Evaporative system operation help - Jeep Compass Forum
 
LinkBack Thread Tools Search this Thread
post #1 of 5 Old 08-12-2013, 04:01 PM Thread Starter
Junior Member
 
Join Date: May 2013
Posts: 8
 
Garage
Evaporative system operation help

Hello All,
I enjoy running through the posts here but have not seem to find one that will help my situation. I was wondering if anyone can explain the theory of operation of the Evap System. I have a 2007 Compass, 2.4 5-speed 4x4 with 111k on it. I randomly keep getting the check engine light once a week and have to keep shuting it off. Sadly I forgot to write the code numbers down but one is "Gross System Evap Leak" and the other is "Small Evap System Leak". I am sure they are related as they keep coming up togather. I have checked the gas cap multiple times and it is on. Also the filler neck does not appear to be rusted through. Nothing as far as hoses that I can see appear to be off or cracked. Can anyone shed any light on the matter? Many thanks.
moparmonk is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 08-13-2013, 06:37 PM
Senior Member
 
JeepCares's Avatar
 
Join Date: Apr 2012
Posts: 390
 
Here's information from the Factory Service Manual (FSM):
(this might be a case of too much information - hopefully someone will jump in here - I'm not a technician)

P0455-EVAP SYSTEM LARGE LEAK
Theory of Operation
The Evap Purge Monitor tests the integrity of the hoses/tube between the throttle body/intake and the fuel tank. The monitor is a two stage test and runs only after the Evap system passes the small leak test. Stage one is non-intrusive. The Powertrain Control Module (PCM) monitors the purge vapor ratio and the Evaporative System Integrity Monitor (ESIM) Switch closed ratio. If the purge vapor ratio is above a calculated value, the monitor passes. If the ESIM switch closed ratio is greater than calculated value when purge flow is greater than a minimum value, the monitor passes. Stage two is an intrusive test and runs only if stage one does not pass. The PCM commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The ratio is compared to a calibrated specification. If it is less than specified, a one trip failure is recorded. This test can detect if the purge hose is off, obstructed, or the purge valve is not operational.

When Monitored:
With the engine running, during a cold start test with the fuel level above 12%, ambient temperature between 4 C and 32 C (39 F and 89 F) and the fuel system in closed loop. The test runs when the small leak test is maturing.

Set Condition:
The PCM activates the Evap Purge Solenoid to pull the Evap system into a vacuum to close the ESIM Switch. Once the ESIM Switch is closed, the PCM turns the Evap Purge solenoid off to seal the Evap system. If the ESIM Switch reopens before the calibrated amount of time, a large leak error is detected. Two Trip Fault. Three good trips to turn off the MIL.

Possible Causes
EVAP PURGE SOLENOID VACUUM SUPPLY
EVAP PURGE HOSE/TUBE OBSTRUCTION
EVAP SYSTEM LEAK
EVAPORATIVE SYSTEM INTEGRITY MONITOR (ESIM) SWITCH

P0456-EVAP SYSTEM SMALL LEAK
When Monitored:
With the ignition off, fuel level less than 88%, ambient temperature between 4 C and 43 C (39 F and 109 F).

Set Condition:
As temperatures change, a vacuum is created in the fuel tank and Evap system. With the Evap system sealed, the Powertrain Control Module (PCM) monitors the ESIM switch. If the ESIM switch does not close within a calibrated time, an error is detected by the PCM. One Trip Fault. Three good trips to turn off the MIL.

Possible Causes
EVAP PURGE SOLENOID VACUUM SUPPLY
EVAP PURGE HOSE/TUBE OBSTRUCTION
EVAP SYSTEM LEAK


Emissions Control/Evaporative Emissions/SWITCH, Evaporative Emissions System Monitor/Operation

The ESIM (Evaporative System Integrity Monitor), while physically different than the NVLD system, performs the same basic function as the NVLD does - controlling evaporative emissions. The ESIM has been simplified because the solenoid used on the NVLD is not used on the ESIM.

The ESIM consists of housing, two check valves (sometimes referred to as weights), a diaphragm, a switch and a cover. The larger check valve seals for pressure and the smaller one seals for vacuum.

During refueling, pressure is built up in the evaporative system. When pressure reaches approximately .5 inches of water, the large check valve unseats and pressure vents to the fresh air filter.

Conversely, when the system cools and the resulting vacuum lifts the small check valve from its seat and allows fresh air to enter the system and relieve the vacuum condition. When a calibrated amount of vacuum is achieved in the evaporative system, the diaphragm is pulled inward, pushing on the spring and closing the contacts.

The ESIM conducts test on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks.

The ESIM weights seal the evap. system during engine off conditions. If the evap. system is sealed, it will be pulled into a vacuum, either due to the cool down from operating temperature or diurnal ambient temperature cycling. When the vacuum in the system exceeds about 1” H20, the vacuum switch closes. The switch closure sends a signal to the GPEC1. In order to pass the non-intrusive small leak test, the ESIM switch must close within a calculated amount of time and within a specified amount of key-off events.

If the ESIM switch does not close as specified, the test is considered inconclusive and the intrusive engine running test will be run during the next key-on cycle. This intrusive test will run on the next cold engine running condition.

