CLAS AC 0410, Руководство пользователя, Страница: 20 / 24

AC 0410
SMOKE LEAK DETECTOR
• Fuel Vapour Recovery System (EVAP)
According to the Environmental Protection Agency, the EVAP system is the most neglected
of all automobile emission systems. A leak as small as 0.5 mm in diameter can let more
than 30 times the amount of pollutant allowed into the atmosphere. In addition, leaks
from the EVAP system can be a major cause of engine light indicator (MIL). In the past,
problems with the EVAP system have been difficult to locate and repair. They can now be
quickly diagnosed and repaired, becoming a cost-effective entry ticket for workshops.
There are several acceptable methods of inspecting the EVAP system. Typically, we must
close all ventilation solenoids, fill the system with smoke and look for smoke escaping at
the leak. Since these systems vary from car to car and have evolved over the years, we
will attempt to describe the operating guidelines that should be useful in inspecting these
EVAP systems.
Beginning in 1996, cars were equipped with a plug for connection to the EVAP system. The
port is usually located under the hood, but it may be located elsewhere on the automobile.
To access this port for testing, remove the cap, then remove the Schrader valve from
inside the service port using the Schrader valve removal tool provided. Important Note :
The Schrader valve has a left-hand thread, turn clockwise to remove it!
On-board diagnostics on vehicles from 1996 and beyond will determine if there is a leak,
the following trouble codes may be used to report the leak: PO442 for a 1mm leak PO456
for a 0.5mm leak.
1. Using a diagnostic tool, close the vent solenoids so that the EVAP system is airtight
to the atmosphere.
2. Set the unit for operation.
3. Remove the tank cap and start filling the system through the EVAP system
connection socket until you see dense smoke coming out of the neck of the tank.
This procedure ensures that the system is full of smoke. Replace the tank cap and
continue injecting smoke into the system.
4. Inspect under the hood for leaks using a light. Drive the vehicle on deck and
inspect the underside of the car, following the EVAP system route.
5. When the system fills with smoke and the pressure in the system equalizes,
monitor the flow meter and pressure gauge. If there are no leaks in the system,
the pressure gauge reaches its maximum pressure and the flow meter drops to
zero. Otherwise, the flow meter will indicate the size of the leak. Refer to the
result of the leak size identifier.
6. Once the leak has been located and repaired, it is advisable to repeat the above
procedure using air only. It is not necessary to light the smoke to test the leak
using the flow meter. Replace the Schrader valve and cover. (Note: the valve is
left-hand threaded).