wxman94ej1

Thanks! Pleasure was all mine, really enjoyed meeting up and looking forward to wrenching a bit if it works out in the future. Nice to meet someone from H/T "IRL"

94 Civic Si

Agreed! It would be fun to turn some wrenches, and you have given me some suspension ideas.

Hopefully you can tell me about the 2-way valve replacement on your fuel tank soon...

94 Civic Si

Stashing a couple of ideas here for when I tackle the moon roof...

1) add a factory DC2 map light! https://honda-tech.com/forums/honda-...-roof-2595546/

2) Super Lube grease:

94 Civic Si

Just an update on evap system - it is getting warmer here (close to 80 today) and I went out to run errands at lunch w/ about 1/2 full tank of fuel. After a few heat cycles, I could smell the charcoal can when I would stop at a light. It went away when driving, so I started putting the blower on Recirc when pulling up to lights. Best of all is that the car does not stumble off idle when pulling away from lights.
Not sure if the can is just old, and that is why it smells when hot?
I am going to try one of the cans from @wxman94ej1 and see how that works.

wxman94ej1

Hmm. Curious to see if the other cans offer any difference.

I replied in another thread showing the two-way valve on the gas tank. I still haven't found 10 minutes to go out and blow in my new one and figure the thing out. I will definitely let you know when I do though!

I had some trouble the other day, but haven't had a chance to investigate. Major problems starting when hot. Seems like possible main relay issue, but need to investigate more. Good news is I have a decent line on a used A/C setup so hopefully picking that up soon. Probably won't do the project for awhile but I'll at least have the parts!

Glad to hear the EH3 is running good aside from fuel smell!

94 Civic Si

Me too! I have heard of folks cutting open cans from different vehicles and refreshing the charcoal media...

I had problems with no start when hot and ended up replacing the main relay. I do not remember if I kept my old one? If I did, you are welcome to it to see if it just needs to be re-soldered,

Can't wait to hear more about the A/C setup!

94eg!

iTrader: (2)

It's not the charcoal inside that is the problem. It's the shear volume of fumes when you add engine bay heat of the AC system. Both my CRX and Civic do this when running the AC. Changing charcoal canisters did nothing.

This is the exact reason OBD2 systems use a sealed canister, and large solenoid operated vacuum line. The system is easily purged in moments. The pre-obd2 EVAP system sucks by comparison.

OH BTW: If you relieve your fuel tank pressure just before you go for your drive (loosen & tighten gas cap) you will greatly increase the amount of time it takes for the EVAP system to become overloaded. I was doing this last summer when I had a 40 minute drive home in 110+ heat.

94 Civic Si

Thank you for that! I do have the larger, OBD2 style solenoid on the '96 B18. I think one of the charcoal cans that @wxman94ej1 gave me is the smaller can size, so it will fit my firewall, but has the 2 ports, vs. my older, OBD1, 3 port style can. I will check it out...

Thanks again for your experience.

94eg!

iTrader: (2)

You have an OBD2 motor and an OBD1 chassis?

wxman94ej1

Really glad to see you chime in here 94eg!. I've used your previous threads as a guide for my investigation about these darn canisters and it's been helpful, so thanks!

Yes, from my understanding he's running a 96 spec B18C (OBD2) in a 94 EH3 chassis (OBD1), with a P72 (OBD2) ECU. But he can confirm for sure...

94 Civic Si

Correct! Body is '94, and engine is '96.

You can witness my ramblings about this here:

https://honda-tech.com/forums/honda-.../#post51094702

and

https://honda-tech.com/forums/honda-.../#post51107787

94 Civic Si

Very close - OBD1 P72 ECU so I could plug in body wiring harness using the OBD1 connectors...

94eg!

iTrader: (2)

Okay so you pretty much have the same setup as me...
- 94 Civic CX
- 97 B18C R swap
- OBD1 chipped P05

So 1st, know your JDM 96-97 DC2 had a nearly identical EVAP system to your 94 Civic. Both have a 3 port Charcoal canister with a vacuum operated diaphragm valve. Both vent the canister to nipple on the throttle body. Both receive the vacuum signal from a small nipple on the intake manifold. The only difference between the two, is that the US model has an ECU operated solenoid that controls the vacuum signal to the charcoal canister. This means venting into the throttle body only happens at the demand of the ECU (instead of whenever the engine is on for the JDM ITR).

