Fox EVAP purge solenoid valve not working

PonyGTrider · Feb 5, 2021

Hi all I just ran into a problem, after driving for a while I stopped and started getting this strong raw fuel smell. went home and same strong smell I opened the hood and started checking things around finding no fuel leaks or anything like that. I then focused on the charcoal canister and noticed fumes coming around it and I thought well the venting solenoid valve got stuck closed. so I inspected it and it was opening but just a little bit so I decided to replace it. I used another valve used but plenty of flow when energized. took mi ride for a spin and the same thing happened. I recorded the fuel fumes coming out from the charcoal canister but couldn't attach the file. I checked the wiring harness and there is 12 Volt power on the red wire but the ground wire which is the one the ECU controls never showed up, and that's why the valve never opens to let the fumes going to the intake manifold and they escape thru the upper breathing holes on top of the canister, and even the fuel pump sounds louder when opening the switch I guess because the fuel tank is under certain pressure as the purge solenoid valve won't open to release that pressure into the intake manifold (My theory anyways) checked the wire at the connector next to the ECT sensor and ZERO ground. so what to do? The purge valve is good and I got 12 volts to it but no ground.... I believe that ground comes from pin 31 at the ECU. I haven't checked ground at the pin but assuming I got NO ground signal out of pin No 31 what to do next?
Should I see ground signal as I open the switch? At cruising speeds? Or when should the ground show up???

Thank you all for the help

Mustang5L5 · Feb 5, 2021

It’s pin 31 on the ECU. You’ll want to test the wire from the purge valve connector back to the ECU and verify continuity on the entire wire.

how are you testing pin 31 for functionality?

also, you are visually seeing fumes from the canister? How much fumes?

PonyGTrider · Feb 5, 2021

Mustang5L5 said:
It’s pin 31 on the ECU. You’ll want to test the wire from the purge valve connector back to the ECU and verify continuity on the entire wire.

how are you testing pin 31 for functionality?

also, you are visually seeing fumes from the canister? How much fumes?

Thank you for the reply,
Yes I will undo the ECU connector to check that wire continuity. What about if pin number 31 is dead? how to proceed from there? I have a spare ECU which I may try if the wire from the solenoid to the computer harness is fine and pin 31 is dead.
Fumes? Oh a see lots of fumes on top of the charcoal canister and that's what scares the hell out of me, a spark and it will be nasty :O

Trying to attach a video but it is an mp4 and don't let me....

Thanks man

Mustang5L5 · Feb 5, 2021

I’ve never seen a pin 31 failure. If that’s that case I’d have to investigate the board. I would do my best to investigate the wiring in the car first.

have you dumped the codes. An eVap issue would register as a code 85.

but we will need to talk about those fumes as well....

PonyGTrider · Feb 5, 2021

Mustang5L5 said:
I’ve never seen a pin 31 failure. If that’s that case I’d have to investigate the board. I would do my best to investigate the wiring in the car first.

have you dumped the codes. An eVap issue would register as a code 85.

but we will need to talk about those fumes as well....

Yes I scanned the system end got code 85 but that code got registered when I unplugged the wiring harness from the EVAP purge control valve and the vacuum hoses from the purge valve causing a lean condition.
As far as I know code 85 will be triggered when the EVAP purge solenoid valve fails and stays stuck open, unmetered air and fuel fumes enter the intake manifold causing the engine to stumble and hard to idle...... I think

Thank you, I'll try all your troubleshooting suggestions.

PonyGTrider · Feb 6, 2021

PonyGTrider said:
Yes I scanned the system end got code 85 but that code got registered when I unplugged the wiring harness from the EVAP purge control valve and the vacuum hoses from the purge valve causing a lean condition.
As far as I know code 85 will be triggered when the EVAP purge solenoid valve fails and stays stuck open, unmetered air and fuel fumes enter the intake manifold causing the engine to stumble and hard to idle...... I think

Thank you, I'll try all your troubleshooting suggestions.

