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Fuel Tank Pressure '72 Spit 1300

Bob Percer

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I've been experiencing a problem where on a long run, the car looses power and cuts out.  When I open the fuel filler cap there is a whoosh of either suction or pressure (not sure which as it's always somewhere scary) and I can then start up and drive normally.  Obviously this build up is preventing the fuel pump drawing fuel from the tank.  Is there a vacuum being created and would the breather be to blame?  My breather is on top of the tank next to the fuel pick up pipe and has a short length of rubber pipe on it with a plastic door lock button in it fixed in with a hose clip.  Not a factory standard...

Any help/ideas gratefully recieved.



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Sounds like a blocked breather. And yes, vacuum in the tank. Brain not fully functioning, but that breather you mention is supposed to be capped off, otherwise you get a strong smell of petrol in the car (it was for US emissions stuff I think). Think it should breathe through the cap??

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Open breathers went out tubed thro a grommet in the floor aside the tank

these disappeard with intro of roll over fuel spillage rules in the late 70s


some have sealed caps and some need the cap seal with a breather hole

If a non breather & sealed cap has been fitted to a non spill tank you get your problem


so fit a tube or change the cap seal



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Two ways to safely vent to the tank.


1/ Run a hose from that tank vent tube as high as possible above the tank and then down and out through a hole in the boot floor.   This will prevent any fuel splashed into the hose from escaping, and in the unlikely but dangerous situation of inverting the car, will put the opening above the tank, so fuel will not run out.  As long as the end is outside the car, little or no fuel smell.


2/ Buy a "Fuel Non-Return Valve", insert it in the hose and exit the hose as above, without the long route.   The valve will allow air to get in and prevent the vacuum, but not allow fuel to get out.

Plenty to choose from: https://www.google.co.uk/search?q=Fuel+non-return+valve&biw=1816&bih=1019&source=lnms&tbm=isch&sa=X&ei=b09DVdzPOpPKaJCqgZAG&ved=0CAcQ_AUoAg



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  • 3 weeks later...

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