Your US spec ECU wants to see that EVAP Purge-Solenoid, so grab it off the intake-manifold of your old motor. Run a line from the nipple on the back of the ITR manifold down to the Purge Solenoid (I zip tied my solenoid the harness under the manifold), then run the output of the purge-solenoid to the top nipple on your original charcoal canister. Now you have the exact EVAP setup your original motor had AND your ECU wants to see.

This OBD1 EVAP system works fine in most circumstances, but can/will be overwhelmed in the summer heat with AC running. The fuel tank creates fumes faster than the Throttle Body sucks them in. There is really nothing you can do about it. Converting to an OBD2 "sealed" EVAP system (which your over-sized solenoid is part of) may be extremely complicated and would require you to replace your intake manifold, throttle body, and even ECU with the US-Spec B18C5 versions for proper operation. This means no chipping/tuning.

wxman94ej1

I am going to just apologize for interjecting myself here and let you guys hash this out, because I mis-spoke and led 94eg! to believe that you had a JDM motor, when in fact I think it's a B18C1 (USDM, forgot the "1" in my original reply). So anyway, I will see myself out now and follow along. Sorry for the confusion!

94eg!

iTrader: (2)

Uh, okay... it's kinda coming together now. This guys threads are very long and unfortunately I have no time to read them.

I can say this.... you NEED to match your EVAP system to your ECU since the specific solenoid is operated by the ECU (including fuel/timing compensations & purge duration). If the engine isn't recieving whatever the ECU programmed to expect, you will end up with weird idle problems. Therefore if you have an OBD1 ECU, run an OBD1 EVAP system. The problem you will have is adapting that system to an OBD2-US-spec motor (if that's indeed what you have). The ports are all wrong.

If that is the case, your simplest option would be to swap your Intake manifold & throttle body for the JDM-spec versions. Then hook up your original EVAP system. The much more complicated option would be to convert to the US-spec 96 ITR ECU & EVAP system.

94 Civic Si

Thanks @94eg!

For purposes of clarity, I am running the following:
-'94 Civic Si
-'96 B18C1 from GSR
-OBD1 P72 ECU
-Charcoal canister native to my '94 Civic body
-Evap purge solenoid native to my '96 B18C1

As for when the ECU commands the evap purge solenoid to open and purge the can, it does not look very elaborate - more details on that below.

No worries! I should have read a little closer and clarified I am running a US-spec B18C1 from GSR. Thanks for your help.

Sorry for the confusion! Thank you for your help. I do strive to write detailed threads that might help some curious searcher in the future. At the time I was writing, I was trying to figure out what the shop that did my swap came up with, as they were poor communicators.

I know all about what you mean about matching ports between OBD1 charcoal can and OBD2 purge solenoid. I got lucky when the swap shop put a throttle body on with a purge connection, and now I have married the two, and no longer have the weird idle problems that you refer to, and I experienced. As you stated earlier, that small port just cannot purge the can fast enough to keep the vapors from coming out the bottom when it is hot out and AC is on.

My OBD1 P72 ECU seems happy with the OBD2 purge solenoid on my B18C1, no CEL. There seems to be very little difference between how the ECU controls the evap purge solenoid in '94 vs. '96, even though the plumbing is very different. In '94, once the engine coolant temp hit 163 F, it opened the solenoid, which directed vacuum to the diaphragm, allowing the throttle body vacuum nipple to purge the can. There is not supposed to be any vacuum to that port at idle. In '96, once the engine coolant temp hit 154 F, it opened the purge solenoid and I believe this directed a continuous vacuum from the intake to the can - no diaphragm or TB involved. See images from the '94 and '96 Integra manuals below. I think the reference to "AND AC is on" is a typo and should read "OR AC is on" I do not see anything in the manuals about controlling duration of the purge, or compensating for anything, etc.

