Fuel tank vacuum
Discussion
Hi,
Just returned from a fairly spirited hour and a half drive and, when I turned the engine off, I could hear a hissing noise, quickly tracked down to the fuel filler cap. When I undid it, there was a whoosh as air was drawn in and the tank popped. I seem to recall a thread on the subject but 'search' turned up nothing. Any ideas, my Griffing chums??
Just returned from a fairly spirited hour and a half drive and, when I turned the engine off, I could hear a hissing noise, quickly tracked down to the fuel filler cap. When I undid it, there was a whoosh as air was drawn in and the tank popped. I seem to recall a thread on the subject but 'search' turned up nothing. Any ideas, my Griffing chums??
I believe you have a 500 with the carbon cannister up front, have a look at this to give you an idea of the system:
http://www.bertram-hill.com/replacing-the-fuel-lin...
The fuel filler cap should be sealed (not on early cars) and the tank breathes via a roll over valve next to the tank filler which feeds a long rubber hose from the filler neck to the carbon cannister
The cannister is connected to the plenum via a purge valve. When the engine is up to temperature the ECU sends a signal to open the purge valve and allows the cannister to vent into the plenum to clear out the petrol fumes.
Possible cause of a vacuum: Roll over valve stuck closed, Your cannister is blocked, the hose connecting it to the tank filler neck kinked or the purge valve not working.
The cannister is hidden away at the offside inner wing behind a silicon sealed panel.
You could try disconnecting the rubber hose from the filler neck and blowing down it to see if it is free.
http://www.bertram-hill.com/replacing-the-fuel-lin...
The fuel filler cap should be sealed (not on early cars) and the tank breathes via a roll over valve next to the tank filler which feeds a long rubber hose from the filler neck to the carbon cannister
The cannister is connected to the plenum via a purge valve. When the engine is up to temperature the ECU sends a signal to open the purge valve and allows the cannister to vent into the plenum to clear out the petrol fumes.
Possible cause of a vacuum: Roll over valve stuck closed, Your cannister is blocked, the hose connecting it to the tank filler neck kinked or the purge valve not working.
The cannister is hidden away at the offside inner wing behind a silicon sealed panel.
You could try disconnecting the rubber hose from the filler neck and blowing down it to see if it is free.
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