Charcoal canister missing a connection or maybe needing replacement

Conda

Conda

Daily Driver
Hey all, I've been chasing things creating an uneven idle on my 1987 FI X1/9 and one thing i noticed is that charcoal canister has a port on the top that is not connected to anything. With the charcoal canister connected to the intake, there is a noticeable vacuum at the 90 degree elbow on the top of the canister. I replaced the vacuum line going to the charcoal canister with a bolt that then sealed it up. Idle is now consistent but I realize that im probably venting all the fumes that should probably get burned by the engine (if possible).

The next time i fueled it up, i noticed a significant amount of pressure was released when i opened the gas cap, more than I am used to.

My questions are:
1. Should the 90 degree bend pointing to the front of the car be attached to anything or venting? (shop manual for FI seems to show nothing attached, but carb does.)
2. Should the same 90 degree bend have noticable vacuum if you put your thumb over the opening? (is this a symptom of a failed charcoal canister?)
3. Are there any valves on the vapor system? Will not having intake vacuum result in an over pressure situation in the gas tank?

Thanks everyone. I was going to post the image from the manual but i'm not sure if some copyright holder would shred me for it.
(edit: is/are)
 
That 90 should be open. I don't know about the vacuum. Let me go start my 86. :)

Update: Okay, my 86 is definitely pulling a vacuum on the opening of that 90 off the top of the canister. My theory is that the tank vents into the canister, then the engines sucks air backwards thru the canister in an effort to burn the gas fumes. Maybe?? :)
 
From the reading i have been doing lately on FI fiats, there is a metered cap on top of the canister. The orafice is a specific size. Also heard if it were missing it would cause it to be rich.

Odie
 
I put the hose from the intake to the charcoal canister back. Seems to run just fine. I did notice a decrease in my gas mileage with the previous tank with that port disconnected and plugged at the intake, I also did not notice a high pressure situation in the gas tank when opening it after a spirited drive. I think it's definitely best left connected. Thanks all.
 
Here's a snip from the parts manual:

vent.JPG


If you are referring to the vacuum hose highlighted in light blue, then Yes this should be in-place. It's a very small diameter hose that applies manifold vacuum to the charcoal canister to help purge the fumes absorbed by the charcoal and suck the fumes into the engine to be burned. If the small hose is disconnected at either end, you are going to have a manifold vacuum leak causing idle issues and lean running.

Note the very large diameter 90 degree port on top of the canister, with a hose that leads to a T on the FI snorkel. All of the hose parts have (1980) next to them. One of our experience vendors should know if that means the hose is only used on all 1980 models, only all California models, or only 1980 California models. All other years of federal FI should not have any hose from the large 90 degree elbow on the vapor canister going to the snorkel.

This is a guess, but I think the system was calibrated to allow for the amount of "false air" that is let into the induction system with this large elbow open to atmosphere. This is also a guess--however much that amount of false air was when the charcoal canister was when new, 33+ years later, that amount of "false air" is a LOT more than it was, and may be playing havoc with your idle smoothness and running smoothness.

Try an experiment, see if capping off the big 90 degree elbow makes things better or worse.
 
On my ‘79 carb’d version, that large elbow was connected to a fitting on the heat shield over the exhaust manifold. I assume to provide hot air to help purge the gas fumes in the canister. The small tube went to a port on the carb. My ‘81 had nothing attached to the large elbow.
 
So with the canister connected to the intake, ive noticed my idle is even but varies anywhere from 1100 to 1500. Not a huge deal, but i wonder if there is a more consistent vacuum canister i could possibly replace it with.
 
If your idle is varying that much there is a different issue. I would start at the intake plenum and move outward from there to find the false air (leaks). Unless your car has AC there isn’t an active system for idle control once the engine is warm so you either have an air leak or one of the components that do affect idle isn’t working properly.

I would start at the throttle plate, is it actually closed? Does the throttle plate reliably return to the closed position when you release the pedal? Is the vacuum port underneath clear? Is the throttle position sensor properly adjusted? And then move outward from there. The auxiliary air regulator is a strong candidate as the culprit but getting the baseline parts it relates to to a known nominal state is important.

This will likely require using the guide for the injection system to verify the coolant temperature sensor and the other parts of the system are actually working properly.

This is a nicely written and well regarded approach to working through the issues with L-Jetronic (it is on an Alfa but the base issues are the same).:

L-jetronic Fuel Injection Technical Troubleshooting Article

Technical Troubleshooting Article for L-Jetronic Fuel Injection.
www.hiperformancestore.com
 
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Conda said:
So with the canister connected to the intake, ive noticed my idle is even but varies anywhere from 1100 to 1500. Not a huge deal, but i wonder if there is a more consistent vacuum canister i could possibly replace it with.
Click to expand...

The large hose? That shouldn't be connected on the '87. Remove it. If you have an idle fluctuation, you will need to fault trace the air intake system in it's entirety, including spraying the plenum/runner gaskets to check for leakage. Also ignition/dist to make sure you don't have loose weights/advance mechanism issues.

EDIT - Karl got it covered...
 
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Back to the original post - there are two check valves in the evap system - both need to be functional or you will have a vacuum leak.

Dan's pic above doens't show the setup that would be on an '87 with the two check valves.
 
lookforjoe said:
Back to the original post - there are two check valves in the evap system - both need to be functional or you will have a vacuum leak.

Dan's pic above doens't show the setup that would be on an '87 with the two check valves.
Click to expand...

IIRC, the check valve that is unidentified in the top snip below is actually the green-circled check valve ID'd as 4388570 /448971 / 753246x in the bottom snip below.

vent.JPG


canister2.JPG
 
The lower schematic would be correct for 87 - in terms of actual location, one is close to the canister, the other is back by the frame rail where the side tray drain tube comes down

Mine is modified, however general placement is similar - rearward valve that attaches to lower cannister port (green circled valve above)
IMG-20191022-173123.jpg


foreward valve - set off the "y" to dump under the rail
IMG-20191021-184506.jpg
 
So I found that my auxiliary air valve was at least one source of a vacuum leak. For the time being I've replaced it with a brass manual valve that I had sitting around with some plumbing stuff, kinda nice to be able to set my "fast" idle speed manually and turn it down to a smooth 1000rpm when the engine gas warmed up a bit. I have not noticed any pressure issues in the tank since hooking up the line to the canister again, car seems to be running better overall. I will have a look inside the intake to make sure the throttle plate is closing all the way and that things are clean.

Thanks for all of the info.
 
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