UPDATE: Ok I tested the EVAP purge solenoid valve ground wire from the connector next to the ECT sensor to the ECU harness at pin 31 and there is no interruption on continuity, the wire is good. There is another extension from the connector next to the ECT sensor and I'm a bit suspicious of potential false contact there, so I will cut the connector and splice the two wires going to the EVAP purge solenoid valve to eliminate that possibility.

So if splicing those two wires don't solve the issue that means pin 31 is dead . So does anyone have any suggestions on how to repair the ground signal on pin 31 (If that was the case)?
Like I mentioned before I have a spare ECU I bought long time ago at Autozone and could use it, but I have no idea what model it is, no labels no nothing! so I would like to fix my A9L if pin 31 is bad. or is there a way to identify the spare ECU unit by the internal components? maybe I have two A9L's.

Any help will be appreciated

PonyGTrider · Feb 6, 2021

PonyGTrider said:
UPDATE: Ok I tested the EVAP purge solenoid valve ground wire from the connector next to the ECT sensor to the ECU harness at pin 31 and there is no interruption on continuity, the wire is good. There is another extension from the connector next to the ECT sensor and I'm a bit suspicious of potential false contact there, so I will cut the connector and splice the two wires going to the EVAP purge solenoid valve to eliminate that possibility.

So if splicing those two wires don't solve the issue that means pin 31 is dead . So does anyone have any suggestions on how to repair the ground signal on pin 31 (If that was the case)?
Like I mentioned before I have a spare ECU I bought long time ago at Autozone and could use it, but I have no idea what model it is, no labels no nothing! so I would like to fix my A9L if pin 31 is bad. or is there a way to identify the spare ECU unit by the internal components? maybe I have two A9L's.

Any help will be appreciated

Well guys, great news!!! Problem solved the fumes are gone. The problem was a stupid connector next to the ECT sensor I cut off both connectors and soldered the two wires going to the EVAP purge solenoid valve and now it is working properly. I still see a very light hinto of vapors on top the charcoal canister but I assume it is almost normal for a thirty years old piece.. Case closed and hope this posting light up some solving ideas to others experiencing the same issue.

Thank you all

Mustang5L5 · Feb 6, 2021

Vapors coming from the canister is still not normal. Under certain conditions those can ignite. Are you actually seeing smoke? Or are you seeing the haze of gas vapors?

you may need to replace the canister if it’s over saturated, but the level of fumes would have mr concerned. Guys have deleted the canister completely and can only smell the fumes on a hot day.

7991LXnSHO · Feb 6, 2021

About the ECU, if it is not labeled I do not know how to ID it. If the now used A9l gets senile, The ECU exchange can fix it fast, well and not at a bad cost. The can probably ID and test the other one.

pavlos413 · Jul 26, 2021

PonyGTrider said:
UPDATE: Ok I tested the EVAP purge solenoid valve ground wire from the connector next to the ECT sensor to the ECU harness at pin 31 and there is no interruption on continuity, the wire is good. There is another extension from the connector next to the ECT sensor and I'm a bit suspicious of potential false contact there, so I will cut the connector and splice the two wires going to the EVAP purge solenoid valve to eliminate that possibility.

So if splicing those two wires don't solve the issue that means pin 31 is dead . So does anyone have any suggestions on how to repair the ground signal on pin 31 (If that was the case)?
Like I mentioned before I have a spare ECU I bought long time ago at Autozone and could use it, but I have no idea what model it is, no labels no nothing! so I would like to fix my A9L if pin 31 is bad. or is there a way to identify the spare ECU unit by the internal components? maybe I have two A9L's.

