Evaporative Emission Problems.

Posted by Matthew Schroeder on

P0441 / P0442 / P0443 / P0446 / P0455 / P0456: Code are all related to the evaporation emission system. The system periodically test that the fuel system sealed from the outside world. This system consist of an air pump and pressure transducer assembly that pressurizes the fuel tank and a Purge Solenoid that vents the pressure into the intake when the test is completed. It takes a few drive cycles for the computer to be satisfied that everything is OK. So, there is a delay before the system shows that all emission systems are ready as far as the emission testing is concerned.There are not too many places in the system that are problematic. I'll discuss them in order of how often we encounter them here at Rotary Performance.

First, the purge solenoid. The plumbing and electrical connections are pretty trouble free, but the solenoids themselves do fail. The resistance between the two terminals should be around 30 ohms. Above 40 ohms or so, the computer detects that they are faulty. This solenoid is in plain sight near the oil filler neck.

Second, there are air leaks in the system. Sometimes you get small, medium, or large evap. leak codes from the computer. The classic problem is the gas cap. The cap has a check-valve in it and should allow air to flow into the tank through the cap, but air should not be allowed to escape. Also, the o-ring can fail to seal. Beyond that, the next most common place for evaporation emission leaks is from the threaded rings that hold the fuel pump and level sending units in the fuel tank. When they fail, they will have cracks on their sides. This allows them to stretch and keeps them from compressing the o-ring seals enough to seal the covers to the tank. Of note, there is a level sending unit under each tank. Sometimes, these are simply not tightened sufficiently. An easy test is to fill the tank completely and look for fuel leakage on top of the tank.

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