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Failed Smog Test

1985 Chevy Camaro Failed LPFET EVAP Test

Hello. I have a 85 Chevy Camaro v6 2.8l and it passed the smog check except the EVAP test. The gas tank pressure test part of the smog test failed. If you had any tips that would really help. Thank you.


Sounds like your Chevy Camaro failed the LPFET (Low Pressure Fuel Evaporative Test). The Low Pressure Fuel Evaporative Test (also known as the EVAP test) ensures that there are no leaks in-between the hose leading from the Gas Tank to Charcoal Canister, or for that matter anywhere raw fuel (gasoline) exists. 

The LPFET involves the smog technician clamping the end of the hose leading to the charcoal canister and pressurize the gas tank with Nitrous Oxide via the LPFET test tool. The tool will then calculate the drop in pressure due to any leaks. Technically there should be very little drop in pressure once the EVAP system (gas tank) is pressurized. 

In order to fix your Chevy Camaro's EVAP failure it will be necessary to locate the leak and repair the line. Depending on where the leak is located, this repair may be cheap or expensive, but the first step is to find where the leak is at. The gas cap test is conducted on a separate test machine which is attached to the smog check machine. The gas cap test is not part of the LPFET.

Trace the EVAP vapor hoses in-between the fuel tank and the carburetor. Look for brittle, broken, and/or disconnected hoses.

posted by SmogTips Support 04-07-2014 12:23 PM

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