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Failed Smog Test

1995 Chevy Blazer s10 Fuel Evaporative Controls functional test failed.

How do I fix my Chevy Blazer's EVAP system? It failed the LPFET test.

by viki    11-14-2010 03:37 PM


Let's learn how the EVAP test also known as LPFET (low pressure fuel

evaporative test) was done. The LPFET test is conducted by a BAR approved

Low Pressure Fuel Evaporative Test machine. A pressure hose is connected to

your Chevy Blazer's gas filler. This is where the gas cap goes. Your Chevy's

EVAP system and gas tank is pressurized 0.5-1.0 psi (14"-28" column of

water) and pressure drop measured for 2 minutes. The allowable drop is .40

psi. Anything greater then .40 psi shows a leaking EVAP system. The data is

entered into the smog machine, and your Chevy Blazer fails the smog test.


The EVAP system is designed to prevent the release of gasoline vapors into

the atmosphere. All EVAP systems have one similar component, which is the

Charcoal Canister. The Charcoal Canister stores gasoline vapors from the

vehicle's fuel tank and carburetor float bowl if your car is carbureted,

until the engine is ready to burn them during acceleration or cold starts.

The number one fault which causes vehicle's to fail the EVAP test is broken,

loose or disconnected EVAP fuel lines.


It is necessary to trace the entire EVAP system in order to find the

defective section and/or component. We recommend an experienced smog check

repair center conduct this repair as broken EVAP hoses may be difficult to

find for the average vehicle owner. If you have mechanical experience you

may try to follow the EVAP route yourself.

posted by SmogTips Support 11-15-2010 12:55 PM