Max_5gen

iTrader: (2)

You do realize that the pressure is supposed to be NEGATIVE, don't you? This way if there's a leak in the system to atmosphere it won't let fumes escape until leak becomes big enough ...

Another thing which might prevent you from fooling ECU completely is the algorithm might not be so simple - ECU could check the pressure before engine start and after and trigger CEL if it doesn't drop fast enough. Or open/close some valve and monitor pressure signal. What FSM states is probably related to certain stationary conditions but it doesn't mean that's all ECU cares about.

I also have feeling that by the time you manage to fool ECU you'd become an expert on EVAP system internals and will be able to fix it the right way as it might turn to be simpler .

BlackMacks

iTrader: (3)

Thanks, Max, for the discourse, but in my reading, the pressure sensor does not have a suitable voltage output for negative "pressure", it simply starts at atmospheric and increases from there.

I think that makes sense, as the fumes that build up in the sealed system would indeed create pressure, which is released by the control solenoid acting on the purge valve. The control solenoid gets its power signal from the ECM, acting on the voltage signal from the pressure sensor. Low/no pressure=no power to control solenoid=no action of the purge valve. High pressure=power to control solenoid=purge valve opens, and the process is repeated as needed. I haven't found any further info on the action of this system, as far as fail-safes or start-ups go, it's a fairly simple system. It's not always pressurized, cold gas doesn't create fumes or expand, so pressure isn't always existant in the system, merely during the appropriate conditions.

I know what will fix my EVAP system, my purge valve has failed, and as everyone knows, the mounting bolts snap off in the canister meaning you have to buy both, which I just don't care to do. I'd rather this cheap simple easy fix than the alternative.

Worst case scenario, you're right, and I end up having to buy parts. I can try this first, for free, and it's reversible, so why not give it a try.

Max_5gen

iTrader: (2)

That's not what FSM says about it:

BlackMacks

iTrader: (3)

Robert, I've come across something that's got me thinking my original idea isn't gonna work, unless you've got some other news.

I was plugged into my scanner the other day, checking engine parameters and data readouts, and I noticed that my EVAP pin at the ECM was reading 3.4V, tho I can't understand how, I know my system is compromised. I'm gonna try reading up a bit more on the system and see if I can figure it out.

Rochester

iTrader: (3)

My EVAP system is throwing a code... the purge valve is stuck open back at the tank. Up until now, I thought the solenoid under the hood was the only valve. Go figure.

It's kind of ironic. Here I am saying "leave it alone", and yet next week I'm going to be spending money on an EVAP repair.

Guess I deserved that.

BlackMacks

iTrader: (3)

lol, neener neener neener.....

I'm just messing with ya, John, it seems that purge valve back at the cannister is a common failure item. Surely it's location at the rear wheel well plays into it

From what I can tell, the purge valve is operated by the control solenoid under the hood. The solenoid under the hood receives it's power/no-power signal from the ECM, and then forwards that signal to the purge valve. The ECM gets that signal from the voltage generated by the system pressure valve, and the cycle continues, as long as the voltage signal from the pressure sensor is between expected parameters. When it's not, CEL. At least, that's what I thought initially, but I'm doubting that here lately.

Sure, replacing both the valve and cannister will fix our problems, I'm just aggravated at the prospect of shelling out that kinda dough on a system I'm not concerned with preserving. Fixing it's currently not that high on my priority list, truth be told.....

Rochester

iTrader: (3)

I'm not even going to bother trying. Let my mechanic deal with it, which of course adds to that cost. He's not planning on replacing the cannister, just the purge valve.. which runs $100 give or take, plus labor cost.

Any way you look at it, though, I'm spending money to fix a system designed to have a positive environmental impact by virtue of it's use in every single car. I suppose I'm OK with accepting that cost up front in the purchase price of the car, but feel kind of put out having to continue paying for that intent once the original system fails.

Kind of like paying taxes on a tax refund, know what I mean?

Rochester

iTrader: (3)

...and it seems my charcoal tank is cracked. So now, in addition to the $100 purge valve and labor costs, pile on another $200 for the filter tank. Believe me, this situation occurring right now, in light of this thread discussion... well, I'm keenly aware of the irony. But I have to have it fixed. I can't have a full-on SES masking future SES issues.

So, crap. Crap, crap, crap... I just spent a fortune to fix this damn EVAP system.

Who wants to be the first one to say, "I told you so!"?


[edit] Another phone call, and my mechanic is going to try and save the box, seal the crack and strap the box tight with massive zip-ties... then check for leaks. If it works, that's $200 I don't have to part with. The whole thing still sucks, though.

