Gas Tank Pressure Emissions Failure

[Coz]

Took my wife's NSX through emission testing on Sat, it passed all the run tests with flying colors.
But...failed the Gas Tank Pressure test.
The car had a Nitrous set up on it, removed it completely today and everything is plumbed correctly.
I don't have the testing cap and pressurizing equipment the emissions testing facility has to pressurize the tank, so I drove it around for awhile and then loosened the gas cap to see if there was any back pressure and there is none.
There is no broken lines and no gas leakage....
Any idea's ?
Thanks.
Jim

 

[D'Ecosse]

Replace the cap!

 

[Coz]

Tried that already....Not the problem. But thanks for the thought....

When the emission testing is done, they use their own special cap that has a hose in the center of their cap which is used to pressurize the tank. My gas cap has nothing to do with their testing.

Tracing things down, I'm thinking it's either the Two Way Valve,
Purge Cut-Off Solenoid Valve or the Purge Control Diaphragm Valve...or a combination of them that have gone south.....

Replace the cap!

 

[Larry Bastanza]

Has the car had any body work? Any chance the left rear quarter has been R&R'ed? Sounds like the filler neck or the vent hose may be missing a clamp.

Just a guess.

Regards,
LarryB

 

[Coz]

Not that I know of, previous owner says no, car fax report is clear.
Guess I'll pull the quarter panel to find out....
Thanks Larry.

Has the car had any body work? Any chance the left rear quarter has been R&R'ed? Sounds like the filler neck or the vent hose may be missing a clamp.

Just a guess.

Regards,
LarryB

 

[Briank]

Pulling the quarter panel is unnecessary the clamps are accessible from the engine bay but you will need to pull the air filter housing, and the coolant tank

There is a lot of plumbing in the vapor recovery side of the fuel system. I had a bad seal on the fuel petcock on the top of the tank. I was getting a strong smell of fuel on hard left turns had to drop the tank to diag. and repair. You should be able to connect a low pressure air supply and then listen for leaks.

 

[Coz]

Will tape off the gas tank nozzle, pressurize it some and listen to see what I hear.
Thanks Brian...

There is a lot of plumbing in the vapor recovery side of the fuel system. I had a bad seal on the fuel petcock on the top of the tank. I was getting a strong smell of fuel on hard left turns had the drop the tank to diag. and repair. You should be able to connect a low pressure air supply and then listen for leaks.

 

[Coz]

Here's what I found out just now. Taped off the gas tank nozzle and pumped air into the gas tank. Can hear air escaping from the passenger side, bulkhead area of the motor compartment, seems to be coming from below the valve cover. Now I know where, got to find out what....