[Sorry if you get this, or similar, twice - I one earlier and I think
it failed - that'll teach me to use Google Groups!]

I got a call from my neighbour today advising me that my girlfriends
car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler
cap.

I couldn't get my head around how this could be, not unless she'd
filled it right to the brim (it had been filled only at the weekend)
and perhaps today's sunshine had increased the pressure such that it
was now overflowing (to the tune of a drip every few seconds). But
then it would really take some doing to fill it that much... right?

So, when I got home I removed the filler cap and indeed found the
petrol level to be right at the top... I wondered if the camber of the
road had anything to do with it so replaced the cap and drove to a
flat spot. When I got there I checked again and the level had dropped
(completely out of sight in fact) and so I returned to the original
parking position... and the petrol was still nowhere to be seen.

I wondered if perhaps something had blocked the filler pipe and
managed to keep the level high? And perhaps this blockage was now in
the tank? But then surely this would have posed difficulties when she
filled it... and the receipt shows a full tank (~30L) was I'm not so
sure about the theory anymore...

I'm now thinking more along the lines of a trapped air bubble? (I
notice the filler pipe travels vertically down from the opening for
around 8" and then horizontally for perhaps 20" to the tank. There
appears to be two pipes to the filler - I don't know where the other
goes (/comes from).

Any ideas? I'm losing hair scratching my head on this one so your
thoughts would be much appreciated!

Incidentally, for what it's worth, the filler cap is a lockable
aftermarket affair - when we bought the car a few years ago the cap
was found to be one of those temporary push-in affairs. Also, we
occasionally smell petrol inside the car (in the boot mainly, near the
filler) and this is usually shortly after filling the tank. I've
always put this down to sloshing fuel in the tank/filler and the
likely less-than-perfect fitting of the aftermarket cap (whose gasket
I see is starting to perish) which might be letting the occasional
splash out to the surrounding area.

Mathew

Mathew Newton wrote:
> [Sorry if you get this, or similar, twice - I one earlier and I think
> it failed - that'll teach me to use Google Groups!]
>
> I got a call from my neighbour today advising me that my girlfriends
> car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler
> cap.
>
> I couldn't get my head around how this could be, not unless she'd
> filled it right to the brim (it had been filled only at the weekend)
> and perhaps today's sunshine had increased the pressure such that it
> was now overflowing (to the tune of a drip every few seconds). But
> then it would really take some doing to fill it that much... right?
>
> So, when I got home I removed the filler cap and indeed found the
> petrol level to be right at the top... I wondered if the camber of the
> road had anything to do with it so replaced the cap and drove to a
> flat spot. When I got there I checked again and the level had dropped
> (completely out of sight in fact) and so I returned to the original
> parking position... and the petrol was still nowhere to be seen.
>
> I wondered if perhaps something had blocked the filler pipe and
> managed to keep the level high? And perhaps this blockage was now in
> the tank? But then surely this would have posed difficulties when she
> filled it... and the receipt shows a full tank (~30L) was I'm not so
> sure about the theory anymore...
>
> I'm now thinking more along the lines of a trapped air bubble? (I
> notice the filler pipe travels vertically down from the opening for
> around 8" and then horizontally for perhaps 20" to the tank. There
> appears to be two pipes to the filler - I don't know where the other
> goes (/comes from).
>
> Any ideas? I'm losing hair scratching my head on this one so your
> thoughts would be much appreciated!
>
> Incidentally, for what it's worth, the filler cap is a lockable
> aftermarket affair - when we bought the car a few years ago the cap
> was found to be one of those temporary push-in affairs. Also, we
> occasionally smell petrol inside the car (in the boot mainly, near the
> filler) and this is usually shortly after filling the tank. I've
> always put this down to sloshing fuel in the tank/filler and the
> likely less-than-perfect fitting of the aftermarket cap (whose gasket
> I see is starting to perish) which might be letting the occasional
> splash out to the surrounding area.
>
> Mathew

first off get a genuine cap

On Sep 18, 8:13 pm, "Mrcheerful"  wrote:

> first off get a genuine cap

Do you think that caused it? (or is it just a sensible step?)

I'm thinking the aftermarket cap might just be a coincidence (of
course, this might the down to having read somewhere that the genuine
article is something like £54 and will come with a big fat Ford
key...!)

Mathew

Mathew Newton wrote:
> On Sep 18, 8:13 pm, "Mrcheerful"  wrote:
>
>> first off get a genuine cap
>
> Do you think that caused it? (or is it just a sensible step?)
>
> I'm thinking the aftermarket cap might just be a coincidence (of
> course, this might the down to having read somewhere that the genuine
> article is something like £54 and will come with a big fat Ford
> key...!)
>
> Mathew

they are not that dear, maybe 20 quid or therabouts.  but if the aftermarket 
one does not breathe as it should ............  Worth changing, even if you 
get one from a breakers.  other possibles might be something in the pipe, 
but I doubt it.
If the tank was very full, parked to one side with fuel up the filler pipe, 
when the air above the fuel in the tank expands (as it always does, because 
fuel from an underground tank is much colder than above ground) it will then 
push the 'plug' of fuel further up the filler pipe, the cap is the weakest 
spot.  bear in mind that fuel does expand a lot, and the fumes above it do 
too.

On Thu, 18 Sep 2008 19:57:00 +0100, Mathew Newton   
wrote:

> [Sorry if you get this, or similar, twice - I one earlier and I think
> it failed - that'll teach me to use Google Groups!]
>
> I got a call from my neighbour today advising me that my girlfriends
> car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler
> cap.
>
> I couldn't get my head around how this could be, not unless she'd
> filled it right to the brim (it had been filled only at the weekend)
> and perhaps today's sunshine had increased the pressure such that it
> was now overflowing (to the tune of a drip every few seconds). But
> then it would really take some doing to fill it that much... right?
>
> So, when I got home I removed the filler cap and indeed found the
> petrol level to be right at the top... I wondered if the camber of the
> road had anything to do with it so replaced the cap and drove to a
> flat spot. When I got there I checked again and the level had dropped
> (completely out of sight in fact) and so I returned to the original
> parking position... and the petrol was still nowhere to be seen.
>
> I wondered if perhaps something had blocked the filler pipe and
> managed to keep the level high? And perhaps this blockage was now in
> the tank? But then surely this would have posed difficulties when she
> filled it... and the receipt shows a full tank (~30L) was I'm not so
> sure about the theory anymore...
>
> I'm now thinking more along the lines of a trapped air bubble? (I
> notice the filler pipe travels vertically down from the opening for
> around 8" and then horizontally for perhaps 20" to the tank. There
> appears to be two pipes to the filler - I don't know where the other
> goes (/comes from).
>
> Any ideas? I'm losing hair scratching my head on this one so your
> thoughts would be much appreciated!
>
> Incidentally, for what it's worth, the filler cap is a lockable
> aftermarket affair - when we bought the car a few years ago the cap
> was found to be one of those temporary push-in affairs. Also, we
> occasionally smell petrol inside the car (in the boot mainly, near the
> filler) and this is usually shortly after filling the tank. I've
> always put this down to sloshing fuel in the tank/filler and the
> likely less-than-perfect fitting of the aftermarket cap (whose gasket
> I see is starting to perish) which might be letting the occasional
> splash out to the surrounding area.
>
> Mathew


A 15 degC rise gives you 1.5% extra. If you top it up & leave it in the  
sun it can leak out the top. But the smell's probably a crap filler cap..

Mathew Newton expressed precisely :
> [Sorry if you get this, or similar, twice - I one earlier and I think
> it failed - that'll teach me to use Google Groups!]
>
> I got a call from my neighbour today advising me that my girlfriends
> car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler
> cap.
>
> I couldn't get my head around how this could be, not unless she'd
> filled it right to the brim (it had been filled only at the weekend)
> and perhaps today's sunshine had increased the pressure such that it
> was now overflowing (to the tune of a drip every few seconds). But
> then it would really take some doing to fill it that much... right?
>
> So, when I got home I removed the filler cap and indeed found the
> petrol level to be right at the top... I wondered if the camber of the
> road had anything to do with it so replaced the cap and drove to a
> flat spot. When I got there I checked again and the level had dropped
> (completely out of sight in fact) and so I returned to the original
> parking position... and the petrol was still nowhere to be seen.
>
> I wondered if perhaps something had blocked the filler pipe and
> managed to keep the level high? And perhaps this blockage was now in
> the tank? But then surely this would have posed difficulties when she
> filled it... and the receipt shows a full tank (~30L) was I'm not so
> sure about the theory anymore...
>
> I'm now thinking more along the lines of a trapped air bubble? (I
> notice the filler pipe travels vertically down from the opening for
> around 8" and then horizontally for perhaps 20" to the tank. There
> appears to be two pipes to the filler - I don't know where the other
> goes (/comes from).
>
> Any ideas? I'm losing hair scratching my head on this one so your
> thoughts would be much appreciated!
>
> Incidentally, for what it's worth, the filler cap is a lockable
> aftermarket affair - when we bought the car a few years ago the cap
> was found to be one of those temporary push-in affairs. Also, we
> occasionally smell petrol inside the car (in the boot mainly, near the
> filler) and this is usually shortly after filling the tank. I've
> always put this down to sloshing fuel in the tank/filler and the
> likely less-than-perfect fitting of the aftermarket cap (whose gasket
> I see is starting to perish) which might be letting the occasional
> splash out to the surrounding area.

