P0440 Trouble Code

[skobie]

Hi everyone. I know there's been pages and pages written on this trouble code, but no matter what I seem to do, the code keeps coming back on and I'm banging my head off the wall.

I have replaced:
1.) Fuel Pressure Sensor (on gas tank and there's only one)
2.) The Vent Valve (located in back near gas tank and Evap canister)
3.) The Purge Valve (located up front on side of engine block)
4.) Gas cap

I've inspected the Filler Neck from the fuel port to the tank and see no cracks or gas seeping wet spots or smell any gas for that matter. So as far as I can tell, the only thing left is the Evap Canister, which costs more than all of the other parts combined and I'm hesitant to spend the money, but need this code to go off to pass NYS Inspection.

Please help as I'm ready to take it to the shop to get fixed since I'm out of ideas.

Thank in advance,
skobie

[rScherzer]

With out the ability to look at data your shooting in the dark. P0440 is a large leak, you probably know all that. I would make sure the vent valve is receiving power or ground from the PCM. If its not commanded on then it would seal the system. Same goes for the Purge valve. If its not getting pulsed from the ECM it wont supply vacuum to the evap system. I would also look at the fuel tank seal to see if its cracked. A smoke test is always the best way but if you dont have that its going to be hard.

[skobie]

rScherzer, what exactly is the fuel tank seal? Do you mean where the gas goes into the tank on fill-up or something else? I have to admit that I hate monkeying with fuel tanks, but will check things out. I'm just not smelling gas fumes anywhere to make me think there's a problem anywhere around the gas tank to filler neck, but let me know where you mean.

Thanks,
skobie

[rScherzer]

Where the fuel pump goes into the tank has a big o-ring seal. I have seen a few leak there. I may be wrong but I think the P0440 would need a leak the size of .040" its really small so its a bit hard to find. If you had access to ecm data you could monitor the FTP sensor. I did some looking you might see if you can google this 05-06-04-014A its a GM doc that mentions a small crack that would be difficult to see at the fuel filler neck on the fuel tank.

[skobie]

I will be sure to look closely around there this weekend, along with the all the EVAP lines. I know it doesn't take much of a leak. If not, I guess it's the smoke test at the shop for me.

skobie