will be created.

Imagine the vacuum pulling the fuel back to the tank when the fuel pump is trying hard to push it to the injectors. The fuel vent valve ensures that external air is allowed in once the vacuum inside reaches a certain threshold.

A symptom to look out for will be loud air gushing sounds whenever the fuel cap is opened for refuelling at the gas stations.

At most local Singapore stockists for less than S$30, this is an inexpensive restoration that might have the most benefits. Installation of the item can be done quite swiftly at your preferred workshop.

Actual location of how it goes into the fuel tank can be found at this site [ Item 71 on the diagram]

If for any reasons, the part is not available in your region, it is recommended to release the vacuum pressure, by opening and closing the refuelling cap, before you begin a new trip on your W124/W201.

Credits to Mr TPH for finding out the cause of his loud whirring fuel pump and going through several new fuel pumps while damaging a fuel distributor along the process before discovering it was this little bugger that needed replacement