2008 SRT8 Challenger
So bill do you have any idea where this noisy bastard is on my 6.1 ? And is there any way to silence this thing without using a hammer. The noise drives me nuts and actually is embarrassing if you start it up in front of anyone.It took me a while to find the time to look for the CPS valve on my 2019 6.4L. Today was super nice outside so I took some photos and a video that I'll post on youtube, then I'll come back and update this with a link. The canister purge valve is part of the evaporative control system. It's a small 14V solenoid valve that allows the electronic throttle valve (ETC) to suck fuel vapor from the purge canister. Fuel vapor is collected by the purge canister while parked. The canister is a charcoal filled can that collects fuel vapor from the fuel tank.
In older cars, the purge valve was typically a linear solenoid meaning that it could be opened gradually. They didn't audibly click because the drive signal was typically 200Hz and the valve was controlled by varying the dutycycle of the signal. The valve moved softly so you would never hear it. If you could put your ear directly onto it, you would hear the 200Hz hum.
In newer cars, the linear solenoid has been replaced by the so-called digital CPS valve which is cheaper to manufacture and is a simple on/off valve. The linear valve had about 4 to 6 mm of travel and a tapered armature and seat. The further it opened, the more flow. The digital valve is only fully open or closed, no definable in-between. The average flow volume is determined by the overall dutycycle or on-time (open) with respect to off-time (closed). The typical operating frequency is around 16 Hz but the valve can work from 10Hz to about 40Hz. The digital CPS valve has a small hard rubber tip on its armature and it tends to harden in cold weather so when the car starts up cold, the CPS is louder than normal and that's when people are most likely to hear it.
Purge typically happens only for a few minutes after startup and then reduces greatly or stops. In other words, don't let the noise get to you. It doesn't go on forever.
If anyone is considering tampering with the CPS, I highly advise against that. Purge is critical to the EVAP system. Disconnecting the CPS valve electrical connector would leave the vehicle without any purge at all. Certainly, this will trip the check-engine light. By passing the valve would certainly flood the engine with purge flow and cause severe stalling and lugging that would never end. The reason the CPS valve operates at a reduced dutycycle and at a high frequency of movement is to provide a controlled average amount of flow. The ECU stops purging during acceleration and resumes when the engine is near idle or at a constant speed. Several sensors are monitoring this behavior... so do not mess with it or you'll be sorry.
I will provide a link to some photos and a video soon.
Just a note, for anyone who wonders, I have been an electronics engineer for the past 26 years working on evap product development for Siemens -> Siemens-VDO -> Continental -> Vitesco Technologies. This has been constant employment. Just the company name has changed several times over the years. My function has included creating many prototype level electronic drivers for linear and digital solenoids (including CPS, PPS linear or proportional purge solenoid, EGR exhaust gas recirculator, ETC electronic throttle valve, GPA general purpose actuator, and more). Speaking of GPA, there's one on the rear of the intake manifold on your 6.4L engine. It moves the runner valves inside the manifold. I helped design the GPA and the electronics within it. I also programmed it, both prototype and production level code. And no, I'm not allowed to share the source code. That's company IP. But I have to admit that I'm a little proud of the fact that there's a little of myself in every Challenger and Charger (and other Dodge vehicles, and GM, and others).