Faults in the Vapor Recovery System

[porsche996tt_tpe]

Hi Everyone:

I'm asking this for a local repairman who got stock on the Vapor Recovery System...

The car is a 2007 997 Carrera 4S with 60K KM on it.

The PIWIS faults are : P0456 "Evaporative emission system leak detected (very small leak) and P0455 "Evaporative emission system leak detected (large leak).

The mechanic has replaced the 1. gas vapor recovery tank, 2. the solenoid (I guess a valve on the engine's intake end), 3. gas cap, 4. the connecting hoses checked for leak. None of these steps corrected the faults. The faults were reset but would re-appear after couple of days driving.

He's clueless as to what else can go wrong. Help from anyone?

Thanks!

CW

[spiffyjiff]

hmmm, looks like he correctly tried to hit all the "possible causes" but unfortunately to no avail:

P0455

Leakage in fuel tank system

Diagnostic conditions

--Vehicle speed = 0 km/h

--Engine speed = 0 rpm

--Correction factor, height > 0.73

--Coolant temperature upon starting the engine may be no more than 6.8 K above ambient temperature

--Coolant temperature when engine starts > 3.8 °C

--Period for which the engine needs to have been running before ignition is switched off > 20 minutes

--Ignition has been switched off for at least 10 seconds.

--Ambient temperature 4 … 35.3 °C

--Active charcoal filter load < 3 for minor leak

--Fuel tank fuel level 10 … 54 litres

--Battery positive voltage 11.02 ... 14.5 V

--No fuel tank filling

--No faults detected for ambient pressure sensor, coolant temperature sensor, vehicle speed sensor

--No output stage faults detected for DMTL pump motor, DMTL switch-over valves and tank vent

--No fault detected for tank vent (flow)

The diagnostic conditions can also be established using the PIWIS Tester via the short test "tank leakage test". After the test has begun, the ignition must be switched off.

NOTE

--In this context, please also observe the function description.

Possible fault causes

--Tank cap not closed correctly, leaking or missing

--Purge air line leaking

--Tank vent leaking

--DMTL (Tank Leakage Diagnostics Module) leaking

[porsche996tt_tpe]

Thanks, Spiff, the only thing he's not done is replacing the gas tank itself... What is the "Tank vent leaking"? What to check on this item?

BTW, I know on older cars they'd by-pass the gas recovery system, but on 997, is it possible? If so, what's to look out for and how is it done?

[JFP in PA]

Thanks, Spiff, the only thing he's not done is replacing the gas tank itself... What is the "Tank vent leaking"? What to check on this item?

BTW, I know on older cars they'd by-pass the gas recovery system, but on 997, is it possible? If so, what's to look out for and how is it done?

The tank "vents" to the EVAP system, it is a closed loop arrangement that captures vapors and then burns them in the engine. Do a search, it is a common headache area for vacuum leaks. By-passing it is going to be a problem as the DME uses sensors to make sure it is functional, and they source of your codes. Disconnecting it is going to leave the car in permanent code conditon, so it may fail inspection (It is required for state and fed emissions regs in the US and many other countries).

[porsche996tt_tpe]

Thanks JFP for the help. I look at http://www.obd-codes.com/p0456 and that of the P0455 and understood the system now.

Can anyone help me locate a diagram showing how the EVAP system is connected? An exploded chart or any diagram showing all the parts will be great!

Thank you all.