If a bubble of air were trapped in the tank opposite the filler, 
combined with the fuel warming up after coming out of the ground - that 
would account for it overflowing. A quick drive round the block and the 
bubble moves to the filler neck.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Thu, 18 Sep 2008 11:57:00 -0700 (PDT), Mathew Newton 
wrote:


>So, when I got home I removed the filler cap and indeed found the
>petrol level to be right at the top... I wondered if the camber of the
>road had anything to do with it so replaced the cap and drove to a
>flat spot. When I got there I checked again and the level had dropped
>(completely out of sight in fact) and so I returned to the original
>parking position... and the petrol was still nowhere to be seen.

Dunno why it was too full in the first place but surely the level went down and
stayed down because you used the fuel to drive?

Geo

On 19 Sep, 15:21, Geo  wrote:
> On Thu, 18 Sep 2008 11:57:00 -0700 (PDT), Mathew Newton 
> wrote:
>
> >So, when I got home I removed the filler cap and indeed found the
> >petrol level to be right at the top... I wondered if the camber of the
> >road had anything to do with it so replaced the cap and drove to a
> >flat spot. When I got there I checked again and the level had dropped
> >(completely out of sight in fact) and so I returned to the original
> >parking position... and the petrol was still nowhere to be seen.
>
> Dunno why it was too full in the first place but surely the level went down and
> stayed down because you used the fuel to drive?
>
> Geo

I only went 200 yards... :-)

I think the air bubble in the horizontal section of the filler pipe is
sounding like the most feasible explanation. It may well never happen
again, and besides I'll get a new filler cap which may provide a
better seal to at least likely solve the occasional fumes-in-cabin
issue.

Thanks everyone for the input,

Mathew

"Mathew Newton"  wrote in message 
news:da7bcc8a-d1dc-4ffb-b278-0dfff9672de4@v16g2000prc.googlegroups.com...
> [Sorry if you get this, or similar, twice - I one earlier and I think
> it failed - that'll teach me to use Google Groups!]
>
> I got a call from my neighbour today advising me that my girlfriends
> car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler
> cap.
>
> I couldn't get my head around how this could be, not unless she'd
> filled it right to the brim (it had been filled only at the weekend)
> and perhaps today's sunshine had increased the pressure such that it
> was now overflowing (to the tune of a drip every few seconds). But
> then it would really take some doing to fill it that much... right?
>
> So, when I got home I removed the filler cap and indeed found the
> petrol level to be right at the top... I wondered if the camber of the
> road had anything to do with it so replaced the cap and drove to a
> flat spot. When I got there I checked again and the level had dropped
> (completely out of sight in fact) and so I returned to the original
> parking position... and the petrol was still nowhere to be seen.
>
> I wondered if perhaps something had blocked the filler pipe and
> managed to keep the level high? And perhaps this blockage was now in
> the tank? But then surely this would have posed difficulties when she
> filled it... and the receipt shows a full tank (~30L) was I'm not so
> sure about the theory anymore...
>
> I'm now thinking more along the lines of a trapped air bubble? (I
> notice the filler pipe travels vertically down from the opening for
> around 8" and then horizontally for perhaps 20" to the tank. There
> appears to be two pipes to the filler - I don't know where the other
> goes (/comes from).
>
> Any ideas? I'm losing hair scratching my head on this one so your
> thoughts would be much appreciated!
>
> Incidentally, for what it's worth, the filler cap is a lockable
> aftermarket affair - when we bought the car a few years ago the cap
> was found to be one of those temporary push-in affairs. Also, we
> occasionally smell petrol inside the car (in the boot mainly, near the
> filler) and this is usually shortly after filling the tank. I've
> always put this down to sloshing fuel in the tank/filler and the
> likely less-than-perfect fitting of the aftermarket cap (whose gasket
> I see is starting to perish) which might be letting the occasional
> splash out to the surrounding area.
>
> Mathew



I doubt this is related to the problem but I remember replacing my parents' 
Humber Sceptre locking filler cap with an aftemarket one.
Apparently the original had a breather to let air into the tank as the 
petrol level dropped, the replacement didn't.  Consequently as the petrol 
got used up, there was no way for air to replace it as the new cap was an 
airtight seal.  The tank slowly imploded until it would hold no more than 
about 2 gallons.

If I hadn't removed the flattened tank and replaced it I would never have 
believed this could happen.



Gareth.

Gareth Magennis wrote:

[...]
> 
> I doubt this is related to the problem but I remember replacing my
> parents' Humber Sceptre locking filler cap with an aftemarket one.
> Apparently the original had a breather to let air into the tank as the
> petrol level dropped, the replacement didn't.  Consequently as the petrol
> got used up, there was no way for air to replace it as the new cap was an
> airtight seal.  The tank slowly imploded until it would hold no more than
> about 2 gallons.
> 
> If I hadn't removed the flattened tank and replaced it I would never have
> believed this could happen.
 
Oh, it sure can!

It was a "feature" built in to early Ford Granadas...

Chris

-- 
Remove prejudice to reply.