drowning

G

Guest

Guest
You should not get the sucking noise, it is a vacuum in the tank. This
means that your tank breather is blocked. I once buckled a Peugeot 406
tank for this very reason.
Regards, Clive.
 
G

Guest

Guest
Clive
| You should not get the sucking noise, it is a vacuum in the
| tank. This means that your tank breather is blocked. I once
| buckled a Peugeot 406 tank for this very reason.
|
| Regards, Clive.
I asked this question about sucking noises a few years ago, and was told
(by the Ozzies) that it was normal and to start worrying only if I
*didn't* get it. So I investigated instead.
I found that if I drove up to a fuel pump and immediately unscrewed the
filler gap I had a mild vacuum in the tank, but that this dissipated in
a few minutes, and that the sucking noise was more pronounced if the
tank was nearly empty.
I found that the filler cap itself has a spring loaded air inlet, and a
bit of judicious sucking of the inside of the filler cap vent confirmed
two things:
(1) The pressure required to overcome the spring loading is very small,
and definitely not enough to buckle the tank.
(2) Low sulphur diesel doesn't taste any better than the older variety!
So in my experience a mild hissing is normal, and I rather suspect that
the tank breather underneath is designed to vent positive over-pressure,
and not to relieve a vacuum. I can see the sense in this, as it makes
you less likely to suck in water during deep wading. (The Ozzies didn't
explain why I should start worrying if the sucking noise stopped, but I
imagine this is what they meant.)
I suppose if you were worried you could take apart the filler cap and
wedge the spring-loaded flap open, but mine has been hissing at me for
five years now without any ill effects. Clearly the hissing is worse
when the tank is nearly empty as a larger volume of air needs to be
drawn in to equalise the pressures.
Would a partial vacuum affect the pump sucking up fuel, especially at
idle? I suppose so, but I would estimate the pressure required to open
the flap as a small fraction of a psi, and I'd have thought the effect
would be negligible. One could test this by unscrewing the filler cap
while idling and listening for a change of engine note.
Christopher Bell
Devon, UK
1996 1HD-FT

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G

Guest

Guest
The valve in the cap get get stuck, which is what happened to me - the
best test is to run with the cap loosley on or removed completely and
see if it makes a difference.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Skype: julianvoelcker
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
G

Guest

Guest
In my previous life, I sold Toyotas for 9 years and they all make the filler
cap hiss. Probably the most frequently asked question amongst new owners.
As for why, I don't know....
Neill Watson
On 27/6/06 10:05 am, "Christopher Bell" wrote:
 
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G

Guest

Guest
I have noticed most modern cars have a slight negative pressure when the cap
is taken off. Always wondered why there was more of a rush with an empty
tank, I think you right about that.
My guess is the slight negative pressure is an easy way of preventing fuel
fumes etc which the emissions people (and customers) don't like.
For reference bar, Head in water (m), psi
1 bar = 10 metres Head = 14.5 psi
So 1.5 psi pressure reduction in the tank is approx equal to 1 meter extra
lift?
Malcolm Bagley
Stafford, UK
1975 FJ45 Pickup (In Work)
_______________________________
-----Original Message-----
From: [Email address removed] [mailto:[Email address removed]] On
Behalf Of Christopher Bell
Sent: 27 June 2006 10:05
To: [Email address removed]
Subject: RE: [ELCO] drowning
Clive
| You should not get the sucking noise, it is a vacuum in the
| tank. This means that your tank breather is blocked. I once
| buckled a Peugeot 406 tank for this very reason.
|
| Regards, Clive.
I asked this question about sucking noises a few years ago, and was told
(by the Ozzies) that it was normal and to start worrying only if I
*didn't* get it. So I investigated instead.
I found that if I drove up to a fuel pump and immediately unscrewed the
filler gap I had a mild vacuum in the tank, but that this dissipated in
a few minutes, and that the sucking noise was more pronounced if the
tank was nearly empty.
I found that the filler cap itself has a spring loaded air inlet, and a
bit of judicious sucking of the inside of the filler cap vent confirmed
two things:
(1) The pressure required to overcome the spring loading is very small,
and definitely not enough to buckle the tank.
(2) Low sulphur diesel doesn't taste any better than the older variety!
So in my experience a mild hissing is normal, and I rather suspect that
the tank breather underneath is designed to vent positive over-pressure,
and not to relieve a vacuum. I can see the sense in this, as it makes
you less likely to suck in water during deep wading. (The Ozzies didn't
explain why I should start worrying if the sucking noise stopped, but I
imagine this is what they meant.)
I suppose if you were worried you could take apart the filler cap and
wedge the spring-loaded flap open, but mine has been hissing at me for
five years now without any ill effects. Clearly the hissing is worse
when the tank is nearly empty as a larger volume of air needs to be
drawn in to equalise the pressures.
Would a partial vacuum affect the pump sucking up fuel, especially at
idle? I suppose so, but I would estimate the pressure required to open
the flap as a small fraction of a psi, and I'd have thought the effect
would be negligible. One could test this by unscrewing the filler cap
while idling and listening for a change of engine note.
Christopher Bell
Devon, UK
1996 1HD-FT
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