Okay...OBDI, 3.9....I'm NOT worried about emissions and all that crap...But I'm hearing that I HAVE to run the charcoal canister on the vent side of my fuel system....I know I'll trip the ecu if I don't (and I'm sure I can fool the system not to), but other than that what's the problem running the vent straight to the plenum? The cell I'm running has a check valve at the tank/vent, so during the inevitable roll-over, I won't/shouldn't dump fuel into the plenum.

By fitzing with the canister, it appears that there is a check valve/blow-off, associated with it...Is it actuated by the ecu? Is it really necessary?

Originally posted by RockRover
what's the problem running the vent straight to the plenum? [/B]
If there is a back fire what prevents the fumes in the line acting as a fuse to the tank

Originally posted by RockRover
By fitzing with the canister, it appears that there is a check valve/blow-off, associated with it...Is it actuated by the ecu? Is it really necessary? [/B]

See first response:flipoff2:

yep. Does more than keep the smell down. If it is clogged, a lower mile one from a yard will do fine.

j

OOOh, wow, this is ironic. I have been dealing with the charcoal canister question for a little while yesterday.

Here's my scenario:

I have a factory Jeep TJ filler neck on the crewcab. I have the standard vent return to the filler which has a check flap that seals *very* tightly.

I am trying to fill a fuel tank that I truly believe can hold approx. 36 gallons. I am only able to fit between 15-17 gallons. This was on the trip home from Paso, we ran it bone dry accidentally twice, so I know how much I'm getting in there.

Cooper suggested that I take a T-fitting and plumb it in-line with the fuel tank vent. He said there were several things I could do with that additional vent line.

1. Plumb it straight to the carburettor

2. Plumb it to a charcoal canister

3. Plumb it to a K&N filter

I went to the aeroquip dealer yesterday and got my fittings. The vent hose from the tank to the filler is 5/8ths line, so my T-fitting is 5/8ths on all 3 sides.

Can I make my third vent line smaller than the main line? I was thinking 5/8ths is awfully large for a little vent line. :confused:

After listening to the pros/cons (mostly cons) of plumbing to the plenum, I'm wondering if I might have the same concerns plumbing straight to the vaccum port on the carburettor? (Q-jet)

I haven't hacked into the vent line yet, I was thinking of going to the Heep dealer and seeing what kind of a factory setup they run with the TJ's.

I do happen to have a charcoal filter from my '90 RR I can use if I need to.

Thoughts? Ideas? Warnings? :flipoff2's:????

Why even bother with a sealed system?

Ron

Originally posted by evilfij
Why even bother with a sealed system?

Ron

I dunno. :confused:

Maybe you can help by showing the virtues of a non-sealed system. ;)

Truly, I don't know, 'cept it might be easier to run a non-sealed system.

Originally posted by evilfij
Why even bother with a sealed system?

Ron

It's called tread lightly on the air. :rolleyes:

Originally posted by Old Scout


It's called tread lightly on the air. :rolleyes:

Evaporation is one the MAIN sources of polution. There's a reason why there are sensors on tank pressure for this. You can run to the carb, but I would only do so if you have a mixture control on the carb. You are essentially going to be pre-charging the mixture and running rich under some conditions.

j

So basically the main reason not to is polution.

Reasons for: simple, cheap, easy, idiot proof, less to break etc.

Ron

Maybe you can come to your own conclusion from this description. I say pull it. It shouldnt throw a check engine light. the Comp is to stupid on your year truck doug.

EMISSION CONTROL

EVAPORATIVE EMISSION CONTROL SYSTEM

The system is designed to prevent harmful fuel vapour
from escaping to the atmosphere. The system
consists of a vapour separator tank, connected to the
fuel tank and located between the body inner and
outer panels on the right hand side of the vehicle near
the rear wheel arch. An Evaporative Emissions
(EVAP) canister, containing activated charcoal, is
positioned in the engine compartment attached to the
front right valance. The two components are
connected by a pipe running the length of the chassis.

A pressure relief valve is fitted in the hose which is
open to atmosphere. This valve acts as a safety valve
should a build-up of pressure occur in the system, for
example if a hose became blocked or kinked. The
volume of vapour emitted, in such an instance, would
be limited.
A pressure relief valve is also fitted in the hose
connected to the adsorption canister and releases
vapour to the canister when the pressure in the
separator reaches between 5 and 7 Kpa (0.7 and 1.0
lbf/in 2 ).
In the top of the separator a shut-off valve is
incorporated in the vapour exit port to prevent the
possible presence of any liquid fuel being transmitted
to the EVAP canister should the vehicle roll over.
The EVAP canister, which is connected by a hose to
the plenum chamber, absorbs and stores the fuel
vapour from the fuel tank while the engine is not
running. When the engine is started, the vapour is
purged from the canister by air drawn through an
orifice in the base of the canister and by the influence
of vacuum at the top. The vapour drawn into the
plenum chamber through a solenoid operated purge
valve is finally burnt in the combustion chambers.
The purge valve, which is attached to the EVAP
canister support bracket, is controlled by the Engine
Control Module ECM which determines the optimum
time at which purging should take place. This will
normally be at engine speeds above idle and when
the vehicle is in motion. A signal from the ECM to the
purge valve operates the solenoid and opens the
valve to purge the canister of fuel vapour.

