2005 Boxster 2.7L Manual transmission
I am trying to diagnose the problem of not being able to fill more than 2 gallons of fuel without it spitting back at me. Just to start, I've tried:
1. the "turn the filler nozzle sideways / upside down" trick ---> does not work
2. multiple gas stations with different types of vapor recovery nozzles ---> does not work
Background: I've owned the car for approximately 10 months. It has always been difficult to fill. Lots of stopping / restarting of the fill process but recently gotten worse whereby fuel is making its way back up the fill tube and spraying out of the neck filler. Not cool.
High level diagnosis: air is not being evacuated from the tank during fueling.
I have no DTC's and no issue in starting, drivability, etc.
I have read the previous discussion on this subject here:
I have also read similar issues on other sites including two official tech training videos on the EVAP system including the subject of ORVR (Onboard Refueling Vapor Recovery).
Most issues discussed on other sites relate to trouble code concerns usually landing on the common purge valve issue where it fails in the open position (relating to too rich, too lean, fuel trim issues, etc.).
None of the training was 987 specific as each manufacturer has to package their own systems of parts to meet the emission requirements but the basic concepts remain the same.
Here's where I have examined / tested my system.
1. Removed the tube from the tank vent to the charcoal canister and blew air through it - clear, no issue
1. Blew low pressure air down through the filler neck and witnessed air coming out of the top of the fuel tank vent - clear, no issue
2. Removed the charcoal canister and blew air into the inlet - clear, no issue, no charcoal bits or pieces found anywhere, smell of canister was very faint of gasoline (so I assume it is not saturated)
3. Examined the LDP (leak detection pump) and wiring, appears clean with no issues, air filter is like new clean.
4. Separated the purge valve from the forward cabin (connects at rear of cabin low, driver's side USA) and blew air from the carbon canister outlet connection to this rear port - clear, no issue.
5. Removed the purge valve and its related tubing from the air intake down to the rear port
5a. Tested the purge valve actuation via Durametric before disassembly (clicked open, no issues) and on the bench under vacuum (same, no issue), electrical resistance measured 24.4ohms
5b. Ordered new purge valve for replacement anyways (due to pain of removal, not risking a future failure of a 17 year old component and having to go back in there)
5c. Completely disassembled the purge valve and noted no trouble found in any physical internal components, retested electrically and watched the unit operate correctly sans plastic housing.
5d. Blew air into the remaining tubing leading from the rear port to the air intake - clear, no issues.
6. Replaced charcoal canister connecting it only to the fuel tank and went to the gas station - filled fine up to 2 gal and then continued to fill "full blast" until a total of 6 gal was added to the tank - no issues.
Since this last step worked with an open atmosphere vent in an otherwise closed system I now suspect that I have not identified all of the venting that occurs during the ORVR process. I believe this vent, generically called the vent solenoid, is a part of this part on the top of the fuel tank:
Does anyone have any more info on this component or how the ignition off, power off refueling sequence works to move tank pressure and allow fill-up on the 987 platform?
Thanks to all who have gotten this far! Jim