Member Since: 08 Apr 2013
Location: Pembrokeshire
Posts: 481
Where is the fuel tank vent?
On a D4.
Clearly , having replaced it, the fuel tank doesnt vent through the cap so im assuming there is one somewhere else.
Anyone know where?may the odds be ever in your favor
25th Mar 2019 9:12 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5053
Its not on the tank! Its on the filler neck
(Edit) There's one in the cap too!yµ (idµ - eAµ) ψ=mψ
25th Mar 2019 11:15 pm
chopcat
Member Since: 08 Apr 2013
Location: Pembrokeshire
Posts: 481
Thanks
Its really odd. I have replaced the cap but a still getting vacum in the tank which leads to fuel starvation . At least thats my diagnosis.
After 100 miles at motorway speeds i get fluctuating speed or hesitancy (difficult to describe) . Then stop open fuel cap, guegle gurgle, and then we are off ok again.
Its in for a service soon so will see what james french have to say on the matter.
Tcmay the odds be ever in your favor
27th Mar 2019 7:24 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5053
Can you actually hear escaping vacuum when you open the cap after a drive?
If so then clearly the cap is not doing its job. Gurgling noises might not necessarily be the same issue!yµ (idµ - eAµ) ψ=mψ
27th Mar 2019 3:04 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8235
Whenever I take the fuel cap off I can hear pressure coming out of the tank, not going in, I didn’t hear it on the D3.It can when others can't,
It will when others won't,
It goes where others don't.
27th Mar 2019 5:31 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5053
Pressure build up? that sounds a bit odd I'm sure you already know as the level in the tank is run down, the displaced fuel is replaced with an equal amount of air drawn in through the cap vent. I would have thought if there was for some reason a pressure build up, it would be depleted in the same way as a vacuum build up. (ie the vent) If you're sure there is pressure present rather than a vacuum, is it enough to pop the cap off when released? Just curious.yµ (idµ - eAµ) ψ=mψ
27th Mar 2019 6:06 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8235
No, but there is a positive hiss and that can be in the morning before the engine has started so it can’t be caused by heat, no other indiscretions or problems, it does it whenever I put fuel in, just like opening a can of coke.It can when others can't,
It will when others won't,
It goes where others don't.
27th Mar 2019 7:09 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5053
Ah that'l be carbonated diesel then yµ (idµ - eAµ) ψ=mψ
27th Mar 2019 7:36 pm
denny crane
Member Since: 29 Mar 2008
Location: Warwickshire
Posts: 147
As I recall, the vent pipe runs up the side of the fuel filler pipe.
See if it’s been pinched (as in compressed, not stolen lol)Owner of a 2010 Discovery 4 XS.
Plus a Mitsubishi Outlander (don’t ask...)
17th May 2019 2:52 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8235
chopcat wrote:
Thanks
Its really odd. I have replaced the cap but a still getting vacum in the tank which leads to fuel starvation . At least thats my diagnosis.
After 100 miles at motorway speeds i get fluctuating speed or hesitancy (difficult to describe) . Then stop open fuel cap, guegle gurgle, and then we are off ok again.
Its in for a service soon so will see what james french have to say on the matter.
Tc
Also a sign the fuel filter is partially blocked or non oem filter fitted. It can when others can't,
It will when others won't,
It goes where others don't.
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I'm sure you already know as the level in the tank is run down, the displaced fuel is replaced with an equal amount of air drawn in through the cap vent. I would have thought if there was for some reason a pressure build up, it would be depleted in the same way as a vacuum build up. (ie the vent) If you're sure there is pressure present rather than a vacuum, is it enough to pop the cap off when released? Just curious.