Any help will be appreciated

Thank you for sharing this information...I was having I believe the same problem lately...after driving for a while during hot summer days my car would reek of raw gasoline in the garage. I was changing all the fuel rubber lines and even had bought a new charcoal canister and purge valve...well when the smell kept coming from the canister area, I checked my gas cap to see if the tank was full of pressure and it hissed out air for a long time...I believe the purge valve wasn't opening to allow the fume into the manifold like it's supposed to...I chopped off the old connector, and spliced the lines directly to the connector on the purge valve...I hope this works. I will let you know soon if it worked. But as far as I know, there can be no other reason for the gas fumes constantly coming from the canister unless the valve isn't opening.

PonyGTrider said:
Well guys, great news!!! Problem solved the fumes are gone. The problem was a stupid connector next to the ECT sensor I cut off both connectors and soldered the two wires going to the EVAP purge solenoid valve and now it is working properly. I still see a very light hinto of vapors on top the charcoal canister but I assume it is almost normal for a thirty years old piece.. Case closed and hope this posting light up some solving ideas to others experiencing the same issue.

Thank you all

PonyGTrider · Mar 19, 2026

Hi all
Here I’m reviving this post because my raw gas fumes were gone for a while, well today those fumes came back and not sure what’s going on.
A quick synopsis about this issue is that after having that raw gas smell I opened the charcoal canister and dried the fuel soaked carbon pellets with heat until they were dried with no more gas smell so I sealed the canister and was good after that up until now.
I ran a scan for possible error codes and there was only one code but it is not related to this issue Code 34.

I took a short video and you can see the gas fumes harboring around the charcoal canister.
Sorry I couldn’t upload the video
So what now?
Get a new canister? But why those pellets got soaked again that rapidly? I never top the fuel tank so there is no actual fluid traveling to the charcoal canister only vapor.
Please give me your opinions… Thank you

AeroCoupe · Mar 19, 2026

I would say that somehow or another the solenoid is not opening long enough or often enough to allow the engine vacuum to draw across the charcoal and dry it out. Could even be that the solenoid valve is not opening or opening all the way, partially obstructed line from the tank to the canister or the canister itself just needs to be replaced.

PonyGTrider · Mar 19, 2026

AeroCoupe said:
I would say that somehow or another the solenoid is not opening long enough or often enough to allow the engine vacuum to draw across the charcoal and dry it out. Could even be that the solenoid valve is not opening or opening all the way, partially obstructed line from the tank to the canister or the canister itself just needs to be replaced.

Even though there were no error codes coming from the purge valve I will physically verify if it is opening/closing properly.

PonyGTrider · Mar 19, 2026

PonyGTrider said:
Even though there were no error codes coming from the purge valve I will physically verify if it is opening/closing properly.

I just checked the EVAP purge valve and it is functioning correctly, and just for pace of mind I cleaned it with throttle body cleaner but it opens and closes fine and again no error codes.

Mustang5L5 · Mar 19, 2026

So the function of the purge valve is to open and allow engine vacuum to draw fresh air through the two caps on the top, through the charcoal and into the engine. This purges the charcoal of excess vapor.

When the purge valve is closed, the gas tank is vented to atmosphere through those caps. So as tank pressure builds, it vents through the charcoal and out the caps. As tank pressure relieves, it pulls air through the caps, through the charcoal and into the tank.

Have you smoked tested both sides of the canister to see if there are any leaks anywhere that count contribute to the fumes?

Also are you noticing any sort of trend with regards to when you smell the fumes?

My solenoid is non functional but I left everything hooked up. I don’t get any noticable fumes, even with my 39 year old canister still in place. So I wonder what else would cause the fumes to be obvious?

PonyGTrider · Mar 19, 2026

Mustang5L5 said:
So the function of the purge valve is to open and allow engine vacuum to draw fresh air through the two caps on the top, through the charcoal and into the engine. This purges the charcoal of excess vapor.

When the purge valve is closed, the gas tank is vented to atmosphere through those caps. So as tank pressure builds, it vents through the charcoal and out the caps. As tank pressure relieves, it pulls air through the caps, through the charcoal and into the tank.

Have you smoked tested both sides of the canister to see if there are any leaks anywhere that count contribute to the fumes?

