If you look at the charcoal cannister, there is a little short hard plastic tube that goes to the purge valve (it hangs on the side of the cannister clamp). There is an electical connector, then a long piece of formed hard plastic tubing that goes across the front of the engine to the small port directly under the large air hose that connects the MAF to the Plenum. There is a little release button you push to remove the hose from that port. I capped the port and merely rerouted that hose so it wasn't obvious unless someone was really familar with the Rover 4.0 engine. I did not want to block off the outlet of the charcoal cannister, just the input to the plenum.

It is raining heavily right now, I will take pictures soon. I forget who it was but another member had provided this information recently on a post I did regarding P1316. Hope that helps others as well. I was pretty amazed how nasty that port was, but it has been undisturbed for about 16 years now.

 

That hard plastic hose may be the one I always forget to put back on when I clean my throttle body.
I always remember after I start the truck and it runs like crap because of the vacuum leak lol.
Pics would help any confusion.

 

So under this method, where does the gas fume pressure from the fuel tank escape to? If the purge valve is operated will it vent enough without vacuum, or do you need to disconnect the hose at the purge valve from the tank? I look at it as the hose to the plenum is the "output" of the evap vent system, and the plenum sucks it in. Of course, if there are leaks in the evap system you'll have potential for vac leak induced problems.

 

That is a good question Savannah. I am totally experimenting at present (based upon a suggestion from a fellow forum member who said he capped off both end of that tube. I do not recall who told me, but it was on a recent post on here regarding my repetitive but sporadic P1316 code.

Currently it is venting to "atmosphere" right at the front wheel well.

If it becomes a problem, I can always pull the little cap off and reattach that line. That is why I just rerouted it for the time being.

Since it is a positive pressure, I think it will continue to vent, just not into the plenum. There could be some kind of vacumn issue associated with the current tube. It is the original. The clamps at the cannister and the purge valve are both a crimped style and do not want to be easily removed. I do not know if I could just replace that rigid hose with a piece of vacumn tubing of the correct diameter or not, I guess I could.

Does anyone on here know whether it would be an issue other than compliance with anti-pollution laws? It ran really well on my test run and so far is doing fine. I will advise of any issues I encounter.

I am sure curious minds want to know. Maybe Disco Mike can shed some light on this subject?

 

As long as the check engine light is not on no one will ever know.

Of course any modification to the EVAP system or emissions system is against the law, BUT this is the US and we are free to do what we want to our cars, as long as you pass inspection you are not breaking the law.

 

I will report back whether I encounter problems and have to reconnect it or if it does improve how it runs.

That hard plastic hose always struck me as odd. Never like the routing it has.

 

Well, how did they do it in the bad old days? I just worried about putting gas in, never though much about any vent. Would not want some pressure change causing that little hose to become a stream of liquid gasoline...

 

In the "good old days" gas tanks were sealed and the gas cap was vented, when pressure built up inside the gas tank (like when being parked in a hot parking lot all day) the gas cap would vent the vapor to atmosphere.
Now it is vented to the charcoal canister where it is collected and sucked out into the engine.
Will it just vent to atmosphere from there?
I do not know.
But how did they do it on the non AEVAP versions?
Did it just collect in the charcoal canister until it was full?
Does it vet to atmosphere?
I do not know.

 

Mine is the PreAEL with the round charcoal cannister. That cannister has 3 ports, one from the gas tank, one that goes to what I think is the purge valve then on to the plenum, the thrid port is open to atmosphere anyway.

I have never dealt with any that had a charcoal cannister, but this is my first Discovery. I had a 96 Bronco 351, I do not reall it having one. All my others were pretty much classics with 1986 Benz 420SEL and Porsche 928 and Volvo 240DL.

I prefer the older simpler ones compared to the newest design fiascoes.

Slang, sorry to hijack your thread.

After driving it again, I am impressed with the differences it has achieved. Much smoother idle, great throttle response, winds higher in each gear before the automatic shifts to next gear, smooth when I release the throttle. The pickup it has now is actually impresive, I surmise the charcoal cannister or assocaited tubing must have had some sort of vacumn issue.

I plan to run it as is unless a major problem arises. Just wanted to pass the info on to the rest of you fellows. If you are having P1316 issues, you may or may not want to give it a try. That is totally up to you, just sharing my experiences with it.

 

Danny- I like this, thank you. I have been wondering about that very line and the canister also. I'll check this out. Good luck