3/2/2020

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Solution K25470463
Monday, March 2, 2020 7:38:41 PM CET

** SOLUTION **
Title

Mack Chassis - Emcon (Spark Assist) Engine Aftertreatment System
Troubleshooting Check Sheet - US07 Emissions

Mack Models
Mack Model

LEU , MRU - TerraPro

Emission Standard
Emission Standard

US07

Engine family
Engine family

MP7

** SOLUTION **
Cause

Mack Trucks continues to receive complaints regarding US07 MP7 spark
assist troubleshooting.

Solution

It has been found that on these older chassis it is best to eliminate all the
basics prior to opening an eService case. Pressure test the complete intake
and exhaust systems. There is zero tolerance for leaks in these systems.
Next, go over all the wiring harnesses to see if there are crispy spots No rub
spots, loose areas are tolerated. Next check the chassis air supply system to
be sure the customer has been draining the air tanks nightly and servicing
the air dryer every 6 months with a fresh COALESCING type air dryer
cartridge. This DPF system cannot tolerate ANY water or oil moisture at all
for it to function correctly and reliably. Repair any leaks, electrical and air
system issues before starting to dig into the Aftertreatment system.
Use the US07 Spark Assist Check Sheet here to compare sensor and
component values during fault tracing for spark assisted regeneration
troubleshooting.
Please refer to the reference documentation below.
• TRU Regen Design and Function
• EMCON System Training Overview

Solution visibility

Dealer distribution

Function(s)/component(s) affected
Function affected

EECU , MID 128 – EMS , MID 177 – EMCON , MID 233 – UDS , Diagnostic

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Print Case

tool , Engine , exhaust

Function Group
Function Group

258 emissions after-treatment , 281 ignition coil, spark plug, ignition cable
, 284 control system, fuel supply , 2861 Engine Wiring Harness

Customer effect
Main customer effect

regeneration , diagnostics/methodology , efficiency/abnormal behavior

Fluid implicated

Air , Fuel

Conditions
Vehicle operating
mode
Frequency of
occurrence of problem

when stationary

always

Administration
Author

a175606

Last modified by

RU4469V

Creation date

05-04-2016 17:04

Date of last update

21-02-2020 19:02

Status

Published

UNCONTROLLED COPY. Printed document is for temporary use only and should not be retained.

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DPF Regeneration Companion Sheet (SPN4094 v1730.7)
Spark Assist (Mack only US07)

Before starting diagnosing Regen issues with this system, a thorough investigation of the condition of
the complete chassis needs to be done.
•

•
•

Has the Chassis Air System been serviced correctly base on published service information? If
not, correct the issues. The air dryer needs to be properly connected and the filter serviced
with a recommended Coalescent cartridge. The pressure in the system needs to be regulated
within the correct tolerances. If the dryer system comes in by-passed or inoperative, the air
tanks and lines supplying the aftertreatment system may need to be cleaned out. Otherwise,
the Air Atomization Module (even a new replacement) will not last at all.
Has the fuel system been serviced correctly based on published service information? If not,
inform the operator that the fuel system needs to be serviced.
Is the engine air filter flowing correctly and not plugged? If not, inform the operator that the
filter needs to be serviced.

Combustion Air Flow. 400+ LPM is required during Regen with idle set to 700 RPM for US07.
•

o

US07 - The CAV has an arrow on it to show direction of flow. The orifice in the intake manifold
should be 3/8”. There should be NO orifice at all in the CAV fitting boss at the combustor
housing.
There have been reported instances of replacement US07 combustor housings that had the
US10 9/32”orifices in place at the Combustion Air inlet port of the Combustor Housing. Inspect
new replacement Combustor Housings for an orifice.

