Context:
My Understanding:
My Questions:
- I'm troubleshooting MIL code 31 (P0441), which I posted about over here.
- This post led me to believe that my purge valve solenoid needed to be replaced, as mentioned here.
- Now I'm not so sure. Reasons given below.
My Understanding:
- The purge valve solenoid has two ports, each with a hose attached. One hose goes to a port on the intake manifold, and one hose goes to a port on the charcoal canister.
- The purge valve solenoid is "de-energized" until the TJ reaches operating temperature. During that time the TJ is in "open loop". At this time the purge-valve solenoid does not purge any vapors from the charcoal canister to the intake manifold.
- When the TJ reaches operating temperature, and is in "closed loop" operation, the purge valve solenoid will "pulse" anywhere from 5–10 times per second. This pulsing is what purges vapors from the charcoal canister and sends them to the intake manifold.
- Am I right so far?
My Questions:
- 1) Let's say I cold-start my TJ and immediately disconnect the purge-valve solenoid from the charcoal canister. One end of the hose is in my hand, and the other is still connected to the purge valve solenoid. I feel and hear a gentle, consistent suction in this hose. It's not very strong—in fact, if I reconnect that hose to the charcoal canister, and then remove the other hose from the other port on the charcoal canister, I cannot feel the same suction on that port. Is this gentle, constant suction normal while the TJ is in open loop operation? Is this just the vacuum pressure from the intake manifold, passing through the purge-valve solenoid?
- Answer: No, when the purge valve is closed (de-energized), no air should be passing through it. Especially if you unplug the purge valve's electrical connection, which would ensure that it is de-energized. In either case, you should not feel the intake manifold's vacuum pressure passing through the purge valve. See the first video posted here.
- 2) Let's say I let my TJ warm up to operating temperature, and now I disconnect the purge-valve solenoid from the charcoal canister. Again, one end of the hose is in my hand, and the other is still connected to the purge valve solenoid. What should I feel? How strong is this "pulsing" that it does? How long should I wait to feel it? When I try this, I only feel the same gentle, constant pressure that I feel described above.
- Answer: The vacuum pressure you should feel is just that same gentle pressure described above. However it should not be constant. You should feel and hear the purge valve pulsing, but that pulsing is just an opening and closing, so the pressure you feel during those pulses is no greater than the intake manifold vacuum pressure itself. See the second video posted here.
Last edited: