Charcoal Canister / LRA Breather Fix (1 Viewer)

[TeCKis300]

TL;DR​

1) LRA charcoal breather plumbing and adapters are too small in diameter, limiting venting when filling the main tank tripping the gas pump. Needs 5/8" ID plumbing though to breather.
2) Breather filter is a maintenance item. Too much dust and dirt will plug the external breather filter, blocking the vent and main tank from taking gas.
Solution: Change breather hose to 5/8" and use a large 5/8" breather filter. Clean breather filter every 25k miles, or when gas fill speed become sensitive. More detail here

Symptoms:​

This has been awhile in the making, with a slow degradation to where things sit now. There's been a number of related and peripherally related threads and my hope is to finally shed light on these issues, and provide insight into potential fixes. While this is focused on the LRA tank, understand that these charcoal canister issues can effect higher mileage stock cruisers in the same manner. Research shows other makes and models also experience these issues, accelerated when a vehicle is exposed to more dirt, silt, and off-road.

1) Slow LRA main tank fill
2) Degraded main tank fill bordering on tank not taking fuel
3) EVAP CELs

Findings:​

Breather area gets pretty dirty.

Yup, breather is completely caked and plugged.

Hrmm, didn't think much of this setup when I installed, but why would a stock 3/4" breather line get necked down to less than 1/4" ID in parts?

 

[TeCKis300]

Fix​

Discussing with @wardharris from LRA, two strategies to fix this. Ultimately, this perhaps is a maintenance item to clean the breather filter, especially if one off-roads a lot. Non-modified cruisers that experience this at higher miles may need to clean or replace the inline Charcoal Canister Filter.

1) Extend and relocate breather to underhood, where the air is much cleaner​

This is probably the longer term fix, but I choose to do #2 below. Plumb a large diameter 5/8" fuel/vapor safe hose to under the bonnet. Locate the breather there as far away from hot items (i.e. exhaust manifold) as reasonable. There was some discussion about tapping the airbox to draw clean air from there, but re-thinking that, it's prob not a great idea as the breather wasn't designed for what would be vacuum there when the vehicle is running.

Parts:
Amazon product ASIN B07G3HT7CJAmazon product ASIN B000CRDKVCAmazon.com: K&N Vent Air Filter/ Breather: High Performance, Premium, Washable, Replacement Engine Filter: Filter Height: 1.5 In, Flange Length: 1 In, Shape: Breather, 62-1020: Automotive - https://www.amazon.com/gp/product/B000BR1QKU

​

2) Improve the breather at filler location for longer service​

Charcoal canister filter > 5/8" line > New cone filter

I'm going to try this strategy with a larger surface area breather, and larger diameter tube plumbing to enhance the ease of fill. With a mushroom filter that has vertical sides elements that doesn't encourage dirt to lie on the surface media. It's ultimately going to require more periodic service here but I'm going to give it a try and see. If it works well to address slow fill, I may extend it to the engine bay in the future. I'm also going to install back the OEM inline charcoal canister filter, for 2 levels of filtration.

I used pressured air to blow out the charcoal canister by way of the connection ahead of it to the main tank. Fortunately the charcoal canister was not gunked up with silt as very little if anything blew out. I think the root of the issue is simply the breather filter completely plugged up.

Pretty much same parts are going to be used for this fix option just with a shorter segment of 5/8" hose, clear through to the breather to remove all the small ID adapters that create the separate slow fill issue of the main tank.

Parts:

Amazon.com: ICT Billet 5/8" to 3/4" Inch Hose Barb Splice Coupler Reducer Repair Fitting Adapter Connector Radiator Coolant Intercooler Heat Exchanger Fluid Designed & Manufactured in USA Bare Aluminum AN627-11A: Automotive

Buy ICT Billet 5/8" to 3/4" Inch Hose Barb Splice Coupler Reducer Repair Fitting Adapter Connector Radiator Coolant Intercooler Heat Exchanger Fluid Designed & Manufactured in USA Bare Aluminum AN627-11A: Intake Manifolds - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

https://www.amazon.com/Fuel-Line-Hose-Small-Engines/dp/B07YBDKK9T

https://www.amazon.com/gp/product/B000BR1QKU

Cleaned up and fixed here

3) Clearing Evap CELs
With modern cars, this is an important capability to have, and skills or devices to reset this should be a part of the recovery toolbox. Likely because federal mandates, dumb emissions CELs lead to significant impacts of the vehicles operation. This can happen at inopportune times when least expected... as it happened to me 50miles in the middle of Death Valley after a nights sleep boondocking with my family in tow. Causing my LX to be stuck with flashing Christmas lights the next morning and without the ability to switch between 4Lo/Hi or CDL. Unfortunately, I needed to travel 20 miles of technical trails that morning. Fortunately, I was already in 4Lo from the night before. Of course, my laptop that woked with the OBD-II cable I had on hand discharged overnight as I didn't shut it down properly. I decided to travel further closer to civilization stuck in this mode, before trying to resolve it just in case.