Typically, the Spark Assist system will complete a Service Regen even when there is NO combustion
air flow. It will only display Flame Temp readings of only around 1700*F where proper flame
temperature is normally at 1850 – 2100*F. There is typically enough oxygen remaining in the exhaust
stream to support combustion under Service Regeneration conditions. This has fooled many in the past
giving the impression of successful Regens but when under load, on the road, the oxygen from the
engine is all used up by the engine combustion process and Regens will fail under load. So it needs
Combustion Air under these conditions to support successful combustion.
Note that any leaks in the intake or exhaust systems will cause issues. The best way to inspect
for and diagnose leaks is with the smoke test machine. Repair all leaks before proceeding.

Air Atomization Module (AAM) flow chart

Fuel Supply System
100 PSI fuel pressure Nominal. Range is 95 to 105. 95 psi is at the extreme low limit. 94 or less will
give you reliability issues. The fuel pressure is controlled by the Atomization Module (AAM) and not the
pump.
o

o
o
o

o

If fuel pressure is low, remove the fuel return line from the AAM to the fuel tank and
look for the amount of return with the engine running and pump active. Remove the
AAM return line at the fuel tank return tee and cap the tee.
LOW fuel pressure – LOW return flow indicates a bad pump or restriction from the
engine supply to the pump inlet.
LOW fuel pressure – HIGH return flow indicates the pressure control valve in the AAM is
stuck open.
Another indication of the Atomization Module dumping fuel on the US07 engine
platform, is in engine pressure sensor values during a Regen, fuel pressure lower than
40 psi, engine load higher than 15% and slightly lower boost pressure. These are
indications of fuel starvation. This is more important on the US07 engine platform
because the Atomization Modules in this platform do not have pressure sensors and the
Regens are done at idle.
Note: In some cases, drops in engine power have been reported when the system goes
into auto Regens while driving. In most of these cases, the issue is engine fuel

o

starvation due to the Atomization Module pressure control valve stuck open and
dumping fuel pressure. The engine fuel pump cannot keep up with the engine and DPF
fuel demand with this condition, and the fuel pressure drops.
HIGH fuel pressure – LOW flow indicates a blockage in the Atomization Module or the
return line. Test the return flow again at the return fitting at the Atomization Module
this time. If flow returns to normal, the issue is a blocked return line. If the flow
remains low with high fuel pressure, the issues is a blockage within the Atomization
Module.
Air Supply System

120 PSI air system air pressure to the AAM Nominal. 100 to 130 PSI is acceptable.
o

o
o

Less than 100 PSI will cause issues. Pressures over 135 will cause issues. If the pressure is OK
stationary (no Regen), and drops during Regen, there is a restriction in one of the lines, or a
sticking pressure protection/supply valve, or a valve installed incorrectly, or the air supply was
modified by the body builder (we have seen air taken from the wrong tank). The air system
actually does not take all that much air. Atomization air is restricted through the orifices in the
nozzle and the flow should decrease as fuel is injected (sharing the same holes).
On the US07 system the Supplemental Air Valve should only activate momentarily on the initial
system test ( 1 or 2 seconds ) then remain off for a Service Regen.
When checking the fuel spray pattern at the nozzle, with Atomization Valve active and Injector
control active, you should have a heavy white fog. Not a stream of fuel and not a light mist.

Spark Ignition System
o

When checking for spark quality, it should be checked during an active Regen command, not
with the Tech Tool test. For some reason, when tested with the Tech Tool, the pulse rate is
lower (longer coil charge time) than it is during an active Regen. A good test tool to have handy
is a straight in-line spark tester (the style with the light bulb and not the open gap type). Auto
parts supply stores typically sell these for about $7.00.
General Electrical

o

o

On the US07 system, it is recommended to monitor the Emcon module Battery and Ignition
voltage during the system test period when all components are turned on and again during an
active Regen.
There should be no voltage drop at all compared to the battery voltage. The wires from fuses
54 and 64 are adequate but marginal and it does not take much of a resistance problem in the
wires to cause Regen issues.

o

o

54 is the Battery power and 64 is the Ignition power. 54 goes from the FRC connector pin C7 to
the 102 pin connector pin 5, to CDPF connector pin B, and finally to the Emcon A connector pin
A1.
64 goes from FRC connector pin A3 to the 102 pin connector pin 78, to the CDPF connector pin
F, and finally to the Emcon A connector pin A3.

