The hose that goes nowhere!

Post Mon Mar 30, 2015 2:34 pm

I found this hose tucked away in a corner! I followed it to the fuel tank. It is the fuel line that is the most toward the sill.

The car is an m50b25 318i 1989.

Is this the fuel tank vent and what should I do with it?

Thanks

JF

Post Mon Mar 30, 2015 3:25 pm

It is indeed the fuel tank vent. It can be tucked in the inner wing out of the way - probably where you found it? Filter it if you like with a little K&N alikey but doesn't really need it. I removed the entire vent line back to the flexi from the tank - put a little universal fuel filter on that with some activated carbon in it and clipped it up over the fuel tank out the way.

Post Mon Mar 30, 2015 3:44 pm

As it's the vent pipe, it certainly shouldn't be blocked off!

Post Mon Mar 30, 2015 3:47 pm

I though I would have to butt it in an intake port. It could explain the big WOOOSH when I open the petrol cap. Where does the vent pipe go on a factory e30?

Post Mon Mar 30, 2015 3:48 pm

Does the tank "hiss" when it's empty and you open the fuel cap ?

Post Mon Mar 30, 2015 3:50 pm

jimbom30cab wrote:Does the tank "hiss" when it's empty and you open the fuel cap ?

Hiss or whooosh, its open to interpretation I guess

Post Mon Mar 30, 2015 4:34 pm

I will leave it open and tucked in the turret for now.

Found in the wiki:

''To meet increasingly stringent emissions regulations, later engines were fitted with a Carbon Canister. This small brown container sits in the engine bay and is bolted to the inner wing. It captures fumes from the fuel tank venting system, filtering them through a self-contained carbon filter and releases them into the throttle body. The carbon canister was controlled by a small electric valve. If you find an unused plug on the loom underneath the throttle body, it is for this valve.

Utterly redundant, the Carbon Canister system causes more problems that it solves in older cars, and is recommended to be removed if found, or at least disabled.

Removal is simple. When disconnecting, the end of the rubber hose to the canister from the back of the car MUST be left open, and should be tucked inside the reinforcement for the suspension turret. The hose from the valve that goes towards the inlet manifold MUST be blocked off and airtight, either by a plug in the end of the hose, or a cap on the metal stub pipe into the manifold.

For cars not fitted with the Carbon Canister, it is this blanking plug on the intake that is a major cause of air leaks. ''

Post Mon Mar 30, 2015 5:14 pm

Motorhole wrote:It is indeed the fuel tank vent. It can be tucked in the inner wing out of the way - probably where you found it? Filter it if you like with a little K&N alikey but doesn't really need it. I removed the entire vent line back to the flexi from the tank - put a little universal fuel filter on that with some activated carbon in it and clipped it up over the fuel tank out the way.

Your better off running it downwards into a flow of air, this takes away the explosive gas that you now have sitting around your fuel tank
It also stops fuel draining out if you end up on the roof

Post Mon Mar 30, 2015 5:24 pm

DanThe wrote: Your better off running it downwards into a flow of air, this takes away the explosive gas that you now have sitting around your fuel tank
It also stops fuel draining out if you end up on the roof

Fair points both, particularly the latter! I will revise this as I slowly work through my current phase of minor bodge reversals

Post Mon Mar 30, 2015 5:39 pm

JF008 wrote:Where does the vent pipe go on a factory e30?

You've answered your own question...

JF008 wrote:I will leave it open and tucked in the turret for now.

If you're removing the carbon canister you will need to block the pipe off at the inlet manifold end (or you will have a big air leak), but the vent pipe from the tank must be left open so it can vent to atmosphere.

Post Mon Mar 30, 2015 6:13 pm

Thanks for the replies

JF

Post Mon Mar 30, 2015 7:01 pm

For the hole on the throttle body I usually cut the brass off flush, tap it out and thread lock a set screw in. No air leaks there again, ever

Post Wed Apr 08, 2015 10:46 pm

Why not let the tank vent into the intake system? Like using a y fitting and connecting it to the intake boot. Any ill effects?

JF

Post Thu Apr 09, 2015 12:01 am

With the throttle open and engine sucking in air, that will try to create a vacuum in the fuel tank

It's a vent pipe, leave it be.

Post Thu Apr 09, 2015 12:16 am

JF008 wrote:Why not let the tank vent into the intake system? Like using a y fitting and connecting it to the intake boot. Any ill effects?

JF

That's what it does do when all the emissions bits are fitted, BUT only via an ECU controlled solenoid valve, otherwise it would be an unmetered air leak with the throttle open, and would collapse the fuel tank with the throttle shut.

Post Fri Apr 10, 2015 4:41 pm

Ok thanks guys I will have to get over it

Post Fri Apr 10, 2015 8:10 pm

Some E30's vent near the tank and others in the bay.