Most basic way to clear is to pull the battery for a few minutes which is what I resorted to.

Most expeditious way is to have an BT OBD-II reader with App (I use Car Scanner on Android), and I can clear this in under a minute.

https://www.amazon.com/gp/product/B00H9S71LW

 

[TeCKis300]

Analysis​

Thanks @grinchy for conveniently posting this pic below while I composed this writeup!

Plugged Charcoal Canister Vent Filter​

The charcoal canister has a normally open vent that is plumbed to atmosphere. It serves two functions 1) Draws air into the main tank to equalize as fuel is drawn down 2) Vents air out from the main tank as it is being filled with gas. This vent from the main tank is a secondary large diameter tube path by way of the charcoal canister to atmosphere.

This charcoal canister vent is plumbed in stock form to atmosphere even if it may look like it's plumbed into the filler neck. It's a sneaky plastic collar that helps it breath from the semi-enclosed (and cleaner air) zone in the filler door. Versus the LRA setup that uses an aftermarket breather filter tucked high behind the filler neck area.

The problem arises over time with dirt/silt. The stock setup is remarkedly simple yet effective at managing dirt. It has an internal filter that blocks fine dust from reaching the vent valve. The LRA setup breathing dirty air from behind seems to be much more prone to dirt dust clogging the cone breather filter, but also potentially contaminating the vent valve at the charcoal canister. The largest clue that this was becoming an issue is the problematic filling at the gas pump where the car really didn't like to take gas in the main tank. Evolving to CELs. This really reared up after my Death Valley trip with over a 100 miles on dusty dirt roads. And seemed to get worse with each subsequent off-road trip to Salton Sea and Lake Powell.

Pics in post #1 confirm the completely blocked breather.

Inadequate LRA Charcoal Canister Vent Line​

This also gives rise to a suspicion I've had with the LRA tank install causing the main tank to be more sensitive to filling. The stock vent is a large diameter 3/4" breather line. In the LRA setup, there's adapters used going from 3/4" to 3/8" to ultimately an adapter to the cone breather filter that has an internal diameter of only 1/4".

Since it's now obvious a plugged vent filter will cause the main tank not to want to take gas, it also logically mean an inadequate vent line can prevent fuel from filling at full bore! I'm unsure if this was by design to limit flow for a reason I don't understand yet, or an oversight, but I do plan to try and resolve this shortcoming.

Evap CEL/DTCs​

Fist of 5 DTCs - P043E, P043F, P2401, P2402, and P4219

From Toyota literature, the combination of the above suggests the following 5 highlighted potential malfunctions. All generally associated with the EVAP systems inability to self test due to clogging. It's clear the cone vent filter is clogged with dirt as a definite issue. Whether there's a deeper issues of the vent valve, leak detection pump, or reference orifice, still remain to be seen. I believe it's primarily in the cone filter.

For more background on the evap self test, it's a pressure test that's typically run in the middle of the night, or when conditions are met. A clogged vent would basically prevent the system to test any pressure behavior. Which is why it's common to see the dash light-up like a Christmas tree the morning after if the systems fails this test. It's unfortunate but the CEL limits major functionality from the car including switch 4Lo/Hi and other major functions - a behavior likely dictated by emissions regulations otherwise people would ignore these.

 

[TeCKis300]

What a Fix Looks like​

Much larger breather inner diameter

Knowing how much dirt the breather is exposed to, I put the OEM filter box back inline as the left of the filler tube. Then ran that line up to the new breather again located at the top. Breather height is important to minimize any potential fuel vapors as they are heavier than atmosphere. Will see how long this lasts? Cleaning/servicing honestly wouldn't be too bad and likely an easy 30 minute job taking off the wheel and plastic liners to access.

 

[grinchy]

a nice run down of how the Toyota version of evap in the 200 and many other Toyotas works

 

[grinchy]

Schematic?

 

[TeCKis300]

Long write-up but it's all there! I'm still in the middle of the fix now waiting for a few parts from Amazon. It's wordy but there's a lot going on. Hopefully this clarifies the problems and helps some others get resolution.

 

[RET2]

Would a small foam wrap-around pre filter help? Similar to ones used on some shop vacs?

 

[TeCKis300]

Would a small foam wrap-around pre filter help? Similar to ones used on some shop vacs?

Surely would and I've been trying to identify one that'll work. A filter sock was recommended by Ward as a possible improvement. If anyone finds one, I'm all ears.