These systems aren't that complex, but they sure can make life miserable when they are not correct! Weird idle, bad smells, etc. It is too bad that most people's answer is to "yank all that smog crap out" when you search.

@wxman94ej1 was kind enough to give me some cans that he collected. I believe one of them is the smaller can to fit my firewall, but with OBD2 ports (larger, no diaphragm). If yes then I will try to swap that one in and plumb directly to the purge solenoid, and cap off the vacuum nipple on my TB and see how that performs in terms of idle and air/vapor quality.

94eg!

iTrader: (2)

It makes perfect sense that your system is functioning normal. The OBD1 ECU is operating the larger purge solenoid in the same manner it would a small signal purge solenoid. It doesn't actually flow the fumes through the solenoid as true OBD2 EVAP system does.

I have a feeling you will run into trouble if you attempt to plumb an OBD2 canister through the solenoid directly to the manifold.

94 Civic Si

I suspect you might be right - this may be "as good as it gets".

It is interesting that Honda/Acura used 3 different configurations of evap systems between looking at the '94 Integra FSM vs. the '96 vs. the '98. It isn't as easy as it looks to get these things to function properly.

Thank you for weighing in on my build. I will have to go and find your build, it sounds interesting...

94 Civic Si

I see your earlier thoughts on the topic here: https://honda-tech.com/forums/acura-integra-type-r-8/anyone-jdm-type-r-jdm-shop-manual-please-help-3206838/

https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/evap-charcoal-canister-fumes-smell-gas-fuel-3150846/#post49755715

Question - what do you mean by "sealed" canister when referring to the OBD2 can? It still has the fresh air tube from the bottom, eh?

94eg!

iTrader: (2)

Now that I researched it a little more, it appears the 98+ is the one with the completely sealed system. By sealed, I mean that the fresh air vent (that is opened on the OBD1) is now plugged by an additional solenoid controlled by the ECU. I'm a little lost on how the 96-97 system works. From the evap diagram it looks like it may still have an open vent on the bottom (kinda a hybrid of the two). I wish I had the book to help understand it better.

You may want to go ahead and attempt to hook up a 96-97 integra EVAP canister (the one with the 3rd port capped). It would be interesting to see if the OBD1 ECU operates the system in the same manner.

94 Civic Si

That makes more sense. I see that things did get pretty elaborate in '98+ with the control on the bottom of the can. Glad I don't have to deal with that!

I think the biggest difference is they are not purging the can through a little port on the TB. The lines were bigger (8mm?). But perhaps it was not all that great if they only kept it for 2 years? Or perhaps the EPA forced this...

I did want to know how the '96 system works, so I threw down the $ for a '96 Integra FSM. I detailed what I learned in one of my "long" posts below. If you want to know anything else, let me know!

Here are a bunch of pics from the '96 FSM as to how the evap system was designed:

94eg!

iTrader: (2)

For some reason I cannot see your pics.

To me it sounds like the 96-97 system could potentially be better than the OBD1 one. From the look of the 96-97 canister, it's been modified (from OBD1) to actually flow fumes through the diaphragm valve using actual manifold vacuum. This should be more efficient at evacuation than the crappy OBD1 port on the throttle body (which is NOT a good source of vacuum). Personally I would try the 96 canister hooked up just like your 96 manual shows and see if the OBD1 ECU operates everything properly without causing idle issues.

Then let us know if it helps with the problem of fumes when it's hot & running AC. lol

96-97 canister (round can, larger top port, capped lower port, large open bottom fresh-air port)

94eg!

iTrader: (2)

For reference 98+ spec canister with vent-shut valve on top that controls the systems access to fresh air (unlike the "open" port on the bottom of earlier cans)

94 Civic Si

I can see your pics, I wonder why you cannot see mine? Hopefully someone else might chime in as to whether they can see them.

The can I got from @wxman94ej1 looks a little different than the OBD2 can you have pictured - there is no diaphragm at all. It looks a little bigger than the one that is in my '94, but I think it might fit.

I'll try to get pics, I am migrating all my crap to a new computer and it is a massive PITA.

wxman94ej1

FWIW, I can see the pictures when viewing on my computer. Maybe mobile is having a problem?