Hi all,

Okay, it's a 96 1.3 escort.  Had to replace my petrol cap a while back
as it suddenly wouldn't lock.  Halfrauds wee thin locking one was
bought which did the job but wasn't anything like the depth of the old
one yet was supposedly the right one for me.  Thinking recently, this
replacement doesn't seem to hold anything like the pressure (take it
off at the pumps, nothing like the hissss of old, almost negligible
really) so I figure it's obviously crap and costing me fuel, but how
much?  If I effectively have a vent at the end of the line instead of a
sealed system and therefore maybe only a few hundred millibars pressure
then I can see it potentially squirting out, what, 1/2 litre every 50
miles or so? (really just a picture in head type of calculation).  Plus
what would the engine be thinking about this lack of pressure?  Or
would nothing at that end notice the difference?  Have a replacement
proper cap (or so they say) available for £21 odds.  Worth it in lost
fuel?  I have no real idea on this one.

Chandy

"Chandy"  wrote in message
news:1124400964.142371.121860@g47g2000cwa.googlegroups.com...


> Okay, it's a 96 1.3 escort.  Had to replace my petrol cap a while back
> as it suddenly wouldn't lock.  Halfrauds wee thin locking one was
> bought which did the job but wasn't anything like the depth of the old
> one yet was supposedly the right one for me.  Thinking recently, this
> replacement doesn't seem to hold anything like the pressure (take it
> off at the pumps, nothing like the hissss of old, almost negligible
> really) so I figure it's obviously crap and costing me fuel, but how
> much?  If I effectively have a vent at the end of the line instead of a
> sealed system and therefore maybe only a few hundred millibars pressure
> then I can see it potentially squirting out, what, 1/2 litre every 50
> miles or so? (really just a picture in head type of calculation).  Plus
> what would the engine be thinking about this lack of pressure?


Couple of things.  Firstly it's not pressure, it's vacuum.  Secondly it's
not supposed to suck air in when you remove the cap; it means a vent is
blocked, probably, and in extreme cases you can get poor running or even
cutting out because it's effectively sucking back against the pump.  Usually
it won't do any harm though.

I would replace the cap for the correct one in any case.  Perhaps you can
transfer your original lock barrel over if it still works, or get one
ordered to match your locks.

"Chandy"  wrote in message 
news:1124400964.142371.121860@g47g2000cwa.googlegroups.com...
Hi all,

Okay, it's a 96 1.3 escort.  Had to replace my petrol cap a while back
as it suddenly wouldn't lock.  Halfrauds wee thin locking one was
bought which did the job but wasn't anything like the depth of the old
one yet was supposedly the right one for me.  Thinking recently, this
replacement doesn't seem to hold anything like the pressure (take it
off at the pumps, nothing like the hissss of old, almost negligible
really) so I figure it's obviously crap and costing me fuel, but how
much?  If I effectively have a vent at the end of the line instead of a
sealed system and therefore maybe only a few hundred millibars pressure
then I can see it potentially squirting out, what, 1/2 litre every 50
miles or so? (really just a picture in head type of calculation).  Plus
what would the engine be thinking about this lack of pressure?  Or
would nothing at that end notice the difference?  Have a replacement
proper cap (or so they say) available for 21 odds.  Worth it in lost
fuel?  I have no real idea on this one.

Chandy


I doubt whether losses  could be calculated.  But an insecure petrol cap is 
an mot failure, so I would say, get the ford cap and return the crap one to 
halfords as it is 'unsuitable for the purpose supplied'

mrcheerful

> I would replace the cap for the correct one in any case.  Perhaps you can
> transfer your original lock barrel over if it still works, or get one
> ordered to match your locks.


I'd suggest you do as the man above says, and get it from your local
scrapyard.  Certainly around 1996, the Ford petrol caps with central locks
were easy to swap locks from cap to cap....

Artie