BlackMacks

iTrader: (3)

John, I'm trying so hard to stifle a side busting belly laugh right now

kidding, of course. I had typed up a reply to your previous post, talking about how most of the org'ers I read about, never _intended_ on replacing the more expensive charcoal can, with their purge valve, it just so happened to work out that way, but the server dropped, or my connection, or something, so I lost it and didn't feel like re-typing it all.

But you're living the exact beef I have, and my exact intent, behind going around the system, rather than through it. I just know that the purge valve isn't gonna be it, I'm gonna, like you, have to shell out a few hundred extra bucks (that could have been spent on much more "useful" things, imo), to get this stupid CEL to go out.

And before the "junkyard'ers" start clamoring, man, y'all, really, and I'm one of the first to go salvage yard diving, but there are certain things that I'm just not gonna waste my time or money getting from a salvage yard. A 100k+ mile plastic box that's almost 10 yrs old is right up there at the top of the list, it's just as likely to be bad, or go bad right away, as my currently failed parts are. That's why I'd buy these items new, if I were to.

I'm not exactly a card carrying member of greenpeace, but I'm loosely aware of, and somewhat concerned with environmental crap. But I'm not so concerned that I'm willing to shell out $2-300 bucks on this mess.

Rochester

iTrader: (3)

Go right ahead and enjoy the irony, BlackMacks. It is frustratingly funny.

And I don't confuse pride with helplessness, so I'm OK.

I appreciate the sympathetic mind set. I get it.

trooplewis

iTrader: (1)

Seems like a little 5-minute epoxy would be the fix for a cracked canister, maybe hold it in place with the big zip ties while it dries. Isn't there another solution that would allow it to remain 'broken' but not throw a code? i.e. like the O2 simulators, just ground the appropriate wire in the sensor?

BlackMacks

iTrader: (3)

Troop- I had been reading up on the operation of the evap system, and RobertC and I have been loosely exchanging ideas on how to leave the system broke but fix the tattle tale.

But then my blower motor went out, and my radiator's had it, so since my sticker isn't out till year's end, it went on the back burner for me. I'm not sure if Robert's had any luck fooling the ECM or not.

It appears that my original idea will not work, but again, I'll get back to this later down the road.

Nopike

iTrader: (2)

Not sure if anyone answered this....... it vented those fumes into the air we breathe. That is the main reason for the EVAP system, to reduce air pollution.

BlackMacks

iTrader: (3)

Max, you're absolutely right, I'm an idiot, yet again overthinking (or in this case, not thinking enough) about the operation of the EVAP system. Robert, you're (and me) gonna wanna pull a vacuum on the pressure sensor. Looks like about -1.5 psi oughta do the trick. That should reduce the voltage at ECM terminal 60 so that the system appears without leaks.

Apparently, when the system's just hanging out at atmospheric, the sensor's sending that 3.4V signal to the ECM. Only when the system's able to hold a vacuum does the signal decrease, and the ECM thinks everything's functioning as normal.

So, NOW, I've got a plan, lol. Grab a one-way valve and a hand vacuum/pressure pump, pull about -1.5 psi, cap it, clear the codes, drive around a bit, and see what we get. You guys are the best

Max_5gen

iTrader: (2)

There's simpler solution to this - remove pressure sensor altogether and replace it with resistor of such value to produce necessary voltage to the ECU. You can measure your sensor to get an idea of the resistor's value.

I'm still skeptical this would work as ECU might be looking for a change in the sensor's output based on what it's doing with the engine. Worth a try I guess,

sontakke

I suspect that is exactly what ECU would do. Those Mode $6 tests (and Mode $9 Bi-directional tests) generally initiate a specific test when certain pre-conditions are met. A resistor probably will not cut it. What *might* work is to jury rig something which will prevent the evap test from ever being carried out. This means your inspection monitors will never be fully completed but you do get one waiver, so that would be OK. The evap test only runs when the gas tank is neither full nor empty. One might be able to fool ECM by appropriately overriding that signal. I believe evap test will run only if the gas tank is over 1/4 but under 3/4.

- Vikas

Rochester

iTrader: (3)

Got my car back just now. The crack in the tank was only in the thick plastic area around the valve, and didn't actually compromise the rest of the tank... so it turns out the tank is fine. What it did compromise was getting the valve secured, but 2 monsterously beefy zip-ties took care of that.

In the end, I still spent more money on this thing with no return value except clearing a SES. But I also spent far less than it could have been if I had taken it to the dealership.

