re: #196 Justanotherhuman

I hope the fix is easy, car is just broke in!! saturnfans.com

I had my Service Engine Soon light come on about two weeks ago. I scanned it and got a P0440 which is a generic “Evaporative Emission Control System Malfunction”. The auto parts stores will try to sell you a replacement gas cap when this code shows up, and it could be a leak at the gas cap, but that’s not what I found.

There is a very simple emission system diagram on a sticker under the hood. It shows two vacuum lines going to the throttle body (one from the fuel pressure regulator and one from the a purge solenoid.

I capped off the port on the purge solenoid (vented the fuel vapor into the air), reset the code and drove the car. The light never came back on. Therefore I knew that the problem was not at the purge solenoid.

There are two components to the emissions system: canister purge solenoid and canister vent solenoid. The canister purge solenoid (or purge valve) is located between the right end of the engine and the right strut tower. The purge solenoid is normally closed. But when ordered to do so by the PCM, it allows the fuel vapors that are stored in the EVAP canister to be drawn into the intake manifold, where they’re mixed with intake air, then burned along with the normal air/fuel mixture, under certain operating conditions. The PCM-controlled EVAP canister purge control solenoid valve also controls this vapor flow.

The canister vent solenoid is located near the top of the fuel filler neck is part of the EVAP system’s leak diagnostics. The vent solenoid is normally open to allow outside air to flow through the vent, through the EVAP canister and into the fuel tank which maintains atmospheric pressure inside the fuel tank. But when energized by the PCM the vent solenoid closes and seals off the EVAP system for inspection and maintenance tests and for OBD-II leak and pressure tests.

I found that the vent line going from the fuel filler neck to a rubber hose that goes to the tank (or charcoal canister?) was rusted. In fact it was rusted enough that apparently there was a hole in it. I bought some 5/16 brake line and used my tube bender and replaced the rusted tube. I reset the code again and it hasn’t come on since. The rusted line runs right next to the plastic filler tube that goes from the fuel filler neck to the tank.