Carbon canister removed issue

You got it backwards. Purple line is vent up to intake manifold. Green line is to tank. This way, tank can release air to the canister if more than 1psi is achieved (parking in sun on hot day?) And of course suck air if car is running.

Also, I decided not to use the fuel filter, already busy space in there.

Revised annotation.

Also: Greg, is the vacuum switch in the line not visible an existing vacuum switch?

some time ago I did what your drawing shows with no filter and have drove many years that way… peace of mind… however I never got rid of trunk smell and quit chasing the ghost… someday I may find it… if one lives long enough and still has the car… sort of laughing at all the time spent

The last thing you might want to do is replace the metal pipe connecting the fuel tank in the trunk to the hoses under the drivers rear wheel.

yes… is that the one with a ferule on the line

Npt a jaguar odea. It s GM. I have a GM unit in my bits totes. My lump uses the cannister that Jaguar instaled. Same as far as I can see.

I have read here that some just poke a hole in the rochester. always open. No harm???

At worst, a minor vacum leak one might nevrer sense.

This is probably where I stick my foot in my mouth and get environmentally conscience Jag Lovers mad at me. I’m not sure what JL members do about their older XK150’s but if you go through our archives and the amount of conversations about fuel smells, vacuum and pressure in gas tanks. I think we can all agree that Jaguar screwed the pooch on their solutions.
Hey do sea turtle shove plastic straws up their nose? I dunno? Does Russia launch mach 5 missiles into the Ukraine? I dunno? How much fuel does an Abram tank burn?
Getting off topic, but we’ve had 20,000 threads on a lousy charcoal canister. There are bigger fish to fry in my world. Take solace in knowing that you didn’t send an old classic Jaguar to the bone yard in order to be scrapped. See you saved the planet!


The up-shot is that I connected the vapour line from the tank to the inlet side of the canister and then connected a line on the outlet side to the Rochester Valve which simply controls when the vapours are purged from the canister. I connected the switch vacuum hose to the B tit on the top of the throttle body and the purge line to the crank case vent T connector. see photo

I eliminated the other two valves !


I’ve started having positive tank pressure problems recently. Only if car drives a good 45 minutes or more. Note, I have no A/C, so no fuel cooling. Cap whooshes outward quite a bit, even while idling. I can hear pump straining. Shutdown, put cap back on, just sitting 10 minutes will give an outward woosh again.

I inspected my valves at canister, and they seem ok?

But this will be the third time I’ve tried to address this. I’ve decided to forgo my complicated contraption and simply hook tank vent directly to charcoal canister.

With this hookup, it will work exactly like it’s supposed to while running. Only difference is while sitting off, any low postive tank pressure under 2psi (?) will go straight to charcoal canister.

I hope my canister can absorb most of it and not get saturated, i will monitor garage smell after long runs. I still have that alien looking thing above right of tank that is supposed to minimize the amount of vapors to canister.

Just did a 45 minute drive, no woosh from cap. Even after sitting. And no gas smell in garage. I guess next few weeks will be telling.

So if anyone copied my contraption, monitor it!

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Yes, the Benz part that you used created a whoosh sound…not as bad as what I had before, but I just removed it this weekend and put in my old Rochester valve substitute which seems to require little, if any, force to push air through…

If I had to hazard a guess, the solenoid you installed is no longer working the way it should. I would test it, and the 12v power it is expecting.

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Sorry for suggesting it. At the time it all seemed good. Funny you removed yours same weekend as me!

Only reason i tried my contraption was because Rochester valve got plugged up after only 2 years.

I like the idea of NO valves now. But i like using my charcoal canister. Didn’t want to vent everything to atmosphere.

Don’t apologize! I decided to copy you! I am grateful you posted what you did, then came back to share when it stopped working!

Gonna leave the solenoid in, and the Rochester valve should work as a backup/secondary vent while driving….after I reconnect that vacuum line, but that will take minutes.

Tempted to try this – no restriction, so no tank trauma. I have a second charcoal canister on the shelf. If I install both canisters with the Tank and Purge hoses in parallel, I can double the charcoal capacity. A highway drive should be able to clear them both out.

I have my charcoal canister plumbed with throttle tap vacuum to a valve to open it, and both throttle tap vacuums to vacate it. So only when opening throttle will it pass fumes into the throttle bodies to be burned. Never at idle.

So far two days driving with straight connection from tank to charcoal canister, i smell no gas coming from canister after parking. Big test will be parking in hot sun. May have to wait a few months here in Seattle area!

Beauty is, no positive or negative tank pressure now.

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I’m about there with you. Will also post about offending fuel smells when it gets warm here in DC…which will be much sooner than you!

Is there a difference between the two LH throttle-body top vacuum connectors? Planning to keep using the port vacuum there as the purge trigger, same as yours.

That’s an interesting experiment.

I have been mulling over what to do with my purge system as well, and I had a thought similar to what Greg has now done with his.

It seemed to me that the Rochester valve, and our various multi-valve solutions, only prevent air/vapor going into/out of the tank when pressure is less than 2psi. My thought was essentially: why are we concerned with preventing venting at 1 psi or 0.5 psi? I’d imagine the amount of vapor at lower pressure would be less than the amount of vapor at higher pressure.

If an open vent line to the canister does permit too much vapor over long periods of time at very low pressure, then why not just a pair of 2psi valves, plumbed in parallel but in opposing directions (I don’t know of any single valves that open in both directions at 2psi, then again I haven’t yet looked that much). My thinking is that the engine at idle pulls way more than -2psi of vacuum and that would be sufficient to open the “from tank” valve. That would eliminate the need for any electrical switches or vacuum actuation. But I’m also wondering if this arrangement could put too much load on the fuel pump during the times where tank air pressure is -2psi < X < 2 psi.

Anyhow, curious what everyone thinks, and I’m interested to see how Greg’s “open line to canister” setup fares. (Haven’t been avle to test on my car as the fuel system is undergoing hose replacement bit by bit as I get time through the week)

If I get what you’re saying, I don’t think that will work. All you’re doing is replacing the Rochester valve with a one way 2psi valve, which won’t open until the tank has greater than 2psi vacuum. You don’t want your tank to have any negative pressure. Not good for the fuel pump.

The Rochester valve is what you’re looking for. It opens both ways at 2psi (or is it 3), and then opens all the way with any vacuum applied to it via the third port. But yeah, it is unreliable.

Kirby did mention in the book a possible solution, of putting a filter on both sides of it so it doesn’t get clogged up with gunk. That was going to be my next solution, but I finally got tired of dealing with it.

Once you are able, I would simply connect the vent line to charcoal canister like mine and test it yourself over time. It’s super easy, and very easy to plumb back in the Rochester valve if it doesn’t work out.

The ultimate solution is to get a gas cap that vents. But I don’t want to do that.

That might be an ultimate solution to fuel smell in the boot, but is that a solution to the gasoline vapors?

Would a vacuum reservoir, with a periodic release valve (periodic release timing needed is ???) which puts a periodic vacuum on the charcoal cannister when the engine is not running, and with the tank plumbed directly to the cannister, serve to draw the vapors (thus the smell) into the vacuum cannister?

After that, it gets complicated. :grinning: (keeping the vacuum reservoir charged to last long periods of storage)