Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: terry paget on 04 September 2018, 08:43:49
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To allow the engine to run continuously air must get into the tank to replace fuel consumed. As the filler cap seals, the only route remaining is the hose to the purge chamber, which in turn is linked via the purge valve to the inlet breather. So is the valve open all the while the engine is running?
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In the "old days" wasn't there a breather pipe from the top of the tank?
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In the "old days" wasn't there a breather pipe from the top of the tank?
On my motorbikes there was a small hole in the filler cap.
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To allow the engine to run continuously air must get into the tank to replace fuel consumed. As the filler cap seals, the only route remaining is the hose to the purge chamber, which in turn is linked via the purge valve to the inlet breather. So is the valve open all the while the engine is running?
Which obviously won't work as the vapour system is a) intermittent, and b) obviously a vacuum into the intake manifold ::)
Cap is primarily to prevent spillage, purge valve/carbon canister draw off vapour build up and filler balance pipe and cap should regulate tank pressure :y
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The fuel tank can breathe only through the charcoal canister under the offside front wing.
When the vehicle is parked, vapours given off by the fuel get absorbed by the charcoal in the charcoal canister instead of being released into the atmosphere.
When the vehicle is being driven, air can normally enter the charcoal canister and hence into the tank to replace displaced fuel via a non-return valve that only allows air to enter. In addition, the engine can draw clean air in through the charcoal via the purge valve, and this purges the charcoal of fuel vapour ready for the next time the car is parked.
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That's me told then ;D
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Haynes says Trace the filler neck vent hose back to its connection on the right hand side of the tank . :y
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One of the (many!) faults on a Lotus Carlton is that the charcoal purge canister can get blocked. Then as the fuel is used up, the fuel tank is sucked in. Eventually the fuel tank collapses and any remaining fuel pi55es all over the floor. :o
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Don't these these carbon canister systems typically (maybe all) have built-in air filter as well as a non-return valve. Air is drawn into the canister as described by Kevin Wood above. I suppose it's entirely possible that the filter and/or the valve gets blocked over time.
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Thinking about all this, what failure of this system would cause a strong fume smell to enter the cabin?
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Don't these these carbon canister systems typically (maybe all) have built-in air filter as well as a non-return valve. Air is drawn into the canister as described by Kevin Wood above. I suppose it's entirely possible that the filter and/or the valve gets blocked over time.
I've not taken one apart but I guess so. There's always the possibility of blockage so it's a good job some muppet didn't put it behind the front wheel where there's loads of mud. Oh, wait! ::)
Thinking about all this, what failure of this system would cause a strong fume smell to enter the cabin?
There shouldn't be anywhere it can enter the cabin but I guess the main possibilities are a leak under the tank cover in the boot or perhaps fumes able to exit the charcoal canister in the front wing. I guess that could find its' way into the cabin.
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Coming through the dash vents, so obviously engine bay related... Fumes smell like a mix of petrol and hot oil (but notably different to old oil/breather fumes and no oil, or any other, leaks on the engine beyond an as yet un located exhaust leak... Suspect cat is starting to blow.)
Upon investigation, the vapour lines are plastic with rubber elbows and all intact...
However, the rubber hose from the end of the fuel feed pipe to the fuel rail is badly perished although not leaking fluid... I wonder if this is the source of the fumes :-\