Fresh Air Valve

[bmx672]

The issue: I am unable to fill the tank past half.

The reed switch (magnetic switch attached to filler tube) was not activating the vent valve for the gas tank. The gas pump nozzle flips the little cover open and the cover engages the reed switch (magnetically). Thus sending everything in motion for the tank to vent while filling.
(I checked all the obvious issues, fuses, the tank, sending unit, obstructed spit back valve in the neck etc etc.)
My next steps were to check continuity and power to all the switches and valves. Everything looked good and worked when power was applied separately. But when everything was connected... nothing!
Next step... to look at the wire diagram in the Bentley. On that same system of wires is the "Fresh Air Valve" my guess is that when fueling up the car shuts off outside venting to avoid pulling fumes into the cabin. There has to be a short there at that connection because when we cut that wire and used a different configuration the filler flap activated the reed switch and the vent valve opened for the fuel tank! Everything worked when we eliminated the "Fresh Air Valve" from the daisy chain. So therein lies the problem I believe.
My next step is to see if the "Fresh Air Valve" works... if not maybe theres just corrosion where the wires split? Not sure...

[insite]

what year is your car?

[bmx672]

It's a 2000...

[insite]

ok, this is not intuitive at all. the voltage supply block is actually in the trunk. it supplies:

1. mass air sensor
2. varioRAM actuator
3. secondary air injection valve
4. tank venting valve
5. DME relay KL.87
6. camshaft adjustment actuators

the junction block is located in grid position 15cN, which is highlighted in red below. the point is called terminal 30.

[bmx672]

THANKS Insite! I cant wait to get back into the car tonight and see what I can find! I'll let you know!

Thanks again!

[bmx672]

Insite, would you know where terminal VS.24 is located? That's the tie in for the reed switch, tank vent valve and the fresh air valve in the Bentley wire diagram. We think that's the location where the problem might be. But i have no idea where VS.24 is. You had mentioned that it could be on the climatronic. Would they tie in at the location in the trunk on the diagram you supplied? Not sure if you know but any help would be greatly appreciated.
Thanks!

[Dale_K]

I don't know the terminology of "fresh air valve". But it might be one of the pair of valves behind the right headlight. I know you're already working in that area and don't want to lead you astray. One of them definitely leads to the atmosphere and I thought it was the one that let fresh air into the tank during driving. If one of those valves is drawing down the circuit at a time when they're supposed to work together you might get a situation where the other valve works OK when the bad valve is disconnected.

Truth is I don't know. Hope the magnetic switch helps you.