[JohnWR]

Anyone know what the EVAP pressure should be once we are up to temperature and driving at highway speeds?

I am getting a P0455. I can see my live EVAP pressure at up 90 pascal. This equates to 0.68mmHg or 0.013 psi.

I am wondering if it is my Dorman Evap Purge Solenoid that I replaced. This code only appeared after I replaced my EVAP solenoid with a Dorman unit (I cracked my original one).

Any feedback is greatly appreciated.

The manual only states that the system has to show vacuum, with no other specified pressures. I am assuming that you are reporting gauge pressure and not absolute, and since that pressure is positive you are not seeing vacuum, hence the fault.

The diagnostic procedure starts with installing an independent vacuum gauge to compare readings and, if the readings disagree, to replace the sensor. If they agree, find the leak.

 

[JohnWR]

Anyone know what the EVAP pressure should be once we are up to temperature and driving at highway speeds?

I am getting a P0455. I can see my live EVAP pressure at up 90 pascal. This equates to 0.68mmHg or 0.013 psi.

I am wondering if it is my Dorman Evap Purge Solenoid that I replaced. This code only appeared after I replaced my EVAP solenoid with a Dorman unit (I cracked my original one).

Any feedback is greatly appreciated.

EvapP should always be negative while the engine is running.

I saw readings from -40 to -140 at idle.

 

[JohnWR]

Anyone know what the EVAP pressure should be once we are up to temperature and driving at highway speeds?

I am getting a P0455. I can see my live EVAP pressure at up 90 pascal. This equates to 0.68mmHg or 0.013 psi.

I am wondering if it is my Dorman Evap Purge Solenoid that I replaced. This code only appeared after I replaced my EVAP solenoid with a Dorman unit (I cracked my original one).

Any feedback is greatly appreciated.

Update after a few more drive cycles.

The first thing I think you should do is open the gas cap, start the engine, and read the EvapP. I would also check the EVAP valve open %. With the cap still open, shut off the engine and watch EvapP. Mine reads 0 Pa at that point, which is what I expect since that would equate to atmospheric pressure and the tank is mostly open to atmosphere.

While the EvapP is mainly negative, there were times during the second drive cycle that it went positive, and I suspect that is the vent valve closing and letting heat expand the fuel enough to build positive pressure. There is really nothing else that can generate positive pressure in the system with the engine at idle.

My suspicion is that your purge valve is not operating correctly, and is never getting vacuum to the system.

An open gas cap should not allow positive pressure to build, in fact I saw negative EvapP with the fuel cap off and the engine idling.

 

[JohnWR]

So I filled my tank to 3/4 this morning and monitored the Evap vapor pressure via my Torque app. It only peaked at 20 Pa. Yesterday at around a 1/4 tank it was up to 90 Pa.

When I got to work and let the vehicle idle, the Evap Vapor Pressure was still around 18-20 Pa. Leaving the car running, I got out of the vehicle and removed the gas cap. The EVAP Vapor Pressure never changed. It stayed the same regardless of whether the cap was on or off.

Now the values were changing (moving between 18-20 Pa and when I first started the car it was under 10 Pa), which I assume means the gauge is reading values.

So considering that the removal of the gas cap resulted in ZERO difference in Vapor Pressure, I assume the gas cap is the problem.

Did the pressure stay positive the whole time or was it mostly negative? Even with my gas cap off I was seeing negative pressure. The EvapP value only went to zero or slightly positive when the EVAP value showed zero % meaning that the valve was closed.

 

[JohnWR]

It was positive the entire time. I will see if I can take a pic of my Torque app live screen and share.

I am wondering if my app pulls the data and reports the 'absolute' pressure regardless of vacuum or not.

My Torque app delivers real time display of data. I have a page set up right now with EVAP and EvapP displaying as gauges. It is interesting to watch how it works.

Also, it shows positive and negative values.

 

[JohnWR]

This is at idle before it warmed up, with the gas cap removed. Notice that the valve is at zero percent open.

This is at idle after warm up, gas cap still removed. Notice that the valve is showing open partially.

I really believe it is your valve, or something related to it.

 

[JohnWR]

I am leaning toward my purge valve. From what I understand the vent solenoid (near the tank) closes and the purge valve is supposed to open to allow the engine to generate vacuum in the system at startup. Once vacuum is achieved, the PCM then signals the purge valve to close and monitors how long it takes to lose vacuum. The faster the system loses vacuum determines if it issues a large leak or small leak code.

I suspect my Dorman Purge solenoid is not opening at startup. As such, the system cannot generate vacuum. Hence the system issues a large leak fault due to its inability to even generate a vacuum.

I suppose a simple fix would be just to spend $50 and get the OEM purge solenoid and put it on to see. I will do that after I get back from vacation.

Outer Banks, NC here I come!!!

Have you watched the purge valve commanded position? Mine shows 0% open until the engine starts to warm up. The open-close routine happens multiple times and to different degrees, with a lot of time spent at low vacuum. It is quite an involved process.

 

[JohnWR]

My purge valve commanded position shows 'no data available'. On my torque pro app I only have 2 EVAP PID's to monitor. One is EVAP and the other is EVAP Pressure. The EVAP one states no data available.

I am going to monitor on my drive home from work to see if data begins to come available.

The system data shows EVAP System Test is 'incomplete'.

NA or GXP? I should have asked earlier. I have been testing with my RL.

 

[JohnWR]

2006 NA

I'll check mine this afternoon to see what I can access.

 

[JohnWR]

My purge valve commanded position shows 'no data available'. On my torque pro app I only have 2 EVAP PID's to monitor. One is EVAP and the other is EVAP Pressure. The EVAP one states no data available.

I am going to monitor on my drive home from work to see if data begins to come available.

The system data shows EVAP System Test is 'incomplete'.

My NA, as expected, does not have data for the Evap valve. I suspect the difference between NA and RL/GXP is due to the different ECMs.

Starting the engine and idling in the garage I saw -15 Pa with the gas cap removed and -25 Pa with it closed once it got to operating temperature. It only idled for about 5 minutes, so not long enough for the purge cycle to run. The book says it runs once within 17 minutes of starting if the ECT at start is below 86F.

Regardless, even with the gas cap off the system shows negative pressure, so we are back to the purge valve not opening.

 

[JohnWR]

Thanks for the update.

Very interesting results on my drive home last night. At start up the EVAP pressure was +15Pa. After about 1 minute (as I pulled out of my work), it dropped briefly to -40Pa (for about 3 seconds) and then jumped back up to hovering around -5Pa to +5Pa as I drove on the highway home (25 min drive).
Once I got off the highway, the pressure dropped to -15Pa and stayed there.

I checked again as I ran an errand and the pressure then was +15 to +20Pa for the entire trip.

So as you noted, I think it is my purge valve is not fully opening to draw vacuum. So either I have sticking valve gate or poor electrical connection in the purge valve. Considering this is the only item I changed and it never had an issue before, I assume the purge valve is the problem.

I will swap in an OEM one when I am back from vacation and update on any values I get with the new Purge Solenoid installed.

Note my gas cap is fairly new (less than 3 years old), as I left it on the trunk and pulled out of a gas station and lost my factory one

I didn't run the NA long enough for a purge cycle, but when it runs on the RL (and I assume it looks the same on both) the pressure drops to -1200 Pa for a brief time before the valve closes completely. This appears to be when the leak test is occuring.

This definitely does not appear to me to be a gas cap issue.

Enjoy your vacation. That is a nice area, and the weather looks to be mostly decent next week.