September_2021 - 32

complaint of poor driveability, poor idle,
etc. He explained to us that he had just
had the engine rebuilt and it has never
run right since. We examined the vehicle's
engine performance and began performing
analysis and all along the way we documented
our findings (Figure 2).
After we acquired a running compression
test, we began to analyze the
data. One of the first observations we
made was that the actual spark event was
taking place at 5.4 degrees BTDC and
not at the 14-degrees BTDC indicated
by the timing light and marks. The valve
timing events were measured and noted.
Additionally, the idle compression peaks
were observed at 110 psi, which is high
but assumed acceptable based upon the
engine performance modifications.
Based upon our findings, we recommended
installing the correct spark
plugs, set the ignition timing using the
in-cylinder pressure method, and fine
tune the air-fuel ratio across the engine
operating range.
The customer contacted us a few
months later to tell us that the vehicle has
been running fine and that the fuel mileage
went from 10 mpg to 14 mpg but was
concerned that the engine had low compression
based upon our data. We proceeded
to explain to the customer that a
running compression test is usually 60 to
65 percent of what one would observe during
a cranking compression test (Figure 3).
Performing documentation like this
indeed can take additional time but, in
the end, it's well worth it. The documentation
is the story that illustrates exactly
what happened as a vehicle entered the
service center, what was done, what
wasn't done, and what was recommended.
Some shop management systems make
it very easy to integrate their inspection
items and subsequently include additional
rich assets alongside descriptive
text. Some applications can be accessed
by using a smartphone or tablet which
allows a technician to use the voice-totext
feature instead of typing out a long
story. Initially this may take a little bit of
practice but once you get this down, it
becomes easy to handle. Many scan tools
p Figure 3 - Running compression test (ignition timing check)
and diagnostic equipment on the market
today are web connected which can be a
good thing, especially if the device has
a web browser and your shop is using a
shop management system that can be
accessed through the web.
MODERN TOOLS
During every maintenance service at my
shop, we perform a vehicle health-check
scan of all modules for diagnostic trouble
32 PTEN SEPTEMBER 2021 www.VehicleServicePros.com
codes (DTCs). We take that report and
digitally attach it to the repair order.
Most of our scan tools today are PC/
tablet based and have web access which
allows us to move the report right into the
notes section of the repair order quickly.
In most cases the scan tool will output the
report as a PDF that is then attached to
the invoice digitally. Recently, I discovered
that the Bosch 525X and 625X can
automatically place the results of a vehicle
p Figure 2 - Case study invoice documentation
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September_2021

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