Fox EVAP purge solenoid valve not working

PonyGTrider

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Feb 27, 2019
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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
 
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Mustang5L5

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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.

7A7AA203-D304-40F6-B6AB-3A7E1FA58BA7.jpeg


how are you testing pin 31 for functionality?

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

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Feb 27, 2019
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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.

7A7AA203-D304-40F6-B6AB-3A7E1FA58BA7.jpeg


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

i'm familiar with penetration
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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

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Feb 27, 2019
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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

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Feb 27, 2019
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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

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Feb 27, 2019
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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

i'm familiar with penetration
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Feb 18, 2001
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Massachusetts
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

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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.