RobertColianni

Sorry for dropping off the face of the Earth this past week. I've been working a ton of hours and the forums were telling me that some malware crap was asking for permission to operate when I'd open the User CP link.
Today is my birthday and I have work like every other American, but I'm ordering some more equipment in order to make my car more invigorating to drive and will chime in when ready.

Rochester

iTrader: (3)

2 days later, and the SES is back on again. This time it's not the release valve (because that's new), it's whatever code that says I have a small leak.

So before going after this ******* expensive charcoal tank, I bought a new OEM gas cap ($23) and cleared the codes.

What a trip.

I30driver

I removed my evap canister and in the process snapped off one of the mounting bolts so I will have to drill that out and tap it. Then while trying to remove the valve those mounting bolts both snapped off (of course). This whole thing has been a nightmare and I highly recommend going to the dealer for any evap leak (after checking the gas cap). Unfortunately it seems like Nissan guaranteed themselves some repeat dealer repair business with this design.

Chris Gregg

iTrader: (59)

Gas cap fixed the code up until two days ago. Tried to retighten the cap and had code cleared...still there. Yes, that little light is very frustrating...especially when you know there's nothing really wrong....

I'm interested if anyone has gained any further progress on this issue.

Which component is it that is supposedly broken with the code 455 (high vacuum leak)? I don't suspect the sensor itself (25085p). So, is it 14920+A or is it 14920+B? They are both vavle control assemblies.

Rochester

iTrader: (3)

Next Wednesday, my car goes back to the mechanic for this problem all over again. This time he'll be hooking up the smoke machine to find the leak... even though we both know it's the hairline crack at the charcoal tank where the new release valve was installed.

In other words, spread cheeks, insert EVAP tank. Smile and say, thank you may I have another?

BlackMacks

iTrader: (3)

Well, John, you'd be happy to know I channeled my inner nature lover , and replaced my cannister vent valve earlier today. Same problems everyone else related: my bolts' heads snapped off, and I discovered a crack in my tank next to one of the bolts, but upon closer inspection, the crack was superficial, so I didn't worry, and I secured my valve to my cannister using large zipties like everyone else.

I went for a decent drive on lunch, curious as to whether or not my codes would go away on their own, then came back and plugged the solus in- codes still there, along with an 02 sensor code. So I cleared all 4 of 'em and will drive it a little tonight, see which ones come back.....

I've still got my one-way vacuum valve idea ready to try, if my new vent valve doesn't do the trick due to something more expensive needing replacing. I would just soo much rather spend my limited budget on other things

Rochester

iTrader: (3)

Happy? No... commiserative, perhaps, but not happy.

If you're truly following me down this crappy road, you'll be getting a "small leak" code in about 30 miles. We cleared it, I bought a new gas cap, and it showed up again in another 30 miles (give or take).

*sigh*

BlackMacks

iTrader: (3)

Just as sure as I'm typing this, I'm jinxing myself, Roch, so ya know, but I figured I'd share my weekend developments, for whatever they're worth:

After clearing my EVAP code Sat. night, I did a bit of driving that evening, and more Sunday, to the tune of well over 100 miles, stop-n-go all of 'em, multiple shutoff and restarts between trips. In other words, plenty of time for the ECM's "readiness check" to complete.

And still no CEL on as of this morning's commute to work, not even for the lazy O2 sensor I know I've got on bank one, sensor two.

Maybe sometimes it is as easy as replacing the faulty part?

And Maybe Sometimes a cigar is just a cigar. Not right now it isn't... but sometimes.

Rochester

iTrader: (3)

Lucky SOB.

I'll be looking for closure to my EVAP woes mid-week.

Prophecy99

iTrader: (1)

im in the same boat and look forward to doing the first step before buying parts. I would like to see pics of these items anyone have any? I mean i saw the fsm diagram but still, picture=1000 words.

blackmack , im still not sure which route you took. your oneway vac vaule, or just removing/replacing the faulty part?

Rochester

iTrader: (3)

To sum up current state: BlackMacks replaced his release valve, has a hairline crack in the charcoal tank, but no longer has any codes. I replaced my release valve and my gas cap, also have a hairline crack in the charcoal tank, and have a small-leak code.

So much for clean living...

Sorry, Prophecy. I don't have any pictures. That, and I use a mechanic for things like this. BlackMacks turns his own wrench, so maybe he'll oblige... if you can get him to crawl under his jacked up car again, that is.

BlackMacks

iTrader: (3)

Proph- I replaced my canister vent valve.

So far, so good (knocks on wood)

John- I did find a crack in my tank, but again, it wasn't in any of the "sealing" walls, it was along that seam that one of the bolts' anchor nuts sits in, so it couldn't appear to be able to contribute to any leak.

