GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 78)

INTAKE MANIFOLD LEAKS
When a manifold leak occurs, lean misfires
or low manifold vacuum may be seen. To
locate a leak, run the engine and observe the
HC and CO levels. Spray a small amount of
carburetor cleaning solvent at the potential
leak points and observe the HC and CO
readings. These will rise soon after solvent
is applied to the leak. Work slowly over small
areas to allow the engine and the Gas
Detector's sampling system to respond to the
solvent.
CATALYTIC CONVERTER
The catalytic converter can be tested by
running a warmed up engine at idle for 2-3
minutes and noting the HC level. With the
ignition off, ground the sparkplug end of one
of the sparkplug wires. Restart the engine
and observe the HC measurements. The
cylinder with the disabled spark will pump
raw fuel into the exhaust stream, which will
appear as an increase in HC. The HC will
rise rapidly and hold briefly at an elevated
level. A functioning catalyst will respond to
the HC with an oxidation reaction, and the
HC levels will go down by at least 300 ppm
in less than 30 seconds. If the HC reading
stays at the higher level, the catalytic
converter is not operating efficiently.
ROAD TEST
When diagnosing an emissions failure,
performing a road test before and after the
repairs will provide a comparison between
the emissions before and after any corrective
actions are taken. It is important to duplicate
the road test as closely as possible for good
comparisons to be made. Plan a route that
allows all the actions to be taken and that is
easily repeated.
A sample road test sequence is shown on
the facing page.
Start the Emissions test (or the O2 Sensor
test with Emissions displayed). The recording
function allows the results of the test to be
captured and reviewed. Press RECORD to
begin recording the results. Start the road
test actions: (Rapid acceleration, 30 MPH
cruise, etc.) Press NEXT to mark the
beginning of each phase of the road test. At
the end of the test press PAUSE to stop
recording. The results will stay in memory
ONLY while power is applied. Restart
Emissions and SELECT Examine . The road
test will be played back in real time. The
REWIND and FAST FWD keys can be used
to quickly review the results.
If you need to disconnect power before
making repairs and repeating the road test,
the results should be printed (press
REPORT-AUTOTEST and SELECT
Print
Saved Data.
Make the repairs, and repeat the road test
to verify that emissions were reduced. Again,
the results can be reviewed in real time or
printed using the REPORT-AUTOTEST key.
7-5
D
O
N
OT RUN THE ENGINE FOR MORE
THAN A MINUTE WITH A
GROUNDED SPARKPLUG WIRE
.
E
XCESSIVE HEATING OF THE CONVERTER
WILL OCCUR