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Bit of a long shot... petrol tank pressure
- Thread starter kowsmou
- Start date
The seals do deteriorate over time and indeed mine was an MOT advisory a few years ago, so changed it.
That said I doubt it has any relevance to your error code issues
That said I doubt it has any relevance to your error code issues
Not sure you get that vacuum anymore as air needs to get into tank otherwise petrol will struggle to reach engine. I have had that problem on another car where engine was struggling with a large vacuum from the tank and a new cap resolved the problem. There is probably a small pinhole in the cap somewhere.
You don't get any vacuum - the tank vents have one way valves to let air in but no vapours out. You may or may not develop a small positive pressure depending on ambient conditions and what temperature the fuel was when you filled up. The cap has a safety vent valve which triggers if the pressure gets too high.
A new petrol cap is a relatively cheap part so I’d say you’ve little to lose by trying that first.
As an aside, I learnt a bit about how evaporative emissions systems on modern engines work whilst supporting one of my customers, an Italian super car manufacturer, in my previous job. We were in the middle of an endurance test at Nardo when the car was brought back into the garage and then started to dump a recently filled tank of super unleaded onto the floor. Turns out that the emissions system periodically ‘sucks’ the vapour from the fuel tank into the engine inlet via a control valve operated by the engine ECU. For it to work the fuel cap has to be fully sealed. Turns out that there was a control map issue and this valve was opening too often during track testing and the prolonged vacuum imploded the fuel tank, causing it to split at a seam.
It is therefore quite possible that the ECU is measuring the ability of the system to draw a vacuum in the fuel tank when the valve is operated, and a fault code is thrown when it detects a leak to the outside world such as non fitted or defective fuel cap.
On the plus side of my story, my trip back to the airport after this truncated test in a crappy hire car was made brisker by a brimmed tank of hastily transferred super unleaded!
Chris
As an aside, I learnt a bit about how evaporative emissions systems on modern engines work whilst supporting one of my customers, an Italian super car manufacturer, in my previous job. We were in the middle of an endurance test at Nardo when the car was brought back into the garage and then started to dump a recently filled tank of super unleaded onto the floor. Turns out that the emissions system periodically ‘sucks’ the vapour from the fuel tank into the engine inlet via a control valve operated by the engine ECU. For it to work the fuel cap has to be fully sealed. Turns out that there was a control map issue and this valve was opening too often during track testing and the prolonged vacuum imploded the fuel tank, causing it to split at a seam.
It is therefore quite possible that the ECU is measuring the ability of the system to draw a vacuum in the fuel tank when the valve is operated, and a fault code is thrown when it detects a leak to the outside world such as non fitted or defective fuel cap.
On the plus side of my story, my trip back to the airport after this truncated test in a crappy hire car was made brisker by a brimmed tank of hastily transferred super unleaded!
Chris