Engine Evap and charcoal cannister leak

ryan1994stang · Mar 14, 2026

Hi all.
Ive got a stock 94 GT that im having issues passing California emissions. It passes on everything, except for the evap pressure test. I replaced the vacuum lines going to the charcoal cannister and still failed. I purchased a smoke machine and realized the purge solenoid wasn't sealing completely, so I replaced. but after looking at the evap test instructions, it seems like they clamp the line before the solenoid, so that shouldn't have an effect on the pressure test. Only other place I can find smoke is on a line that runs through the fender well and opens to atmosphere, underneath the air intake. Ive found very little info on this line, as it doesn't really show up on any diagrams. Im assuming it comes from the charcoal cannister, but is it just a line to keep it from getting over pressurized? Wondering if this is normal, or should I just go ahead and replace the charcoal cannister as well? Thanks for any help.

PS: hard to get a good pic of the line, but it just clips to the frame and ends.

gkomo · Mar 14, 2026

Don’t quote me but I believe there should be something that the line in the fender goes to… I don’t think it just vents to atmosphere. I can’t think of the name of it off the top of my head but search for ‘mustang fender vacuum line’ or similar.

I’m also coming from foxbody knowledge so maybe the SN is in fact different.

Mustang5L5 · Mar 15, 2026

I haven't messed with an SN95 charcoal canister. There should be two lines connected to it. One from tank, and one from engine. The solenoid is from the line on the engine. The canister itself is open to atmosphere after the activated charcoal. Usually this is through the two caps on the top.

The way it works (again, coming from a fox) is that the tank is vented through the charcoal. SO as pressure builds it pushes air through the charcoal and out the caps. When pressure decreases, fresh air draws in through the caps and into the tank.

Under certain conditions, the solenoid opens and engine vacuum is used to pull fresh air through the caps, through the charcoal and into the engine. This prevents the charcoal from being over saturated.

Found a canister for sale on ebay, and it does look like there are three lines. The caps that would be on the fox car appear to be replaced with connections for a line but since the canister itself is the same for 79-95, i assume that line is pulling fresh air from some other location??

1994-1995 Ford Mustang Charcoal Canister Smog Box Exhaust Emissions & Bracket | Genuine OEM | Direct Replacement

A used OEM PART WORKS PERFECT REMOVED FROM A 94 COBRA MUSTANG // I ONLY KEEP NICE ONES // This is in good used condition. This is a photo OF ACTUAL PART YOU WILL RECEIVE.

www.ebay.com

EDIT: did find this diagram listed for a 1994 Mustang

nickyb · Mar 15, 2026

With all the electric vehicles in Commifornia you think they can leave the 30 + year old cars a break.

gkomo · Mar 15, 2026

I think I was thinking of this red circled part:

ryan1994stang · Mar 15, 2026

Thank you all for the input. I pulled out the fender well today, and it seems very similar to the diagram mustang5l5 posted. Just instead of the dust caps, it has a line running from those 2 ports and ends under the frame rail. Im assuming to access a little more fresh air.
I ended up plugging that line, then using the smoke machine to pressurize the evap system from the fuel neck. I turned it off, waited about 10 minutes and it was still under pressure when I disconnected the machine. So it seems like there are no leaks.
My only confusion now, is that they dont plug that line during the evap test, so it's never going to hold steady pressure.
Ive passed smog multiple times in the past, so im still kinda stumped how it's worked in the past, but not now.

2000xp8 · Mar 17, 2026

nickyb said:
With all the electric vehicles in Commifornia you think they can leave the 30 + year old cars a break.

I'm not against emissions, not to mention california has some places with really terrible air quality, so I get it. But what they should do is stop testing 95 and older non obdII cars that require extensive testing.
NJ stopped a long time ago, it doesn't make sense to test them. It costs too much, takes too much time and money for how few are actually on the roads. There is probably a good chance they use more energy testing them and create more pollution than the cars actually produce.
Nearly no one daily drives a car 1995 and older these days.

Mustang5L5 · Mar 18, 2026

2000xp8 said:
NJ stopped a long time ago, it doesn't make sense to test them. It costs too much, takes too much time and money for how few are actually on the roads.

MA stopped a long time ago too.

In fact it's a rolling 15 year cutoff. Anything older than that doesn't get any emissions test or OBD2 test. Same reasoning. Anything 15 years or older rusted out a long time ago, or is a seldom driven garage queen.

Mcmahst · Mar 18, 2026

They were doing that in Ca as well, but in I believe in 1992, they stopped the > 15 year old car exemption. So, 1975 and older became the permanent exempt vehicles. Efforts to resurrect this process over the year since have never had a strong enough following to push it through either house of the legislators in California.

Engine Evap and charcoal cannister leak

ryan1994stang

New Member

Attachments

gkomo

now i can hopefully expect to receive the shaft

Mustang5L5

That is…until I whipped out my Bissell

1994-1995 Ford Mustang Charcoal Canister Smog Box Exhaust Emissions & Bracket | Genuine OEM | Direct Replacement

nickyb

I gotta say i never painted my nuts, Never Ever

gkomo

now i can hopefully expect to receive the shaft

ryan1994stang

New Member

2000xp8

Mustang5L5

That is…until I whipped out my Bissell

Mcmahst

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Engine Evap and charcoal cannister leak

New Member

Attachments

now i can hopefully expect to receive the shaft

That is…until I whipped out my Bissell

I gotta say i never painted my nuts, Never Ever

now i can hopefully expect to receive the shaft

New Member

That is…until I whipped out my Bissell

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