Discussion
Whilst replacing the very dim headlights with some nice new shiny ones i found a black plastic cylinder hiding in the drivers side headlight void.......it's about 110mm round and 150mm tall with connections labeled Purge/Tank/Air and an electrical connection too!
What is it
is it important
how do i test it
should i just put it back?
Headlamp replacement on hold for now!
What is it
is it important
how do i test it
should i just put it back?
Headlamp replacement on hold for now!
It's your carbon canister. You don't really need it as it's there purely to pass SVA but is not needed to pass an MOT. The way it works is as follows:
The fuel tank has a rubber vent pipe that goes out of the tank, through a roll-over non return valve in the boot and then routes down the car and into the CC. The carbon filter inside allows the tank to vent but catches any fuel vapour from escaping. To prevent the filter getting blocked, the CC has another pipe that runs up the wing and pops out next to the cover above the clutch master cylinder (its the smaller pipe closer to the front of the car than the other one, which is the brake vac advance I think). Anyway when certain conditions are met within the ECU, something like 4k revs, only once after each engine start, a valve in the canister opens. This purge valve clears out the canister by using the vacuum from the plenum to suck all of the excess fuel vapour from the CC into the inlet manifold.
From what I've seen, most CC's have been blocked off in the past as they can cause fuel tank venting problems. This is done by blocking the plenum hose up with a bolt (or as I have done, remove the hose altogether and block up the hole left in the trumpet base). Then disconnect and remove the CC, but remember to pull the fuel tank vent pipe back to the rear of the car and allow it to vent somewhere where you don't mind depositing a bit of fuel vapour. Mine is vented directly below the fuel tank, through those 3 holes in the body just to the rear of the near side rear wheel arch which works fine for me. You could leave the fuel vent in the nose of the car if you want, but you will get a slight smell of fuel for a couple of seconds after startup as air is sucked in to the blower system, but this is hardly noticeable.
In short it does no harm, but IMHO you don't need it and if you might as well remove it, just remember to block the vacuum feed and move the fuel vent hose if you don't want to smell fuel on startup.
Hope that helps!
edit: bigdods' reply is much better than my essay, but I'm bored sitting in a hotel in Norfolk so I stand by it...!
The fuel tank has a rubber vent pipe that goes out of the tank, through a roll-over non return valve in the boot and then routes down the car and into the CC. The carbon filter inside allows the tank to vent but catches any fuel vapour from escaping. To prevent the filter getting blocked, the CC has another pipe that runs up the wing and pops out next to the cover above the clutch master cylinder (its the smaller pipe closer to the front of the car than the other one, which is the brake vac advance I think). Anyway when certain conditions are met within the ECU, something like 4k revs, only once after each engine start, a valve in the canister opens. This purge valve clears out the canister by using the vacuum from the plenum to suck all of the excess fuel vapour from the CC into the inlet manifold.
From what I've seen, most CC's have been blocked off in the past as they can cause fuel tank venting problems. This is done by blocking the plenum hose up with a bolt (or as I have done, remove the hose altogether and block up the hole left in the trumpet base). Then disconnect and remove the CC, but remember to pull the fuel tank vent pipe back to the rear of the car and allow it to vent somewhere where you don't mind depositing a bit of fuel vapour. Mine is vented directly below the fuel tank, through those 3 holes in the body just to the rear of the near side rear wheel arch which works fine for me. You could leave the fuel vent in the nose of the car if you want, but you will get a slight smell of fuel for a couple of seconds after startup as air is sucked in to the blower system, but this is hardly noticeable.
In short it does no harm, but IMHO you don't need it and if you might as well remove it, just remember to block the vacuum feed and move the fuel vent hose if you don't want to smell fuel on startup.
Hope that helps!
edit: bigdods' reply is much better than my essay, but I'm bored sitting in a hotel in Norfolk so I stand by it...!
Edited by thenick on Sunday 22 June 17:54
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