Originally posted by Old Scout

If there is a back fire what prevents the fumes in the line acting as a fuse to the tank



See first response:flipoff2:

So what's preventing the vent line from the canister to the plenum from becoming a fuse? If there isn't enough gas fumes after the cansiter, then why is it vented to the plenum?

I wouldn't think there would be enough air/vapor in the vent line to make the tank explode...What the heck did manufactures do prior to charcoal canister requirements?

How about venting to the atmosphere? Yea, yea yea...Polution and all that...Maybe I'll worry about it when gas stations here start using fume collectors on their filler hoses...I'm not really worried about my 5-6 x's per month use of my rig distroying the atmosphere.

Plug the plenum intake and put a pcv/check valve/filter on the vent line and call it good?????

I still don't think I heard an answer...Do I need to run the canister?

Ok Doug here is what i would do. Run a line from your tank check valve to a T fitting near the back of the truck. use the original purge valve to atmosphere off the perpendicular side of the T, and let that purge to atmosphere. Now run a small length of hose to the original pop off (inline near the vapor catch at the back of the truck) valve, and then on up to the engine bay. On your truck I beleive the electronic purge valve is not attached to the charcoal canister. if so, plumb this inline with the hose you ran, and then run a hose to the original plenum fitting. A flow check valve(one way valve) may be nice between the plenum and the purge valve. this should be fairly legal, and it will most likely operate just fine without any check engine lights or fire hazards.

the atmosphere valve keeps excess build up out of the system, and is set at a relatively high pressure. the other valve near the tank, going to the engine bay, pops off when pressure gets high enough to purge to the char canister, or in this case the volume in the line. And then the electronic purge valve will finally release the pressure into the plenum once the pressure is high enough in the lines and the comp, knows the engine is running and at a high RPM. . the only problem i see is that the electronic purge valve will be popping of quite a bit. but it should not cause a problem.

So Dump the canister. the above is what I would do if i wanted to Be PC about the whole thing. If not, just vent into the surrounding enviroment like I do with the MOG (carburated though)

Don't forget that heat will effect expansion/evaporation. Other than that, I agree with you rockrover. I have only seen one clog from excessive fumes. All others I have seen fail have been from over filling.

And y'all are correct about hotwire, if that is on that year of truck. It ain't that smart.

j

In a high ambient temperature situation (Moab for example) could the amount of fuel vaporizing and entering the plenum with no control adversely affect one's air/fuel mixture?

In the distant past, I regularly disconnected them from hot rods I built and did little to nothing with the vent in the engine compartment. The canisters can be used to make nifty fuel line coolers too!

Paul

RockRover,

I didn't mean to hijack your thread, but it was just weird that you were thinking about the same exact thing I was thinking about.

Personally I think I'm going to go to the Jeep dealer and try to emulate a factory TJ setup. I'm not so much concerned about the PC-ness of the thing, I just need the filler neck to work as advertised and I think that this will be the ticket.

For you? I'd say you should "Plug the plenum intake and put a pcv/check valve/filter on the vent line and call it good". (Your quote BTW...) :flipoff2:

Let us know how yours turns out, you may have some sage advice for the rest of us.

Originally posted by PTSchram
In a high ambient temperature situation (Moab for example) could the amount of fuel vaporizing and entering the plenum with no control adversely affect one's air/fuel mixture?

Paul
Carb'd yes. EFI/TBI no

j

Okay...Thanks for the info Puff (still hard to get used to calling you Puff...)

The electronic purge is on top of the canister, but it pops' off relativly easy.

So what I think your saying is simply remove the elec. purge, let it vent w/o the canister, and run the same line to the plenum (off the purge). The only thing I worry about that is the issue of the plenum sucking dust when the purge valve opens via the ecu. I could put a in-line filter, but that's a pia.

One thing to remember in my case is the fact I'm running a Jeg's fuel cell with none of the filler neck and vent components that came with the stock tank (don't know what it's called, but it's the "black-box" on the right side frame-rail near the filler neck...Not sure if that's in the equation as well, but...

I'm thinking I'm just going to cap the plenum, and let the vent line vent outside the rig near the rear of the vehicle. If it's too stinky then I'll figure out something.

Either that or I'll just mount that big assed canister back under the wing were it came from....:P

--D

ooooh! Can I get that purge valve? Mine is having some issues with staying open! Otherwise, anyone know where I can pick one up without the whole assembly?

What's the problem with it staying open?

A check engine light for the rest of my life! I already got the ABS and sometimes my parking break flikers. Its a freaking christmas tree on my dash and I'm a jew!:flipoff2: