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Post by Zed. on Mar 9, 2019 13:20:06 GMT
was unsure where to ask about this the previous owner of my car did all the usual 'must-have' mods as seen on fb & forums - hence the charcoal canister delete (& mk2 dash swap (returned back to mk1) / ac removal & (ANNOYINGLY) also removed the PAS ) and I wonder what has been done - I'm slowly undoing these and other 'upgrades' and the car now works anyway, as I say, the fuel tank pressurises after a drive, when opening the cap ist releasing a puff of fuel vapour and I wonder if anyones suffered with this or is it a Mazda design quirk? my Eunos has always had a pressurised fuel tank, I'm guessing theres a blocked or sticky vent-valve somewhere, possibly connected to the vent pipework that used to feed the canister thats been deleted? I appreciate that the cap has a vent-valve or pressure-relief valve and thats something on my list to inspect (one day hopefully, I've been thinking about this for a year... ) Rich.
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Post by wannabe on Mar 9, 2019 14:26:59 GMT
Mine does this and the missus' (90s Jap car) also does this - I thought this was just a thing, perhaps from where the fuel heats up as the car body heats up a bit from brakes/air friction/etc.?
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Post by dickie on Mar 9, 2019 14:31:50 GMT
Hi Zed, I would say its normal to get a pressurisation of the Mx 5 Tank, It has happened on the last three cars of mine. It happens with or without the charcoal canister. Exhaust heat and the heat from the fuel pump will all add up to vapour expansion. I think there is a relief valve above the tank under the deck cover.
Cheers Dickie
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Post by Zed. on Mar 9, 2019 17:10:08 GMT
Exhaust heat and the heat from the fuel pump will all add up to vapour expansion. I think there is a relief valve above the tank under the deck cover. *somehow* I managed to ignore the exhaust heat from below the tank guessed it was the engine warming the fuel easy to miss the obvious (MY excuse!) will have a looksee at the top of the tank Rich.
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Post by Zed. on Apr 23, 2019 10:41:57 GMT
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Post by wannabe on Apr 23, 2019 11:03:08 GMT
What is the check valve for?
I'd want to replace it rather than just delete it, just in case... lol
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Post by Zed. on Apr 23, 2019 11:29:35 GMT
What is the check valve for? I'd want to replace it rather than just delete it, just in case... lol ^^Same theres a 'roll-over' valve on the tank then this 'check-valve' - what's it 'check'? I'm guessing it's containing something like a ball that 'floats' between the pipes to block if on an angle? think I've a sapre one from a breaker so will have a looksee & maybe swap it over Rich.
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Post by JamesMk3 on Apr 23, 2019 12:10:53 GMT
...then this 'check-valve' - what's it 'check'?... Check-valve is just another term for a one-way/non-return valve. More common use in American English.
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Post by martiny on Apr 23, 2019 12:39:07 GMT
...then this 'check-valve' - what's it 'check'?... Check-valve is just another term for a one-way/non-return valve. More common use in American English. "Check" in its meaning of "stop" rather than "make sure". Anyway, I really just dropped in to say both my Mk.1's have exhibited the "pshhht" of slight pressure in the fuel tank when opened, unless the car was still cold. The main reason the pressure builds up (I assume) is because the fuel is heated as it's constantly pumped to the (hot) fuel rail and the excess returned to the tank. I wonder if later Mk2.5s with returnless fuel systems don't do this.
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Post by atlex on Apr 23, 2019 12:53:52 GMT
^Martiny - I experienced it on my mk2.5 also...
from what I know, there is a certain amount of 'normal' gas pressure that the tank will have if there is fuel in there, the check valve is more than a one-way valve, it'll vent if there is *too much* but it won't vent if the pressure is within normal limits i.e. a few psi. that's the psssht we get when we open the tank up to fill it. if you don't get a psssht + you have a gassy smell when cold then the check valve may have failed open.
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Post by Zed. on Apr 28, 2019 10:11:52 GMT
with the power of spares & hoarding, I've investigated one of these 'check-valve' thinggies (& the 'roll-over' valve) so, bolted to the top of the tank theres a 'roll-over' valve as a safety item in case of the ' driver' having an issue & running out of tallent or being the first to arrive at the scene of the accident - obviusly this refers to tipping the car then attached with a short length of pipe is said ' check-valve'... its an aluminium-ish construction that looks to be non-serviceable so if it's Jeffed then bin & replace, testing was done scientifically (blow through both ends to see what happens ) and this shows it's normally 'closed' and opens with pressure or vacuum. maybe later I'll strip the back of my car & 'test' the one on it Rich.
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