sean.clarke Posted August 27, 2013 Share Posted August 27, 2013 Hi, one thing I keep forgetting to ask is if you guys notice that when you loosen/remove the fuel filler cap you get a huge rush of air. It is like there isn't a fuel tank breather, so when I fill up there is a small amount of air, I then use 3/4 of the tank and when I go to fuel up it is almost like there is a vacuum. I am surprised I have not spluttered to a halt, certainly on boats this can be an issue that would cause a breakdown (although the fuel tanks are much bigger so you would get a full on vacuum). Does anyone else experience this? Link to comment Share on other sites More sharing options...
vindiboy Posted August 28, 2013 Share Posted August 28, 2013 Yes I do and have on all my Ducatos. Link to comment Share on other sites More sharing options...
spospe Posted August 28, 2013 Share Posted August 28, 2013 Are you sure that what you are getting is a vacuum (less than atmospheric pressure) and not a slight pressure rise? i.e. is the air rushing out rather than in? Most cars that I have owned over the last 30 years have shown this effect, namely a slight rise in fuel tank pressure which manifests itself in an outgoing whoosh when opening the filler. This effect is quite normal and seems to be linked to the two-pipe fuel systems used today on fuel injection engines. This is where one pipe takes the fuel to the engine and the other returns unused fuel to the tank. The retuned fuel is warmer than the tank contents and this seems to cause a small pressure rise, hence the outgoing whoosh. If the vehicle where to be left overnight and then you opened the filler cap, probably there would not be any pressure. Link to comment Share on other sites More sharing options...
Guest peter Posted August 28, 2013 Share Posted August 28, 2013 It's normal, as there is no longer a tank breather, owing to anti pollution legislation. Link to comment Share on other sites More sharing options...
BrianBW Posted September 24, 2013 Share Posted September 24, 2013 Agree with all answers here, I too get the same phenomena. Glad to get a knowledgable reply! from Spospe Link to comment Share on other sites More sharing options...
Guest peter Posted September 24, 2013 Share Posted September 24, 2013 Yes and I was surprised myself. :D Link to comment Share on other sites More sharing options...
Tracker Posted September 24, 2013 Share Posted September 24, 2013 Air escapes from the tanks on all our vehicles both petrol and diesel when the tank cap is loosened thus confirming the higher air pressure within the tank than outside. Assuming it would be easy enough to engineer out, I have often wondered if it is designed to help maintain the flow of fuel to the fuel pump and injectors? Or something completely different - however there must be a reason - or maybe not and it is a 'characteristic'? Link to comment Share on other sites More sharing options...
sshortcircuit Posted September 24, 2013 Share Posted September 24, 2013 I am afraid my tank is a frooop, ingoing rather than a fusssh outgoing. I have always assumed that if you empty a space by drawing fuel then it has to be filled and that's what happens when the cap is taken off with an inrush of air. Need a real expert to sort oot this really worrying problem. Link to comment Share on other sites More sharing options...
mikebeaches Posted September 25, 2013 Share Posted September 25, 2013 Often get a 'whoosh' when removing the filler cap, and always assumed it was air rushing into the tank. But now I've read this thread, I'm not so sure which way the air is flowing?? *-) But at least I'm not alone - obviously in good company with other Ducato drivers. :-D Mike Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.