Fleet Maintenance - 34

meaning there is too much fuel or too little fuel,
respectively - this can cause the combustion
process to be less efficient.
"If 'X' amount of air goes in the engine, the
fuel is supposed to match that depending on the
load that is being delivered," says Barry Hoyland,
owner of Vehicle Service Solutions of California
(VSSCA), a repair center that specializes in
emissions and diagnostic services. "If there's an
air-to-fuel ratio problem, it's likely due to the fuel
not being delivered properly. That's an indicator
that there's a problem with the injection."
Hoyland also provides consulting services for
fleets and government agencies to improve their
operational efficiencies.
Visible and audible signs that indicate fuel
injection system issues include an illuminated
malfunction indicator lamp (MIL), sometimes
referred to as a "check engine" light; rough or loud
vehicle idling; hard starting, engine misfires,
visible smoke, acceleration issues, and/or loss
of performance. Additionally, increased emissions, engine oil dilution, or fuel in the engine
crankcase would also indicate a fuel injection
system issue.
When one or more of these signs are noticed,
it is important to inform the fleet's technician to
properly check and diagnosis the issue.
In late-model trucks with aftertreatment
systems, if the issue is too severe the truck will
derate and eventually shut down, Hoyland notes.

Equipment needed to diagnose

Technicians may use a variety of tools to diagnose
issues with the fuel injection system, depending
upon the symptoms the vehicle is showing and
the model year of the vehicle.
Vehicles built before 2000 generally don't have

VehicleServicePros.com/10094365

34 Fleet Maintenance | April 2020

»A visual sign that indicates a fuel injection system issue could be an illuminated "check engine" light.
124455342 | Rumess | Dreamstime

extensive vehicle computer technology, whereas
models manufactured after 2000 do. These newer
vehicles allow technicians to use a modern-day
scan tool, VSSCA's Hoyland says.
In addition to a scan tool, to test fuel injection
issues technicians may need an oscilloscope,
digital voltmeter, and thermal imaging camera,
as well as exhaust gas sampling and fuel pressure and volume testing.
A scan tool with bidirectional control allows
technicians to perform a cylinder balance
test, but a cylinder cutout
test would be most useful,
Hoyland says. These tests
allow the technician to
disable, or cut out, a cylinder
while the engine is running at
a specified rpm to find the one
that has a fault.
"Some scan tools will actually give you a cylinder contribution all the time so you
can see how each cylinder
is operating," Hoyland says.
"[The scan tool] does that by
measuring crankshaft speed.
If you have one cylinder that
is not contributing as much,
then the crankshaft actually
slows down after that cylinder
is fired, so you can see what
cylinder is misfiring based on
crankshaft revolution."
A thermal imaging camera
enables the technician to
look at the exhaust manifold and each cylinder at
the exhaust port. The tool
measures the temperature of the exhaust coming
out. If a cylinder is being

"The major cause
of failure on
[fuel injection]
systems is lack of
maintenance, or
some kind of selfinduced failure
where [technicians]
were changing
the fuel filter and
debris entered
the system."
Mike Cleary, Owner, Cleary Automotive,
and ASE master heav y truck technician

over- or under-fueled, the thermal imaging camera will indicate a difference
in temperature.
In addition to equipment, using the vehicle's
information such as wiring and repair diagrams
as well as fuel pressure requirements is also
important to review, Hoyland adds. This information is available through the engine and/or
truck manufacturers, as well as many repair
information sources.

http://www.oileater.com http://tiny.cc/v6g42y http://www.VehicleServicePros.com/10094365

Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance