do i need the EVAP canister purge valve on my 3800 sc swap? if yes, then where does it go on the engine? and where/what do the lines connected to it go to?

Do you absolutely need one? No. Do I recommend you run one? Yes, but only if you are going to leave the stock Fiero charcoal canister installed.

The job of the charcoal canister is to store gasoline vapors generated by the vaporization of gasoline stored in the fuel tank as it is heated by normal engine operation and weather condition changes. The vapors stored in the canister must be purged from time to time during engine operation, otherwise the canister will become saturated. The OE Fiero engines relied on a ported vacuum source in the throttle body to activate the purge flow. The 3800's throttle body has no ported vacuum source as a computer-controlled EVAP purge solenoid was used instead.

Connection is simple. On the EVAP purge valve, you will see two vacuum ports. One is marked "CAN", the other is not marked. The one not marked gets connected to the large vacuum port on the throttle body or any other manifold vacuum port (that does not see boost, if you are using a supercharged engine). The port marked "CAN" gets connected to both vacuum lines coming off the Fiero's charcoal canister that went to the original Fiero engine. You will need to use a vacuum "Tee" connector.

If you don't use the EVAP purge solenoid then you should not leave the charcoal canister installed. But if you remove/disable this system, you can't simply plug the vent line coming off the gas tank - it must be left open so pressure or vacuum cannot build in the tank. However, leaving the vent line "open" could result in gas vapors to be expelled as the fuel is heated which could result in a raw gas smell around the car which may not only be annoying but could also be potentially dangerous. So it is just better to leave the charcoal canister installed and hook up the EVAP purge solenoid. The charcoal canister can be relocated if it is in the way in the stock location. The EVAP purge solenoid can be mounted anywhere, but keep in mind it may click loudly when in operation so you may not want to mount it directly to the firewall between the engine compartment and passenger cabin. I usually mount them to the transmission case or somewhere low on the engine that is not easily seen to clean up the looks of the swap.

-ryan

------------------
7+ years on this same swap -- NO engine or transmission failures...

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

Darth! you could not be more helpful! that's exactly the kind of answer i was looking for. thank you. and i will keep mine. a little extra work but i would most likly be annoyed by the gas smell. thanks again

Darth, good answer.
See also cave, emission.

relocate if EVAP can doesn't fit in stock location now? Yes.
How?

GM mounted the EVAP can to protect for liquid fuel backup in vent line from stuffing gas at fill time.

84-86 has no overflow tank and if EVAP can is mounted to low... siphon is easy and likely then EVAP can is least worry... fire is a main problem.

87-88 with overflow tank is very hard to drown EVAP can anyplace EVAP is mounted. Can siphon but it's allot harder.

If possible, use the stock location. If not, Keep EVAP can above main tank (86 and down) or overflow tank (87-88) and you should be fine. (as long as you don't stuff more gas at fill time...) Maybe in fender has enough room?

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

quote Originally posted by theogre: Darth, good answer. See also cave, emission. relocate if EVAP can doesn't fit in stock location now? Yes. How? GM mounted the EVAP can to protect for liquid fuel backup in vent line from stuffing gas at fill time. 84-86 has no overflow tank and if EVAP can is mounted to low... siphon is easy and likely then EVAP can is least worry... fire is a main problem. 87-88 with overflow tank is very hard to drown EVAP can anyplace EVAP is mounted. Can siphon but it's allot harder. If possible, use the stock location. If not, Keep EVAP can above main tank (86 and down) or overflow tank (87-88) and you should be fine. (as long as you don't stuff more gas at fill time...) Maybe in fender has enough room?

Ogre, you are correct. We should try to prevent liquid fuel from getting into the charcoal canister. However, I find it very difficult for this to happen as it is nearly impossible to completely fill up a Fiero fuel tank, regardless of what year Fiero you have (although I'm still not ruling out the possibility that it could happen). When I've relocated my charcoal canisters, I've always tried to keep them above fuel tank level. On several occasions, I've mounted them inside the right rear wheel well, just ahead of the wheel and below where the surge tank is located on 87-88 models. In order for liquid fuel to get to the canister on Fieros that have that surge tank, fuel would need to fill up the surge tank and I've never seen that happen. There is plenty of room on the right side of the car ahead of the right rear wheel as there is no air induction system on that side.

-ryan

I have a question regarding the 3800sc evap in the Fiero...
According to my 3800 shop manual (which I have been looking at for the past 1.5 hrs trying to figure this out) there are two evap purge valves.
one is called the "evap canister vent valve"
the other is "evap purge solenoid valve"

I assume the purge solenoid valve is the actual valve that opens/closes allowing the venting of the canister. But what the heck does the canister vent valve do? Are they both needed?

quote Originally posted by ALJR: I have a question regarding the 3800sc evap in the Fiero... According to my 3800 shop manual (which I have been looking at for the past 1.5 hrs trying to figure this out) there are two evap purge valves. one is called the "evap canister vent valve" the other is "evap purge solenoid valve" I assume the purge solenoid valve is the actual valve that opens/closes allowing the venting of the canister. But what the heck does the canister vent valve do? Are they both needed?

