Fuel Tank Vent

[mikesr]

There have been a few threads re fuel tank venting including mine
Despite blowing and sucking I was still getting air whooshing in when the filler cap was removed and sometimes a weird squeaky whistling noise when air was being sucked through the valve.

So I replaced the black plastic ford rollover valve with nice alloy Mocal one.

There is now no whooshing of air into the tank when I open the filler cap.

So it looks like it was a partially blocked (or not very good in the first place) rollover valve that was causing the hassle.

Mike

[ajp4.2]

mikesr said:

There have been a few threads re fuel tank venting including mine
Despite blowing and sucking I was still getting air whooshing in when the filler cap was removed and sometimes a weird squeaky whistling noise when air was being sucked through the valve.

So I replaced the black plastic ford rollover valve with nice alloy Mocal one.

There is now no whooshing of air into the tank when I open the filler cap.

So it looks like it was a partially blocked (or not very good in the first place) rollover valve that was causing the hassle.

Mike

Hi Mike
Where is this valve located?

[mikesr]

Have a look at this thread

There are some pictures there. The valve is in the boot above the fuel tank on the near side. Its bolted to the body shell that backs onto the rear seats.

You will need to un-velcro 2 or 3 of the black control boxes that sit around the fuel tank filler pipe to see it.

[foxy4200]

Hi Mike

If you look back through some old threads, I had my fuel system in pieces. I found that my cut off valve was a bit erratic aswell, almost like it was partially blocked. It works ok most of the time, but i do still have trouble with it. Think I'll replace it with the same one youve used, where can i buy one from?

Thanks

Rich

[mikesr]

I got mine from www.merlinmotorsport.co.uk

The Mocal TRL7 valve

I used a s/steel rubber lined P clip to mount it on the bolt that the exisiting one was fastened to.

Can't remember the size of the P clip - about 20mm I think but it was a tad too big.

Demon tweeks stock them as well. I think they list it as a medium flow inline filter.

Mike

[SimonSparrow]

Bit of an old one this, but I've had the same symptoms on my car (fuel tank 'wooshing' when cap removed etc.

I've maybe gone a bit too simple and have just blocked off the TVR ventilation system, and just run a breather hose outside the body (I have some vents in the boot floor where the hose fits through).

Is this a bad idea?

I was thinking of removing the TVR vent system when I (finally) install the oil catch tank I've had for two years, again, are there any disadvantages with this?

My assumption is that the vent system for the fuel tank and oil breather is to reduce environmental impact. Whilst I don't wish to increase environmental damage, my thinking is that a better running Cerbera may be of more benefit to the planet, than one with a half hearted breather implementation.

[mikesr]

The valve is a rolover valve that stops fuel siphoning out if the car is inverted. So maybe a bad idea if you end up on the roof. Very likely contravenes some rule or other and invalidates the insurance.

The other venting to the carbon can is from the intake manifolds, not from the cam chest like the large bore breather pipe. So removing it completely is probably not a good idea.

I asked a while back if anyone new what positive effect the inlet manifold venting had? Anyone know the answer?

[SimonSparrow]

mikesr said:

The valve is a rolover valve that stops fuel siphoning out if the car is inverted. So maybe a bad idea if you end up on the roof. Very likely contravenes some rule or other and invalidates the insurance.

The other venting to the carbon can is from the intake manifolds, not from the cam chest like the large bore breather pipe. So removing it completely is probably not a good idea.

I asked a while back if anyone new what positive effect the inlet manifold venting had? Anyone know the answer?

I've run it for a few days with the TVR vent hoses blocked off at the fuel tank and the tank venting to outside the car. Can't say I've noticed a big difference either way, apart from the fact that the tank doesn't 'woosh' when I go to refill it.

[mikesr]

Have you blocked off both hoses that go to the carbon can in the nearside rear wheel arch?

The one that vents from the inlet manifolds doesn't go near the fuel tank.

[mikesr]

wikipedia provides the answer to the carbon can venting

"Capturing vented vapors

Within the vehicle, vapors from the fuel tank are channelled through canisters containing activated carbon instead of being vented to the atmosphere. These are known as carbon canisters. The vapors are adsorbed within the canister, which feeds into the inlet manifold of the engine. When the vehicle is running, the vapors desorb from the carbon, are drawn into the engine and burned."

[SimonSparrow]

Thanks for the info Mike, I've put it back to standard for now as it didn't seem to make a difference anyway.

But no, I hadn't blocked off those hoses, if I do it again, I'll remember those.

[southendpier]

My tank "Wooshes" never seems to be a problem, even when running down to near empty.

Is it a problem?

[WIL35]

On mine the other night, after a 90 mile run I stopped the car to grab a coffee then restarted. It was idling at about 1400 revs and there was an unusual noise from the back of the car. I got out, opened the fuel tank, had the usual whoosh and the idle speed went back down to its usual level!

Is this normal?

[thegreengoblet]

southendpier said:

My tank "Wooshes" never seems to be a problem, even when running down to near empty.

Is it a problem?

I always thought that it had to do this?? Mine does it.