Note that on the US07 the Emcon module will NOT log a fault for open circuits (FMI 5) on the
CAV circuit. This circuit is shared with the Atomization Air Valve. If you get an open circuit on any of
these circuits individually, the other component will take up the load and the module cannot detect the
open circuit condition.

US07 Typical Service Regen with good result

US07 EMCON -- FAILED REGEN CHECK SHEET

CASE NUMBER

CHASSIS MODEL AND SERIAL NUMBER

1

SMART SWITCH INHIBITTED?

2

FAULT CODES LOGGED

(W1949.1)

Y

N
MID

PID

SID

PPID

PSID

FMI

OCCURANCES

3
4
5
6
7
CLEAR ALL FAULTS AND CONTINUE

GUIDED DIAGNOSTICS SYMPTOM-BASED DIAGNOSIS FOR THE FOLLOWING STEPS
19

IDLE SPEED SET TO?

RPM

SHOULD BE SET TO 700 RPM
If the MID177 cannot be read J1587 wire may be removed per
FSB258-011

MID 177 SW PART NUMBER 21429010 OR HIGHER?

Y

N

Y
Y

N
N

23

DP SENSOR HOSES PER SB 234-020?
TEMP SENSORS CORRECTLY INSTALLED
Combustion Air Valve CORRECTLY ORIENTED AND NO
LOOSE FITTINGS OR CONNECTOR

OK

NOK

24

CAV FLOW with engine running and CAV activated

20
21
22

LPM

TOOL PART NUMBER 85112577

READ THE SCRIBE LINE IN THE
MIDDLE OF THE BOBBER

DWYER VFC-132-EC CAN BE
SUBSTITUTED
CAV FLOW with the outlet of the toot to ATMOSPHERE
25

26

SPARK OBERVED IN NOZZLE HOLE

(circle one)

IF NO SPARK OR NOT STEADY - REMOVE 1 SPARK
PLUG WIRE FROM THE COIL, INSTALL AN IN-LINE
SPARK TESTER BETWEEN THE COIL AND THE WIRE
AND TEST AGAIN TO SEE IF THE BULB LIGHTS UP

LPM
STEADY

INTERMITTENT

NONE

STEADY

INTERMITTENT

NONE

See FSB258-011 but do NOT activate the
coil with the wires removed

27
28

FUEL LINES CORRECTLY INSTALLED?
Y
N
Engine Running - Regen Activated - Fuel Valve and Pump Active
FUEL PRESSURE INTO THE ATOMIZATION MODULE
PSI
If fuel pressure is lower than min spec in GD (95 psi) - how much fuel is returning to the tank from the Atomization Module?
NONE
A LITTLE
A LOT
( If NONE ) FUEL PRESSURE INTO FUEL SHUT OFF
Per GD instructions
PSI
( If system pressure ) VOLTS AT FUEL PUMP/VALVE
VOLTS

29

FUEL SPRAY PATTERN

30

AIR PRESSURE INTO THE ATOMIZATION MODULE
FUEL NOZZLE AIR PRESSURE

(CHECK ONE)

FSB258-012

FUEL STREAM
NO FUEL
WHITE FOG
PSI
PSI
PSI
PSI

31
32
33
34
35
36
37

DPF DP READING KEY ON - ENGINE OFF
DPF DP READING AT IDLE
DPF DP READING AT HIGH IDLE
DPF DP READING UNDER HARD ACCEL
FLAME TEMP DURING SERVICE REGEN
BOOST PRESSURE DURING SERVICE REGEN
EGR DIFF. PRESS. KEY - ON ENGINE OFF