Also considered plumbing air from the fill compartment as the OEM is setup for. Difficulty is that the LRA filler neck doesn't seal as well against the filler neck boot. I find after a rough off-road run, that the boot sits ajar on the neck, reducing the seal, making it no cleaner an area. Also have concerns for SMOG and CA CARB visual inspection so I don't want anything aftermarket looking there.

 

[RET2]

Surely would and I've been trying to identify one that'll work. A filter sock are recommended by Ward could also help. If anyone finds one, I'm all ears.

I'd venture anything that would work would be a one-off. Trick would be to find a source of raw foam and fab a couple up

 

[RET2]

I'd venture anything that would work would be a one-off. Trick would be to find a source of raw foam and fab a couple up

Home depot stocks pre-filters for some of their shop vacs and I would imagine one of those could yield 3 or 4 of the size you need.

 

[CharlieS]

I haven’t looked around but I wonder if there are small prefilters in the dirt bike world that would fit there. Or buy a larger dirt bike air filter prefilter sock and cut it up to make smaller ones?

Looks like you can buy sheets of the material: Outerwears 12 in. x 12 in. Pre-Filter Sheets - WR12BK Dirt Bike Motorcycle Snowmobile | Dennis Kirk - https://www.denniskirk.com/outerwears/pre-filter-sheets-wr12bk.p305420.prd/305420.sku

 

[grinchy]

I recommend putting a liquid prevent /rollover type valve on the LRA vent line at the tank, and then teeing the vent into the emissions evap line BEFORE the canister.

The emissions evap line will take a 5/8" brass barb.

Only purpose of the valve is to prevent fuel creep into the evap canister on an overfill. Could accomplish the same thing by high pointing the vent line to where the current LRA filter is located and then running it down and teeing into the evap line, but I like the valve better as it has utility on it's own merits.

Additionally why not use the stock filter unit? It's already psuedo sealed and wouldn't get the pictured buildup.

 

[TeCKis300]

I recommend putting a liquid prevent /rollover type valve on the LRA vent line at the tank, and then teeing the vent into the emissions evap line BEFORE the canister.

The emissions evap line will take a 5/8" brass barb.

Only purpose of the valve is to prevent fuel creep into the evap canister on an overfill. Could accomplish the same thing by high pointing the vent line to where the current LRA filter is located and then running it down and teeing into the evap line, but I like the valve better as it has utility on it's own merits.

Additionally why not use the stock filter unit? It's already psuedo sealed and wouldn't get the pictured buildup.

Trying to understand the goal of the rollover type valve as I'm having a hard time drawing the picture in my mind? Is that a separate thing you're proposing?

Regarding the stock charcoal canister filter - I don't believe the buildup is so much that the aftermarket cone filter is exposed, rather it's always drawing in air and plugs up over time because of where it's drawing air from. Pretty sure the stock enclosed filter can develop the same problem overtime, just that it breathes from a cleaner source. Mine had ~100k miles of service in the stock config. Blowing compressed air through it, it had a good amount of dirt and dust come out.

 

[grinchy]

Trying to understand the goal of the rollover type valve as I'm having a hard time drawing the picture in my mind? Is that a separate thing you're proposing?

The main tank has a liquid stop valve in it to prevent fuel getting into the evap line. I think it would be required if the vent was to be used as a pseudo evap line to include a similar valve so that the fuel can’t get into the canister in an over fill.

I drew it out but it seems like it’s not an improvement with this routing.

perhaps the ticket would be to tee the vent line and run one side to the filler and the other side tee into the evap line. That would provide a third leg to pressure balance the tanks?

 

[tbisaacs]

No codes but my truck really doesn’t like being filled up. Is this filter behind the wheel well liner and would cleaning it fix that issue?

 

[Wisluggo]

No codes on my truck but I do get an odor of gas near the tank.

 

[CharlieS]

I like your idea of extending the filter to the engine bay. At least then you can keep an eye on it and service it more easily.

I also wonder about the idea of piping the hose to the air filter housing, with the filter inside the housing. That must be a relatively decent source of clean air, especially if you placed it after the air filter.

 

[grinchy]

No codes but my truck really doesn’t like being filled up. Is this filter behind the wheel well liner and would cleaning it fix that issue?

Do you have any fuel mods? If not probably you do need to replace the stock filter, either with the factory part or another similar.

 

[linuxgod]

Nice write-up.

That's a pretty nice (and helpful) DTC table. Is that sourced from the FSM or is it a generic table from teh internetz?

I wonder if simply hitting the filter with compressed air to clean it off suffice to fix this issue?

Semi-related: Your comment about the evap system doing a test overnight makes me think that the flashing CDL light we often get might be a similar overnight test, which is why it happens within 1-2 seconds of vehicle startup. I really wish I understood that system better. It's infrequent enough for me, but if it eventually becomes an issue I will end up taking apart the motor like you did and cleaning it. Now back on topic...