Also are you noticing any sort of trend with regards to when you smell the fumes?

My solenoid is non functional but I left everything hooked up. I don’t get any noticable fumes, even with my 39 year old canister still in place. So I wonder what else would cause the fumes to be obvious?

No I haven’t run any smoke test,
Funny thing is that after I removed the purge valve for testing and had it flushed with TB cleaner I I went for a ride and no noticeable raw gas smell, so probably the solenoid was a bit sticky and not opening by the computer command.
I will keep monitoring it closely.
One thing doesn’t make much sense when you say that your solenoid is non functional and you don’t get fumes, in other words you are not evacuating the fumes stored in the canister so where those fumes go? They have to go somewhere so there has to be raw gas smell… so maybe I don’t understand how the system works.

Mustang5L5 · Mar 20, 2026

PonyGTrider said:
One thing doesn’t make much sense when you say that your solenoid is non functional and you don’t get fumes, in other words you are not evacuating the fumes stored in the canister so where those fumes go? They have to go somewhere so there has to be raw gas smell… so maybe I don’t understand how the system works.

I fully intend to start getting the smell at some point. The activated charcoal can only absorb so much. In which case i'll have to regen ( remove and hook a vac pump to and vent for hours) or replace.

The system is essentially a vent through the charcoal. It's not 100% sealed. The charcoal acts as a filter, and the function of the purge solenoid is to open the system to vac to pull clean air through and "flush" the charcoal. At some point it will oversaturate and you will get fumes (assuming no leak)

Not an accurate diagram, but the "clean air" vent is equal to the two caps on the top of the canister. "purge pipeline" is the line running to the solenoid. That opens and pulls clean air through the charcoal and into the engine. When it closes, the gas tank pressure forces flow from the orange "fuel tank" line through the charcoal and the excess vents out the blue "clean air".

SO hopefully the above explanation kinda helps you troubleshoot this.

Here's some "out there" questions to maybe think about some other things. Do you fill your tank to the top? DO you notice this smell after a full tank of gas? Do you ever see raw gas in the line? If you remove your gas cap when you smell this, go you get a hiss, or nothing at all? Any changes in the tank plumbing?

Mcmahst · Mar 20, 2026

Just for grins, have you done anything to the stock fuel tank, fuel pump or lines? I ask because I wonder if the vent line is ingesting raw fuel into it. Just a thought. Good luck.

AeroCoupe · Mar 20, 2026

I will say that when I dropped my tank this last time to work the fuel system over I did install a new filler neck seal, new vent line check valve & seal, and new o-rings/seals on the fuel pump hanger and sending unit. I have zero gas smell in the garage. The charcoal canister is original to the car.

PonyGTrider · Mar 20, 2026

The

AeroCoupe said:
I will say that when I dropped my tank this last time to work the fuel system over I did install a new filler neck seal, new vent line check valve & seal, and new o-rings/seals on the fuel pump hanger and sending unit. I have zero gas smell in the garage. The charcoal canister is original to the car.

Good ideas, one ring I haven’t check if the system is sucking raw fuel instead of fumes only, I’ll do as soon as I have some free time.

Thank you

Fox EVAP purge solenoid valve not working

PonyGTrider

Mustang5L5

That is…until I whipped out my Bissell

PonyGTrider

Mustang5L5

That is…until I whipped out my Bissell

PonyGTrider

PonyGTrider

PonyGTrider

Mustang5L5

That is…until I whipped out my Bissell

7991LXnSHO

wanna catch the space herp

pavlos413

Member

PonyGTrider

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

PonyGTrider

Mustang5L5

That is…until I whipped out my Bissell

PonyGTrider

Mustang5L5

That is…until I whipped out my Bissell

Mcmahst

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

Similar threads

Fox EVAP purge solenoid valve not working

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

wanna catch the space herp

Member

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

Similar threads

Privacy & Transparency

Privacy & Transparency