Other issues related to purge control solenoid valve Code 35

[ttt]

Hello everyone, I have a 1992 Legacy. Recently the CEL came on. The code I get when I connect the green diagnostic cables under the steering wheel is 35, indicating a problem with the purge control solenoid valve.

Otherwise, and I'm a novice so I won't try pretending like I know what I'm doing, but I have also noticed that when I unscrew the gas cap, there is quite a bit of suction coming from the tank side. Furthermore I recently noticed my exhaust has a rich smell. I got the car only several months ago, and I can't say when the suction/rich smell started. They may have started the same time as the CEL, but I'm not sure.

Does anyone know if these are problems diagnostic of anything related to the purge control solenoid? Is the gas tank supposed to be at lower pressure than the atmosphere?

More generally, I would like to learn to start systematically troubleshooting problems like this. I could probably figure out how to replace the valve, but I would like to know other things I should check first in case that isn't the problem. What manual(s) would you recommend I acquire in order to see other things I should do? It would be nice if I didn't have to research every possible problem every time something like this comes up, but had a guide that helped me eliminate problems efficiently.

Anyway, thanks for any help or advice!

[Legacy777]

From your post I would be 99% confident to say that your problem is the purge control solenoid or less likely the wiring for the purge solenoid.

 

The hissing you're hearing from the gas tank is pressure, not vacuum. Gasoline will produce vapors and create pressure. The charcoal canister in the front of the car is supposed to draw these vapors in, and the canister purge solenoid opens at certain times to pull those vapors into the engine to be burned. When the canister purge solenoid does not work the vapors can build up in the charcoal canister and tank, which will increase the pressure and you'll hear the hissing noise for an extended amount of time.

 

I would recommend replacing the canister purge solenoid valve.

[ttt]

Thanks for giving me a moment of clarity. I just opened my gas cap and used placed my hand along the side to tell if the tank was sucking in or blowing. I had assume there was suction for some reason, but just now I observed, as you said, that it was blowing.

So you think I should just order the part and not worry about diagnosing the wiring? Just as a point of interest, do you know an easy way I could test if the valve is working? I assume there's a way I could see if it opens or closes when power is supplied.

Thanks!

[Legacy777]

You can't see if the valve is working, but you can hear if it's working. If it's opening/closing it will make a clicking noise. You can apply 12v to one of the pins and ground to the other pin and the relay should click. Also, you can measure the resistance across the pins of the valve. It should be near 36 ohms.

 

Alternatively, you can plug in the green diagnostic connectors, put the ignition in the ON position, and the ECU will cycle on and off all of the output devices, radiator fans, canister purge solenoid, etc. With the canister purge solenoid electrical connector removed you can put a voltmeter on the pins and check for 12v cycling on and off. If you see 12v cycling on and off, the wiring and the ECU are good, and it's definitely the solenoid.