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Old 11 Apr 2006
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Is my fuel tank breather blocked?

My Hilux has a small black valve on the breather pipe with an arrow pointing out (i.e. away from the tank) which to me indicates that it is a one-way valve to allow air to escape from the tank (i.e. due to thermal expansion of the air in the tank). The trouble is, it does not allow air to come into the tank to replace fuel as it is drawn to the engine. This is evidenced by a rush of inward moving air when removing the fuel filler cap (the cap has no breather / hole). Once, when the tank was really empty, the vacuum was so strong it starved the engine of fuel.

I've blown the the valve myself, and can confirm it only allows air to travel in one direction.

Now, Toyota's being as well designed as they are, I'm wondering what's gone wrong here. Is it that someone has fitted the valve back to front in the breather line? Or is there a problem with the send / return mechanism in the fuel pump?

At present I'm running it without the valve in the breather line, without any problems. No air movement when removing the filler cap.

Any help would be much appreciated,


4.5 years around Eurasia in a Toyota Hilux|http://eurasiaoverland.wordpress.com/
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Old 12 Apr 2006
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Smile Strange...

Hi Dan, not so sure on Toyotas - but most vehicle manufactors used to use breathers in the filler caps (on slightly older models) so maybe at some point the cap has been replaced with a non standard ???
OR As you say maybe the valve has been refitted the wrong way around ??? - try fitting it in other way around and see how it goes for a while.

'09 Suzuki DR650
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Old 13 Apr 2006
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The new laws are that a gas tank can not vent to the atmosphere.
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Old 19 Apr 2006
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If your fuel cap is anything like the 80 series landcruisers then you will have a vent valve in the cap. This can be dismantled, but do it carefully because the plastic can get quite brittle and I seem to recall a spring bouncing out.

Also on the 80 the tank breather seems to have a small in line filter (similar to the small plastic fuel filters you can get) - I have removed this on mine and extended the breather pipe up and out of the way from dirt/water ingress.

Julian Voelcker
Overland Cruisers - Specialising in Land Cruiser preparation and servicing.
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Old 21 Apr 2006
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Originally Posted by CZrider
The new laws are that a gas tank can not vent to the atmosphere.
Indeed. The fuel tank should 'vent' to a charcoal filled canister - the motor, when, running draws air from there so burning any petrol fumes before they get to us.

Possibly your charcoal canister has been flooded with liquid petrol (rather than vapour) and is blocked. Find it and test if you can blow through it ... beware of sucking petrol! Should be somewhere in the engine bay if they have done things right.. but it could be elsewhere. Or someone has blocked off the polution control lines .. and has done this one too?
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
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Old 23 Apr 2006
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There's no such charcoal filter on my car - for the record it's a diesel - I don't know whether this makes any difference? My guess is that my car (1993) pre-dates any such charcoal chenanegans.

Julian - I think your 80 Landcruiser has the same setup as my 105 Hilux, but there is no breather as far as I can see in the cap. I do have a spare, which I may try but since removing that filter / valve on the tank breather (not filler) has resolve the issue, I think I'll just copy your idea, and extend the pipe up behind the cab.

As long as the problem is not with my fuel pupm, I'm happy.

Thanks for all your replies,

4.5 years around Eurasia in a Toyota Hilux|http://eurasiaoverland.wordpress.com/
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