I think I could shoot a pic or two after work, if it helps.

Clashez

iTrader: (5)

Rochester
You got to look at the Bright side of things, it could all way turn out worst.
you would think as long as you been a member and all the reading up you probably do you would turn your own wenches. and save up some money for some custom maxima headers lol jk jk

Rochester

iTrader: (3)

That's always true, yes. Better the devil you know...

Yeah, but I don't clean my own gutters, either. Let someone else get up on that ladder.

LOL indeed. I'd be willing to bet my Cattman Y-pipe provides the same gains or better than a modified-to-fit set of CM shorty-headers. I'd also bet my Cattman y-pipe would last longer, and bolt right up perfect.

Clashez

iTrader: (5)

I was thinking about getting the catt man y-pipe.
Before i got this car from my dad the original owner he just put in new pre catts ,i wonder if the headers would be worth the hassle I really dont want to throw any code or my car to run rich

Rochester

iTrader: (3)

On the 5.5 gen, Catt's Y-pipe is not a significant cost-to-value power mod. And to maximize the configuration, you'd need to match it with a good cat-back.

All mods are incremental, Clash. Start with a cat-back, and work your way forward as budget, research and experience allows.

Chris Gregg

iTrader: (59)

Just to get some additional insight, I went ahead and contacted Aaron about his experience with the system. Here is what he had to offer.

"Chris,

I don't know of a way to trick the ECU into thinking it still has a functioning EVAP system. I never researched it myself so I don't know what exactly triggers the CEL.

I removed my EVAP system completely, so I have a code stored. I am not effected by emissions, so it's not a problem for me since I have a 1992 Maxima converted to OBDII.

Sorry I couldn't be of any help.

Aaron Kimball
www.NWPEngineering.com"

So, it was worth a shot. Thanks again, Aaron (For all you do)!

Prophecy99

iTrader: (1)

Thanks chris, worth a shot for sure. This seems like a really common thing as our gen is aging.

Rochester

iTrader: (3)

It's been a few weeks since I unhappily joined the Evap Club, and hundreds of dollars out-of-pocket, as well as the inconvenience... but it seems my journey has ended. I have a new release valve, and now I have a new tank. No more SES.

Here's a picture of the old tank.



And here's a close-up of the crack, somewhat widened from its original state. As you can see, it looks like the crack only compromised the plastic supporting the bolt. But as it turned out, it ran deeper and was the source of the small leak. Smoke test confirmed it.



I swear, these things are designed to fail when corroded. Really stoopid design.

And there are certainly better things to be spending car-money on. I'm just glad this is over.

BlackMacks

iTrader: (3)

Oh snap! That's EXACTLY where my tank cracked, but not that severe......

and John, you'll appreciate the kharma: my CEL popped back on the other night, I'll pull codes in a bit

It better be that lazy O2 I've got, swear if it's that small leak BS I'mma

Rochester

iTrader: (3)

The SES is back? Oh boy...

Although I had this work done at my mechanic's, I also spoke to my local dealership about the problem. They said they used to try and replace just the valve years ago, but have since given up. Now, whenever someone has a bad valve code (stuck open or stuck closed), they replace the tank, too, because it's a certainty the bolt hole will crack... particularly in this northeast climate.

Like I said, this is a poor design. Consumers are paying twice for it. (Well, you're not paying twice, I am. But that's only because I'm an original owner.)

Prophecy99

iTrader: (1)

Keep us posted
Thanks for the pictures. After seeing the pictures I was thinking of torching the plastic back shut, but as u described the crack was a lot deeper that it appears. Next question what was the price for the tank?
And if I am reading the dealership diagnostic right, you still need to replace the valve additionally?

And just so I am on the right page would it be a good try to replace the gas gap first?

Heres a dated post I found too

from this
http://forums.maxima.org/5th-generat...ure-check.html

Rochester

iTrader: (3)

Prophecy, I don't have the exact codes off-hand, but if you have a small leak code, start with the gas cap. (about $23)

If you have a valve stuck open/closed code, you'll have to replace the release valve at the charcoal tank. (about $100)

However, replacing that valve will likely destroy the charcoal tank, so you'll have to replace that as well. (about $200)

Figure 1 - 2 hours labor for the shop, and you can approximate the math.

With hindsight, if there were someway to cut the valve bolts, rather than attempt to back them out, you could then strap the new valve in against the tank. There's an o-ring on the valve that makes the seal. After which, all you really need is some technique to fix the valve tight... it doesn't have to be the OEM bolts. Be creative, maybe you can get lucky.