The purge solenoid valve is the only one you need to install. It will function as-needed once the PCM has been "properly" programmed for a Fiero swap environment.

In short, the vent valve was used to allow air back into the tank after the OBD2 PCMs ran some diagnostic tests to check for system leaks (among other things). But unless you are going to install the fuel tank pressure sensor as well as the fuel level sensor (from the donor 3800 car), these diagnostic tests won't run. And since most people don't install these extra devices into the Fiero's fuel system during a swap, there's no point in installing the VENT solenoid valve since the PCM won't correctly operate it without these other sensors present and working.

Just install the PURGE solenoid and have your PCM reprogrammed "correctly" for your swap and you'll be fine.

-ryan

[This message has been edited by Darth Fiero (edited 05-09-2011).]

quote Originally posted by Darth Fiero: The purge solenoid valve is the only one you need to install. It will function as-needed once the PCM has been "properly" programmed for a Fiero swap environment. -ryan

Knew it was only a matter of time before you responded

Know any good PCM programmers?

J/K
I WILL be contacting you once I get everything in order (whats staying and whats going) for my reprogram...

Another quick question about the canister vent valve and ty for explaining it purpose on the 3800.
If I do not need to use it w/ the stock fiero canister, how does air get in to "vent" the fumes? Is there some sort of one-way ck-valve that I am not seeing?

The fiero canister has three ports. The larger of the two comes from the fuel tank.
The other two are "T" together and lead to the evap vent solenoid then to the TB.

quote Originally posted by ALJR: Knew it was only a matter of time before you responded Know any good PCM programmers? J/K I WILL be contacting you once I get everything in order (whats staying and whats going) for my reprogram... Another quick question about the canister vent valve and ty for explaining it purpose on the 3800. If I do not need to use it w/ the stock fiero canister, how does air get in to "vent" the fumes? Is there some sort of one-way ck-valve that I am not seeing? The fiero canister has three ports. The larger of the two comes from the fuel tank. The other two are "T" together and lead to the evap vent solenoid then to the TB.

The stock Fiero gas cap has a one-way check valve that will allow air to get into the tank (so a significant amount of vacuum cannot build inside the tank) but will not allow pressure to get out.

The two lines coming off the charcoal canister that you "T" together get connected to the "CAN" port on the evap PURGE solenoid (not vent solenoid, you're not using the vent solenoid on the Fiero); then the remaining port on the evap PURGE solenoid gets connected to a manifold vacuum port (either the large port on the throttle body or one of the ports on that plastic vacuum "tree" that's on top of the supercharger).

quote Originally posted by Darth Fiero: The stock Fiero gas cap has a one-way check valve that will allow air to get into the tank (so a significant amount of vacuum cannot build inside the tank) but will not allow pressure to get out. The two lines coming off the charcoal canister that you "T" together get connected to the "CAN" port on the evap PURGE solenoid (not vent solenoid, you're not using the vent solenoid on the Fiero); then the remaining port on the evap PURGE solenoid gets connected to a manifold vacuum port (either the large port on the throttle body or one of the ports on that plastic vacuum "tree" that's on top of the supercharger).

Thank you sir!

just to be clear... of the three lines coming off the can, one goes to the tank per the diagram is left alone. the other two lines go to a vacuum port. so on my gen v, i have an available vacuum port on the vacuum distribution fitting on the top of the SC, i put a tee fitting on that and have the two evap lines going into that and somehow manage to get that vacuum to the fpr mounted by the fuel filter. and i getting this correct?

EDIT TO ADD: i have an 87 btw and can not fit the sc3 evap sol and retain use of the N* tb.

[This message has been edited by americasfuture2k (edited 05-12-2011).]

quote Originally posted by americasfuture2k: just to be clear... of the three lines coming off the can, one goes to the tank per the diagram is left alone. the other two lines go to a vacuum port.

The other two lines coming off the EVAP canister go to the "CAN" port on whatever EVAP purge solenoid you are using. Then the remaining port on the purge solenoid needs to get connected to a port on your engine that only sees vacuum.

quote so on my gen v, i have an available vacuum port on the vacuum distribution fitting on the top of the SC, i put a tee fitting on that and have the two evap lines going into that and somehow manage to get that vacuum to the fpr mounted by the fuel filter. and i getting this correct?