KEY OFF
KEY ON - ENGINE RUNNING (master air valve on)
NOTE: over 12 psi requires nozzle replacement
KEY ON - ENGINE RUNNING - MASTER AIR VALVE & CAV ON
Note: During active Regen, Nozzle pressure should be around 60 psi
Note: CAV and Atomization valve open with the same button
PSI
PSI
PSI
PSI
DEGREES F
PSI
PSI

THIS NEXT SECTION IS ONLY TO BE FOLLOWED IF THE SYSTEM DISPLAYS CONDITIONS OF EXTREMELY
FAST SOOT RATIO INCREASE AND CHRONIC COMPLAINTS OF HIGH REGEN DEMAND

38
39
40

41

42

43

WITH INLET PIPE OFF OR FILTER REMOVED
SMOKE LEVEL TRANS IN GEAR - OPERATING ARM
(CIRCLE ONE)
DIAGNOSTICS FOR 'FREIGHT TRAIN BLACK'
WITH EGR VALVE UNPLUGGED STILL SMOKES??
IN NO - DOES EGR DIFF PRESS READING GO UP AND
DOWN IN EGR FUNCTION TEST??
IF NO TO ABOVE DISASSEMBLE THE EGR COLD SIDE
PIPE - UNPLUG EGR VALVE AND FEEL FOR FLOW AT
IDLE - FEEL FLOW??
IF NO TO ABOVE REMOVE EGR DIFF PRESS SENSOR
- TUBES - BLOCKS AND INSPECT FOR
RESTRICTIONS - LEAKAGE - O-RING INTEGRITY
IF EGR SYSTEM OK - CUT OUT CYLINDERS WITH
VCADS TO SEE IF THE SMOKE GOES AWAY WITH
ANY CYLINDER CUT OUT

SLIGHT
HAZE

SOME
BLACK

YES

NO

YES

NO

YES

NO

RESTRICTIONS

LEAKAGE

DOES NOT
CLEAR

CLEARS

FREIGHT
TRAIN
BLACK

OK

44
45
46

THIS SECTION TO BE FILLED OUT IF THE SYSTEM IS LOGGING ACTIVE PSID 249 FMI 9 FAULTS
Manually input MID 128 PSID 57 FMI 4 in Guided Diagnostics for tools and connections for 43, 44, 45
VOLTAGE AT EMCON 18 PIN / PIN A1*
VOLTS
VOLTAGE AT EMCON 18 PIN / PIN A2*
VOLTS
VOLTAGE AT EMCON 18 PIN / PIN A3*
VOLTS
* FOR 5 SECOND WHEN KEY IS FIRST CYCLED ON - this will load the circuit during the self test

Check appropriate box
NOT
REPLACED REPLACED INSPECTED

PART
EMCON
NOZZLE
DPF DP SENSOR
FILTER
ELECTRODES
INLET TEMP SENSOR
FLAME TEMP SENSOR
PRE-FILTER TEMP SENSOR
OUTLET TEMP SENSOR
EMCON MODULE
ATOMIZATION MODULE
FUEL PUMP
FUEL SHUT OFF VALVE
EMCON HARNESS
CJB
COMBUSTION AIR VALVE
J1587 DISCONNECTED?
ENGINE
EGR DP SENSOR
EGR VALVE
CHECKED INTAKE SYSTEM FOR LEAKS
EGR DP TUBES
VENTURI
INJECTOR(S)
INJECTOR PART NUMBERS
BOOST PRESSURE/TEMP SENSOR PART NUMBER
MID 128 REPROGRAMMED
MID 177 REPROGRAMMED

Y/N

Y/N

Y/N
Y/N

System Overview

T1 Temp
Flame T
T2 Temp
T3 Temp

T3

T1 Temp
Flame T
T2 Temp
T3 Temp

T2

Flame

T1

T2 Temp

T3 Temp