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Whistle from Fuel filler area

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I have got a 1998 C2 and after a long drive I have notice a whistle from the fuel filler flap area, on short runs I've not noticed it do it. The idle is also affected and gets rough, if I take the filler cap off it stops the noise and the idle stabilises.

Ive done a search and no one seems to have posted a solution!

My thinking is it maybe the fuel pump going bad ? as I had one go on a boxster I had few years ago?

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Try research "EVAP system" for the car. It carries a charcoal cannister and series of valves and lines that capture fuel vapors from the system and route them into the intake to be burned. The system noramlly operates under vacuum, which is probably the source of the sound, although I'm surprised it has not thrown a code............

Edited by JFP in PA
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That is not normal and requires a valve in the fuel tank vent system to be replaced.

Do you know which valve it is and the part number ?

There are multiple valves in the system, you need to check for pending codes and do a little diagnostics to see what is up.


Edited by JFP in PA
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On a Boxster my sister-in-law had it was the fuel purge valve(name?) under the drivers side air intake.

PITA to get too -- we just jumpered it with a complete assembly from another Boxster.

whistle went away.

Prior to that I changed everything in the EVAP system.

I'm sure there is an equivalent on a 996 -- just not sure where.


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There is a purge valve (or actually maybe vacuum control valve) in the engine bay above the brake booster (near top of left hand side intake). Very easy to get to.

There is another valve near the EVAP canister, same place where it is on the boxster - behind the right front wheel (remove the wheel well liner to gain access).

Edited by logray
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Your car may or may not have all of these, but these are all the valves I could find related to fuel system.

These are all in the fuel tank/filler area:

#6, shut off valve in below diagram

#9, carbon canister valve in below diagram


#12, bleeder valve in below diagram

#21, tank vent valve in below diagram


This one is in the engine bay:

#30 fuel regeneration valve in this diagram:


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