No. You left out the evap purge solenoid you'll need to use. Also, the fuel pressure regulator does NOT tap into the vacuum port on the top of the SC. The fuel pressure regulator needs to SHARE the vac/boost signal coming from the port that comes out of the lower intake manifold under the SC snout (faces passenger side of car) with the MAP sensor.

quote EDIT TO ADD: i have an 87 btw and can not fit the sc3 evap sol and retain use of the N* tb.

What AF2K is saying here is the OE 3800 Series 3 SC engine has the EVAP purge solenoid that mounts directly to the blower housing next to where the throttle body bolts on. But because he is running an adapter plate and different throttle body, the OE Series 3 EVAP purge solenoid can't be installed in that location. If it could, you could T together both vacuum lines coming from the charcoal canister and run them directly to this evap purge solenoid.

AF2K: Since you no longer have or can use the Series 3 EVAP purge solenoid, you'll need to get a EVAP purge solenoid from a Series 2 engine and install that between your charcoal canister and vacuum port on the top of the blower. Make sure you get the fuel pressure regulator's vac line hooked up to the port on the lower intake which it will be sharing with the MAP sensor. This is the only port on this engine that references both vacuum and boost. The port on top of the blower housing only references vacuum. The FPR (and MAP sensor) need to see boost also.

-ryan

I have been running the evap as Darth says for quite some time on a S2 NA install. I will try to get some pics of the vac lines when I get home. Intake manifold vacuum to a plastic Y adapter, to both ports on the charcoal can. Its that simple.

Here's how you should have it hooked up...

quote Originally posted by Darth Fiero: AF2K: Since you no longer have or can use the Series 3 EVAP purge solenoid, you'll need to get a EVAP purge solenoid from a Series 2 engine and install that between your charcoal canister and vacuum port on the top of the blower. Make sure you get the fuel pressure regulator's vac line hooked up to the port on the lower intake which it will be sharing with the MAP sensor. This is the only port on this engine that references both vacuum and boost. The port on top of the blower housing only references vacuum. The FPR (and MAP sensor) need to see boost also. -ryan

just looked it up on rock auto to know what to look for at the junkyard, definitely havent seen any newer l67's there. otherwise i would have grabbed a lot from them already. thru RA its only 19.88 for an AC Delco one. not bad. thanks for that bit of info ryan, i havent seen anyting that says that what is needed for making a SC3 run on a fiero using a SC2 PCM. hopefully this thread comes to use to those in the future doing this swap.

additionally: im surprised i never even saw anything mentioning this for any SC3 downgrading

excellent, thanks for the changed pic ryan. but might i make a suggestion for future searches, label that purge solenoid as the series 2 purge solenoid.

[This message has been edited by americasfuture2k (edited 05-13-2011).]

quote Originally posted by Darth Fiero: Here's how you should have it hooked up...

Another quick question
Why do we have to "T" together the two vacuum lines off the Fiero can? Do the two lines go to two seperate sections in the can? Or is one line to open a valve and the other to vent the gas?

quote Originally posted by ALJR: Another quick question Why do we have to "T" together the two vacuum lines off the Fiero can? Do the two lines go to two seperate sections in the can? Or is one line to open a valve and the other to vent the gas?

Yes, the vacuum port on the very top of the canister controls the valve on the canister. The other port below it is the vapor purge line. Vacuum must be applied to the valve to allow the purge. Using the vacuum T or Y will permit this.

quote Originally posted by Darth Fiero: Yes, the vacuum port on the very top of the canister controls the valve on the canister. The other port below it is the vapor purge line. Vacuum must be applied to the valve to allow the purge. Using the vacuum T or Y will permit this.

Is the vlave on the conister nessasary when using the 3800 evap solenoid? Meaning if the canister valve was always open, would it matter. I am asking because I am wondering if I can modify the can valve to always be open so I would not need to use a "T"... Just a thought...

quote Originally posted by ALJR: Is the vlave on the conister nessasary when using the 3800 evap solenoid? Meaning if the canister valve was always open, would it matter. I am asking because I am wondering if I can modify the can valve to always be open so I would not need to use a "T"... Just a thought...

The design of the Fiero's charcoal canister requires the valve to be in place. Good luck getting it off of there without damaging either the canister or the valve, or ending up with a vacuum leak after you are done "modifying" the valve so it is always open. I think an assortment of vacuum T's at the auto parts store is $1.29 or something... Seems like a small price to pay vs. the risk of damaging your stock canister and then having to find a replacement.

quote Originally posted by Darth Fiero: The design of the Fiero's charcoal canister requires the valve to be in place. Good luck getting it off of there without damaging either the canister or the valve, or ending up with a vacuum leak after you are done "modifying" the valve so it is always open. I think an assortment of vacuum T's at the auto parts store is $1.29 or something... Seems like a small price to pay vs. the risk of damaging your stock canister and then having to find a replacement.

Thanks,I agree... Just curious, thats all