P0440 error code

So I have had this code for some days, I went to AutoZone to get it checked out and the error was:

P0440 - Evaporative Emission Control System Failing

The guy told me the most common thingg this happened was because a misplaced gas cap (not my case) or a cracked seal on the gas cap. He checked my gas cap and the seal was cracked so he recommended I bought a new one. I did for like $10.

So I reset the computer code by myself by unplugging the battery and like 2 days later the light came on again. I went to AutoZone again and the same code. Obviously it isnt the gas cap.

Could anyone help me figure out what could be wrong?

Car: 2001 Pontiac Firebird V6 3.8L

Thanks.

Check your fuel pressure to make sure its within specs. That could can also be cause by lower than normal fuel pressures. I set that code on my 96 Achieva when one of my injector O ring was leaking fuel.

How can i check that?

Could anyone please help me with this?

Any help is appreciated.

To check your fuel pressure, you need a fuel pressure gauge and just screw it onto your schrader valve on your fuel rail. You then turn the ignition on and make sure it built up pressure and that it doesn't drop off until several minutes. Then you start the car and moniter Idle and high RPM pressure, idle should be somewhere around 37 - 40 PSI and WOT's will be around 43- 47PSI. If the pressure is out of range or the pressure is not holding. Its a fuel delivery issue.

Such as old O rings or faulty fuel pump, or fuel pump check ball or the fuel filter could be clogged. You could also just have a bad sensor.

i would replace the fuel filter and run injector cleaner in it.

Hello there!

Don't bother checking fuel pressure! This will only cause a lean code. P0171. What you have is a Code PO440- "Canister purge system (EVAP) has a leak."

Basically the system that holds fuel vapors for emission purposes has a leak. his code will set if the system can’t achieve the desired vacuum or if the system fails to hold a vacuum. No MAP, Inlet air temperature,
throttle position crank position or oxygen sensor codes present. A faulty fuel level sensor can cause a false code, because the PCM will default to 40% fuel level if the fuel level sensor is bad. The EVAP solenoid must pass vacuum when it is turned on.

Look for cracks rips or tears in the fuel vapor hoses from the gas tank to the engine. You might need to get the system smoked to find the leak.
If nothing is found, I would rec to replace the purge solenoid and vent solenoid.

Good luck!

AMEDEE ASE MASTER TECH L1 CERTIFIED

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Thanks