october2022 - 26

on the vehicle's diagnostic systems to identify
a plugged or failed DPF.
Johnson recommended data analysis.
aftertreatment/engine-related
Mazzon said drivers need to pay more
" Many
failures show themselves at fairly defined
intervals, " he said. " Looking for patterns
of fault codes at certain mileage can give
indications of future potential failures. "
The hurdle here for technicians is
recognizing the signs of an impending
aftertreatment issue, Mustafa said.
" Having the knowledge and experience
to recognize signs of leaking fuel injectors,
coolant issues, leaking DEF and fuel
dosers can go a long way to keep aftertreatment
system-equipped
vehicles
operating reliably. "
The DPF portion of the ATS has been
around the longest, and fleets have gotten
very good at preventive maintenance,
diagnosis, and repair of the DPF and
the related components, Mustafa said.
" Though the SCR system has been around
a while, it seems that failures there are on
the rise, " he explained.
Bressler said following best practices
» Look for patterns of fault codes at certain mileage intervals,
as they could indicate potential failures in the future.
Photo: CanDo International
daily as outlined in the operator's manual
is the best way, and perhaps the only way,
to prevent aftertreatment issues.
A. Duie Pyle monitors soot levels during PM
inspections and each oil change. " If the soot
level reaches a predetermined point, we perform
a forced regen, " Carrano said. " It has significantly
reduced the amount of parked regens the drivers
had to perform during the course of their day. "
Tegels continued. " This is less of a concern when
a vehicle's powertrain is under load. However, the
exhaust temperature will naturally drop if the
duty cycle requires high engine rpms and low-load
conditions such as empty haul backs. Under these
conditions, passive regenerations will decrease,
requiring additional active regeneration cycles. "
" If the soot level reaches a predetermined point,
we perform a forced regen. It has significantly
reduced the amount of parked regens the drivers
had to perform during the course of their day. "
Dan Carrano, VP of fleet maintenance, A. Duie Pyle
As a part of a preventive maintenance
plan, technicians should ensure there are no
exhaust leaks. " You want to maintain that high
temperature so you can maintain that DPF, "
said Tim Moore, VP of TMcare Operations for
FleetNet America.
Moore added that technicians and drivers
should pay attention if they must add coolant, as
it could mean the EGR is starting to leak. " That
coolant is going somewhere, whether it is on the
ground or through the tailpipe, " he explained. " If
that goes downstream and through that DPF filter,
you can have a problem. "
Installing OEM-approved parts, selecting the
correct oil, and/or completing recommended
maintenance practices are vital to extending the
life of an aftertreatment system, Tegels added.
Properly selecting and spec'ing the correct
powertrain can be just as crucial to an emission
system as proper maintenance. " Powertrains
with manual transmissions and/or higher rear
axle ratios typically run higher engine rpms, "
26 Fleet Maintenance | October 2022
In addition to low-load drive cycles, stop-andgo
cycles can be a challenge due to low exhaust
temperatures, which limits the system's ability to
perform passive regenerations, requiring a higher
frequency of active regens. That is an issue
for trucks operating in an urban environment,
Carrano said
" The exhaust aftertreatment system is really a
one-size-fits-all system designed for an on-highway
application where it is running at a constant speed
and temperature. That is where it performs optimally, "
Carrano said. " When you put that on a truck
operating in a stop-and-go urban environment with
a lot of low-load, low-temp operating conditions,
it doesn't get hot enough to turn the soot to ash. "
Educating drivers
Driver behavior is also critical. Moore said one
of the biggest issues is drivers not completing a
regen when needed. " If you pause it or don't do it,
you get a clogged DPF, " he said.
attention to vehicle behavior and dashboard
displays. " Most of the time, the
drivers ignore the warning messages
related to the aftertreatment system
until the truck enters into derate mode, "
he explained. " At this point, the performances
of the vehicle are limited, and it is
necessary to drive the truck to the closest
shop to have it fixed. "
One of the more common issues is failing
to maintain a proper DEF level. If the
DEF tank is low on fluid or has improper
levels, EPA dictates OEMs restrict that
engine. " All of this can be monitored
remotely, " Hopkins stated. " In seconds,
the fleet will know you will have a power
loss within seven hours if you continue
running this way. "
Hopkins also noted that drivers must
use the right fuel. " We've found there are
some places where they are running higher-sulfur
fuel, " he said. " If you're on-highway,
go to any truck stop and there won't
be a problem; but if you're off-highway, you
could end up running some higher-sulfur
fuel. You want to make sure you're
running the right fuel for the application. "
Copeland said poor fuel quality is an industry
issue, mostly due to a lack of standardization-
particularly in the stability of biodiesel fuels.
When improperly stored or contaminated, DEF
can cause aftertreatment system issues, specifically
in the SCR system, Mustafa warned.
Drivers often ignore the initial level or quality
warning because the engine feedback is mild,
Bressler explained. " Once the more serious warning
is received, it may take several drive cycles
after the incident for the warning and engine
feedback will abate, " he said. " If prompt action is
not taken, even when the driver eventually fills
the DEF tank or takes other appropriate action,
the warning may persist, putting the driver in
the position of either admitting bad behavior or
blaming the system. "
Old habits can also create a problem. " There
was a time when idling a vehicle only posed a
threat to maintaining good fuel mileage. On the
modern truck, idling or pulling very light loads
can cause the diesel oxidation catalyst to face plug,
preventing an effective regen from taking place, "
Mustafa noted.
High idle times require an increased frequency
of active regens, which can take 45 minutes
to complete. Bressler said operators sometimes
choose to skip or delay parked regenerations
because it detracts from productivity.
Freeman recommended fleets run manual
regenerations as often as needed, and he advised
drivers to stop and do a regen when the light
comes on. " The purpose of doing a regen is to
reduce the soot level, " he said. " If the light is on,
save yourself time and worry down the road and
let the regen go through its process. It is going
to save you a lot of heartache and hassle down
the road and keep your truck out of the shop. "
For related content go to
FleetMaintenance.com/in-the-bay
http://www.FleetMaintenance.com/in-the-bay
october2022

Table of Contents for the Digital Edition of october2022
