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Fuel Breather Pipe - Block it or?


Scott

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I've asked this question before but I didn't really get a solid answer. I've removed the charcoal canister from my car and so I have been left with the fuel tank breather pipe in the engine bay. Should I block this off or leave it open to the atmosphere? I'm just worried of the fumes igniting or something dangerous like that. At the moment I have a wee silicone cap over it.

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Extend it, and route it through the hole in the inner wing (where the cc was), and into the passenger wheel arch bud

 

So there's absolutely NO chance of fuel coming out of it, and there's no way it'll be expelling precious fuel out there? I understand that the charcoal canister was kind of air tight?

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The fuel tank needs to vent, otherwise it can implode. It's only fuel vapour that comes out of the line.

The charcoal cannister basically filters the fumes, and vents them back into the inlet manifold.

 

Fuel will definitely not come out of the line mate.

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Charcoal Canister removal mod

 

 

I have looked into the charcoal canister removal mod, and it appears that no one has thought the job through properly!

 

The Supra fuel tank and pump are designed to operate at a positive pressure of 2psi.

 

The fuel filler cap, is a 2psi relief valve, maintaining pressure on charcoal filter up to 2psi and gently venting excess.

 

Without the pressure gurgling out through the charcoal filter, the cap has a little more relieving to do.

 

3 pipes on charcoal canister, listed below with direction of flow.

 

1 goes to induction vacuum.

1 comes from fuel tank.

1 goes to drain.

 

Remove vacuum pipe from inlet manifold and cap it off.

Pipe to fuel tank can be capped, or removed completely and blanked off on tank.

Drainpipe can be left open, or removed completely.

 

Simples !

 

A tidier job and minor weight reduction is made by removing pipes and blanking at source.

 

(An even simpler explanation is; remove it and blank off the pipes.)

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Please show me where it says the fuel tank should see positive pressure!!! If that were the case, and you had a full tank, removing the filler cap would vent fuel over someone. I have NEVER seen a fuel tank on a production car that SHOULD or DOES run pressurised, but most have some vacuum, and you can hear air rush INTO the tank when you remove the filler cap.

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Rattling petrol about in a sealed tank creates vapour which creates pressure faster than a fuel pump can reduce it, not vacuum.

 

It is this positive pressure that the charcoal filter system is all about, which without pressure to push these vapours through it, would be merely an ornament and the pressure relief valve is a one way, out only valve.

 

Suck and blow makes a similar noise, but suck would stick the cap to the tank, which it doesn't.

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If it was a vacuum, Mr T. would not have wasted profit fitting a charcoal filtration system to filter fuel vapours from the positive pressure.

 

They could still fit a charcoal filtration system vacuum controlled via the intake to filter fuel vapour though. With a 2psi vacuum relief on the cap and a constant vacuum pull from the intake/fuel drop there would be no chance of any leaks around the system. Vacuum prevents leaks, positive pressure causes them.

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The charcoal filter relieves petrol vapours from positive pressure. That's what it is for!

 

The fuel cap is a 2psi positive pressure relief valve.

 

Please research this instead of blindly following an old wives tale.

 

Please point out any links to back up your claims and I will gladly read them.

 

- - - Updated - - -

 

If a fuel tank is not vented it would gradually reduce the fuel available to the injectors because the vacuum created by the fuel displacement would make it harder for the pump to produce positive pressure to the fuel system.

 

It'll be vented regardless due to the relief on the fuel cap :)

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