Conditions for running the intrusive test are:

After the vehicle is started, the engine coolant temperature must be within 10 C (50F) of ambient to indicate a cold start.
The fuel level must be between 12% and 88%.
The engine must be in closed loop.
Manifold vacuum must be greater than a minimum specified value.
Ambient temperature must be between 4 C and 37 C (39 F and 98 F)and the elevation level must be below 8500 feet.
The test is accomplished by the GPEC1 activating the purge solenoid to create a vacuum in the evaporative system. The GPEC1 then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the switch does not close, then a general evaporative failure is recorded. The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Even when all of the thresholds are met, a small leak won’t be recorded until after the medium/large leak monitor has been run. This is accomplished by the GPEC1 activating the purge solenoid to create a vacuum in the evaporative system. The GPEC1 then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the medium/large leak test runs and the ESIM switch doesn’t close, a general evaporative test is run. The purge solenoid is activated for approximately 10 seconds, increasing the amount of vacuum in the system. IF the ESIM switch closes after the extended purge activation, a large leak fault is generated. If the switch doesn’t close, a general evaporative system fault is generated.

The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Stage one of the purge monitor is non-intrusive. GPEC1 monitors the purge vapor ratio. If the ratio is above a calibrated specification, the monitor passes. Stage two is an intrusive test and it runs only if stage one fails. During the stage two test, the GPEC commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The vapor ratio is compared to a calibrated specification and if it is less than specified, a one-trip failure is recorded.

The ESIM switch stuck closed monitor checks to see if the switch is stuck closed. This is a power down test that runs at key-off; when the GPEC1 sees 0 rpm’s, the purge solenoid is energized for a maximum of 30 seconds, venting any vacuum trapped in the evaporative system. If the switch opens or was open before the test began, the monitor passes. If the switch doesn’t open, the monitor fails. This is a two-trip MIL. The star scan tool can be used to force the ESIM switch stick closed monitor to run.

The GPEC1 also uses the ESIM to detect a loose or missing gas cap. The GPEC1 controller looks for a change in the fuel level (25% minimum) and then gas cap is loose or missing. If a medium/large leak is detected, a loose gas cap light illuminates and a pending one-trip fault code is set. On the GPEC1, this is a three-trip fault before the code matures.


What you could do without any special tools:
Visually and physically inspect the entire Evaporative Emission System for any of the following conditions:
Holes or cracks
Loose seal points
Evidence of damaged components
Disconnected components
Incorrect routing of hoses or tubes
Loose or missing fuel filler cap
Improper installation of the fuel filler cap
Damaged locking tabs on cap and/or fill tube
Damaged seal points on cap and/or fill tube
Fuel cap gasket seal missing or damaged

Other places to check for leaks:
Recirculation Check Valve
Vapor Recirculation Line
Signal Vapor Line for FVM
Flow Management Valve
Fuel Tank to Canister Vapor Line
Fuel Tank Vent (Check Valve)
Vapor Line to Canister
Flow Control Orifice
Control Valve
Liquid Trap
Fuel Tank
Check Valve
Fuel Fill Tube to Tank connector
Fuel Fill Tube
Filter
ESIM Switch
Canister Vent Line
Evap Canister
Chassis Purge Valve
Fuel Tank to Canister Vapor Line connection
Evap Purge connection
Evap Purge Vacuum Line
Connection to Chassis Line
Connection to Canister
Chassis Purge Line
Evap Purge Vacuum Line
Connection to Evap Purge Harness
Chassis Evap Purge Line connection to Engine Vacuum
Evap Purge Valve
Service Port

Last edited by JeepCares; 08-13-2013 at 06:46 PM.
JeepCares is online now  
post #3 of 5 Old 08-13-2013, 09:24 PM Thread Starter
Junior Member
 
Join Date: May 2013
Posts: 8
 
Garage
Thank you JeepCares! I was going in to post I just scanned it came up with P0455 code. Obviously you guessed that. I guess I have my work cut out to figure this one out. Anybody else narrow it down to something that is common? Thanks all.
moparmonk is offline  
Sponsored Links
Advertisement
 
post #4 of 5 Old 08-13-2013, 09:57 PM
Senior Member
 
tripplec's Avatar
 
Join Date: Mar 2010
Location: Belleville, ON, Canada
Posts: 1,897
 
A lot depends on if and what may have been changed on the vehicle prior. Got gas the day be for example. It could be the gas cap. Remove and it and close it on tightly again (it wratchets). Look at the list and check the easy stuff like hoses for damage or pulled off.

If the problem is or was a glitch and/or gas cap it will clear the code within a day usually if used a few times and the tests pass.

Jeep Compass 2009
4x4, 2.4L, CVT
North Edition
heated seats, TPMS
General Altimax RT43 P225/65R17
Yellow Fog Lamps
CLASS III Curtis Hitch
SOLD @ 153,000km Oct. 2018 THE END !!
Belleville, Ontario, Canada

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
tripplec is offline  
post #5 of 5 Old 07-13-2015, 04:39 PM
wmc
Junior Member
 
Join Date: Jul 2015
Posts: 1
 
Exclamation 2008 Compass

Every time the obd2 is hooked up the codes in order go 0455, 0456, 0455. Sure enough its evap codes. I am wondering if there is a common line that gets replaced more often then all of the area listed. I don't have the $100.00 per hour for diagnostic testing at the auto shop, and I work 40+ hours a week. So with that being said I do not have the time to rip a part the entire thing. Just looking for some common areas of failures. Any and all help much appreciated, and my 4 year old would rather play then fix.
wmc is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Jeep Compass Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome