ISUZU NPR Truck 2012 User Manual
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Trouble Shooting
Warnings
Basic Diagnostics
Repairs
Maintenance
Wiring Diagram
LPEFI
General Diagnostic Manual
2012 Isuzu NPR Trucks with 6.0 Liter Engine
Mono-Rail System
(Trinity Industries Tank Design)
October, 2012
Manual # M4-121-Isuzu
Bi-Phase Technologies, LLC
Eagan, Minnesota, U.S.A.
This manual is for general diagnosis that applies to any LPEFI
system installed on any
vehicle. Where there is a difference in components or installation, it will be identified by
specific vehicle. The theory and diagnostics for the system are the same for any vehicle
that the system might be installed on. However, the system is calibrated to a specific
vehicle and some components, specifically injectors, cannot be interchanged.
In this manual you will find different approaches to diagnostics and troubleshooting. We
will reference specific OEM repair manuals where a technician may need to obtain the
OEM manual to complete the diagnostics. In many cases, the propane injection system
may not be the fault and further investigation of the engine control system may be
required. Remember the basics when troubleshooting. To prevent the replacement of
good components it is necessary to have a general knowledge of both the LPEFI
system
and the vehicle.
“Read all instructions before use to avoid injury”
Anyone who performs repairs to the LPEFI
system must be trained and
certified. This is a propane system and anyone who performs repairs must
have knowledge of Liquefied Petroleum Gases and understand safe
handling and characteristics of such. Some states may require a license to
work on propane vehicles. Consult your state or local authorities or your
state propane gas association. Bi-Phase Technologies is not responsible
for your oversight to comply with federal, state or local laws regulating
the installation or repair of propane gas systems.
The LPEFI
system is a sequential multi-port fuel injection system that injects propane in
a liquid state to the engine. It works the same way as a modern sequential multi-port
gasoline fuel injection system and can be diagnosed with the same diagnostic scanners
used for gasoline vehicles.
The LPEFI system is covered by U.S. and International patents. The LPEFI
system is
also certified to the United States E.P.A. standards.
The information in this manual is believed to be accurate as of its date of publication but
it is subject to change. Up-to-date information and changes, if any, can be requested
from Bi-Phase Technologies.
In the event of any safety-related changes, Bi-Phase Technologies will notify all
customers who returned the warranty registration card for the affected vehicles.
1
2
TABLE OF CONTENTS
PropaneSafetyWarnings...................................................................................................................4‐5
FactsaboutPropane&PropanePoweredVehicles................................................................................6
ApproximatePropertiesofLPGases......................................................................................................7
Theory&Operation...........................................................................................................................8‐9
BasicDiagnostics............................................................................................................................10‐15
Checking&ReleasingFuelPressure..........................................................................................11‐12,21‐25
CheckingFuelLines.............................................................................................................................13‐14
CheckingFuelInjectors.......................................................................................................................14‐15
Electron
3SwitchBoxAmperageTestSpecifications..........................................................................................21
PressureTestingtheLPEFI
LPEFI
TroubleshootingbySymptom.........................................................................................................26‐33
icEn
gineManagement......................................................................................................16‐20
®
system(FlowChart)..............................................................................22‐24
®
PurgeLogic................................................................................................................................25
RepairProcedures..........................................................................................................................34‐53
Injectors..............................................................................................................................................35‐37
LPDM...................................................................................................................................................38‐44
FuelPump.............................................................................................................................................39
FuelLines...................................................................................................................................................45
TankControlBox(PurgeBox)...................................................................................................................46
Purgingthetank..................................................................................................................................47‐49
Drain/Evacuatingthetank..................................................................................................................50‐53
Mainte
SendingUnitValues............................................................................................................................55
WiringDiagram…………………………………………………………………………………………………………………………………60
Tank&HoseConfigurations...........................................................................................................61‐62
ServiceTools.......................................................................................................................................63
nance...............................................................................................................................
...54‐59
Bi‐PhaseTechnologies,LLC
Page left blank for notes
3
Bi-Phase Technologies
LPEFI Propane Safety
4
This is a safety alert symbol. It is used throughout this manual to alert you to
potential hazards. Whenever you see this symbol, you should read and obey the safety
warnings that follow. Failure to obey these warnings could result in serious personal
injury or property damage.
Warning: Never loosen fittings or vent any propane. Escaping
propane can cause frostbite and severe freeze burns. Wear
insulated PVC rubber gloves resistant to propane. Goggles
for protection against accidental release of pressurized
products and thermal protective clothing when handling
refrigerated liquids.
Propane is stored as a liquid. When you release liquid propane, it tries to evaporate as
quickly as it can, by absorbing heat from its surroundings. Everything it touches gets
chilled to -44 degrees F (-42 degrees C). If liquid propane sprays on your skin, it will
freeze it. Anyone who works with liquid propane must wear PVC insulated rubber
gloves.
Danger: Do not remove any valves, bulkheads, or fittings from a
tank unless the tank has been drained completely. The
pressure inside a propane tank can push a loosened
bulkhead or valve out with enough force to cause injury or
death.
Propane is stored under pressure. When you remove a valve or bulkhead from the tank, all
of the pressure is released at once in a violent rush. Always drain the tank before you work
on it. Failure to do this will result in damage to the tank or valves and can result in severe
injury or death. You should drain the tank by the fuel transfer method and/or by using a
flare stack in an approved safe manner. Your propane supplier can help you with this.
_______________________________________________________________________
Bi-Phase Technologies
LPEFI Propane Safety
_______________________________________________________________________
Warning: Keep all sources of ignition away from propane vehicles
while the fuel system is being serviced. Even if the tank
and fuel lines are empty, there may still be flammable
vapors near the vehicle.
Do not allow smoking, sparks, flames, recent or running vehicles or other sources of
ignition when fueling, servicing and vented propane. Failure to do this could result in
fire or explosion, causing severe property damage, injury or death.
_______________________________________________________________________
Warning: Do not disconnect any propane hoses unless they have been
properly drained completely.
Propane in the hoses is kept under pressure, even when the engine is off. When you
disconnect a hose; the internal pressure is released all at once. Always drain the fuel
lines before you disconnect them. Failure to do this can result in damage to the hose
fitting and possible injury. See repair procedures in this manual for instructions.
________________________________________________________________ _______
5
Danger: Do not vent or release propane indoors or near sewers, pits
or low lying areas. Propane can accumulate in low spots,
creating a fire hazard. Propane can also displace oxygen,
creating a suffocation hazard.
Propane is heavier than air. It can fill low, sheltered areas with flammable vapors. If
these vapors are ignited, they can create a fire or explosion, causing severe property
damage, injury or death. Never release propane near sewers, pits or indoors.
_______________________________________________________________________
Bi-Phase Technologies
LPEFI Facts about Propane & Propane Powered Vehicles
Propane gas is the most widely used alternative fuel, with nearly 4 million vehicles
worldwide running on propane. More than 350,000 vehicles run on propane in the U.S.
according to the U.S. Department of Energy’s Alternative Fuels Data Center.
Propane powered vehicles offer the best combination of durability, performance and
driving range.
The first propane powered vehicle ran in 1913.
Bi-Phase Technologies’ LPEFI
(Liquid Propane Electronic Fuel Injection) system has
surpassed other technologies today by introducing liquid fuel injection. This technology
improves power, efficiency and operating characteristics. For more information, call for
our General Information and Training Manual.
Safety comes first is a motto you should always live by. Without knowledge of a
product, it is hard to follow this motto. In our manuals we try to stress the need for
knowledge and provide warning signs to alert you.
It is your responsibility to know the law. National Fire Protection Association (NFPA)
has manuals to help you understand safe handling of many products. We recommend
that you obtain and read their NFPA #58, Standard for the Storage and Handling of
Liquefied Petroleum Gases.
A number of training programs and efforts have been implemented throughout the
country. The National Propane Gas Association has developed a Certified Employee
Training Program (CETP), which provides service personnel with a complete technical
training curriculum. We encourage you to contact your state propane gas association or
the National Propane Gas Association for more information on how you can benefit from
such programs. Visit www.propanesafety.com or www.npga.org for more information.
6
Bi-Phase Technologies
LPEFI Approximate Properties of LP Gases
(Commercial Propane)
C
3H8
Specific gravity of liquid (water = 1) at 60 degrees F. 0.504
Initial boiling point at 14.7 psia, in degrees F. - 44.0
Weight in pounds per gallon of liquid at 60 degrees F. 4.24
Cubic ft. of vapor per gallon at 60 degrees F. 36.38
Cubic ft. of vapor per pound at 60 degrees F. 8.66
Specific gravity of vapor (air = 1) at 60 degrees F. 1.50
Ignition temperature in air, in degrees F. 920 to 1120
Maximum flame temperature in air, in degrees F. 3,595
Limits of flammability in air
Percent of vapor in air/gas mixture
Lower 2.15
Upper 9.60
Air/Fuel ratio by volume 15.6:1
Air/Fuel ratio by weight 24:1
Octane number as it relates to gasoline 98 to 102
Heating values
BTU per cubic foot 2,488
BTU per pound 21,548
BTU per gallon 91,500
Chemical formula C
Vapor pressure in psig
70 degrees F 127
100 degrees F 196
105 degrees F 210
3H8
7
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Bi-Phase Technologies
PEF
Theor
& Operation
Introduction
This article covers basic description and operation of the LPEFI system. Read this information before
diagnosing vehicles or systems with which you are not completely familiar.
The LPEFI System
The LPEFI
system is a direct replacement propane fuel injection system. It replaces the gasoline fuel
injection system and works the same as a gasoline fuel injection system with the exception it injects
propane, in a liquid state, into the intake port. The gasoline system electronic engine management stays the
same and controls the LPEFI
system just as it did the gasoline injection system. Onboard diagnostics
remain unchanged so the same scan tool and diagnostic approach remains equal to a gasoline system. The
only change in electronic engine management is the fuel enrichment strategy on start up. Gasoline needs a
very rich fuel mixture to start the engine and differs greatly based on outside ambient temperatures. With
propane this fuel enrichment requirement is much less, thus reducing the level of start up emissions
compared with gasoline. The LPEFI
system accomplishes this start up fuel enrichment strategy by
recalibrating the PCM for propane fuel enrichment.
The LPEFI
system consists of three main components: the tank, the fuel lines and the injectors. The tank
is located to the rear or middle of the vehicle and the lines are routed forward to the engine compartment
where the injector rail assemblies are mounted in the same position as the original gasoline injector rails
were installed.
The Tank (ASME design, 312.5 p.s.i. working/design pressure)
The fuel tank is the most complicated area of the system. It includes an internal electric fuel pump & filter,
fuel supply & return valves, baffle that keeps the pump submerged in liquid propane and various other
valves, fuel level float assembly, pressure relief valve, overfill prevention device, and liquid service valve.
LPEFI
fuel delivery to the injectors and an optional tank, which only transfers fuel to the main fuel tank based on
fuel level inputs to a transfer module. The main fuel tank fuel pump increases or boosts the tank pressure
by 35 to 50 psi. No matter what the propane tank internal pressure is, the pump boost remains the same.
This is how the propane stays a liquid throughout the liquid supply section of the system. The fuel is
supplied to the injectors and whether the injector is open or not fuel passes through a cooling bushing in the
injector and is returned to the tank. This is called a refrigeration cycle and also aids in maintaining the fuel
in a liquid state throughout the supply passageways in the system. Because propane easily vaporizes, when
the refrigeration cycle stops (when the engine is turned off) or if the return valve malfunctions closed, the
propane will vaporize and cause a loss in power or hard hot restarting. To help in hot restarting, the system
goes through a purge cycle for 10 to 15 seconds before every start up attempt. This strategy is built into the
system’s electronic tank control box. See more about hot restart/hot soak in this manual.
vehicles may have one or two tanks. If it is fitted with two tanks, a main tank, which controls all
8
Bi-Phase Technologies
LPEFI Theory & Operation
The Fuel Lines
The fuel lines consist of two flexible hoses, one inside the other, in a concentric arrangement. The nylon
inner line supplies liquid propane to the injectors while the area between the outside of the inner line and
the larger outer hose is the fuel return passage.
The concentric fuel line design has a number of benefits:
1. Cuts the number of possible leak points in half,
2. Reduces vapor-lock in the supply line by using the return fuel passage as insulation,
3. Postpones the vapor-lock that occurs after a hot engine is shut off,
4. Shortens the purge cycle time needed to restart a hot engine.
The Injectors
The LPEFI
injectors that they replace. The injector electrical circuit resistance value is 13-15, similar to a gasoline
injector.
Each fuel injector has a supply passage and a return passage. The fuel injector rails have the same
concentric design as the fuel lines. The passage in the injector from the supply section to the return section
is restricted by a cooling bushing. As liquid propane passes through the cooling bushing, a pressure
reduction takes place, which causes the propane to vaporize and effectively cools the area around the
supply section. This is called a refrigeration cycle and aids in maintaining the fuel in a liquid state for all
driving conditions, regardless of the outside temperature.
The injector delivers propane in a liquid state into the intake port. It vaporizes immediately upon exiting
the injector. This rapidly expanding liquid cools the incoming air to the engine often resulting in a little
more horsepower than the gasoline system could achieve, not to mention the inherently improved exhaust
emissions that propane is known for.
system injectors are designed specifically for liquid propane. They mimic the gasoline fuel
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Bi-Phase Technologies
PEF
Basic Dia
nostics
All Models
Introduction
The following diagnostic steps may help prevent overlooking a simple problem. The first step in
diagnosing any drive-ability problem is verifying the customer’s complaint with a test drive under the
conditions the problem reportedly occurred.
Always perform a careful and complete visual inspection first. Most engine control problems result from
mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before
condemning the LPEFI
Visual Inspection
Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical
connectors fit tightly and are not corroded. Visually inspect for any loose or drop harness looms coming in
contact with the injector rails or components. Visually inspect all vacuum hoses and ensure they are
properly routed – not pinched, cut or disconnected. Visually inspect the secondary ignition wires, spark
plugs and ignition coils. Ignition weakness shows up much sooner on propane fueled engines than a
gasoline engine. Visually inspect each, injector insulator housing for cracks, cuts or o-ring sealing at the
manifold or at the top o-ring of the insulator housing (injector repair in this manual). Listen to the fuel
pump operation and the opening “click” of the fuel supply valve. Initiate a purge cycle by turning the
ignition key to the on position (purge logic chart in this manual).
Preliminary Checks
Check that the following systems and components are in good condition and operating properly before
diagnosing problems in the LPEFI
1. Battery condition
2. State of tune (ignition system)
3. All wiring and vacuum connections
4. Air cleaner and ducting
5. Cooling system
Mechanical Inspection
system, perform each test listed in this article.
fuel system.
Warning: DO NOT use the ignition switch during compression test on fuel injected
vehicles. Use a remote starter to crank the engine. Fuel injectors on many models are triggered by
the ignition during cranking mode, which can cause a flammable fuel mixture in the intake manifold
when performing a compression test.
Compression – Check engine mechanical condition with a compression gauge, vacuum gauge or an engine
analyzer. Compression pressures are considered within specifications if the lowest reading cylinder is
within 75 percent of the highest reading cylinder.
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Bi-Phase Technologies
PEF
Basic Dia
nostics
Mechanical Inspection, cont’d
Exhaust system back pressure – The exhaust system can be checked with a vacuum or pressure gauge.
Remove the O
exhaust back pressure is greater than 1¾ to 2 psi., the exhaust system or catalytic converter is plugged. If a
vacuum gauge is used, connect the vacuum gauge hose to an intake manifold port and start the engine.
Observe the vacuum gauge. Open the throttle part way and hold steady. If the vacuum gauge reading
slowly drops after stabilizing, the exhaust system should be checked for a restriction. Also, if the vacuum
gauge will not drop below 3” Hg on a wide open throttle condition or WOT loaded condition, check the
exhaust system for restriction. Leaks in the exhaust system, if upstream from an O
fuel control problems due to oxygen dilution in the exhaust, which causes inaccurate O
sensor and connect a 0-5 psi pressure gauge. Run the engine at 2500 RPMs and if the
2
sensor, can also cause
2
sensor response.
2
Fuel System
Engine does not crank – Check for hydrostatic lock (water or liquid in a cylinder). Repair as needed.
Check for starting and charging system problems.
Engine cranks but will not start
1. Check fuel tank contents and fuel gauge accuracy
2. Check ignition system for good secondary current at the spark plugs – if no spark exists or if spark
is weak, repair ignition system problem first
3. Check fuel lines and fittings for leaks – if no leaks are found, check fuel delivery system for
proper pressure; check for +12 volts to fuel delivery system
4. Check for defective fuel injector; a leaking fuel injector could cause a rich (flooded) condition and
cause a no-start; initiate a purge cycle and after the purge cycle is complete listen at the intake
manifold for injector leaks; open the throttle plate, smell and listen, pull the PCV valve and smell
and listen, lift the injector rail out of the manifold (without disconnecting fuel line) and visually
inspect
5. Check the ECT, coolant temperature sensor – confirm the ECT is in proper working condition
and; if the sensor is faulty
Warning: Always relieve fuel pressure before disconnecting any fuel injection related
component. DO NOT allow uncontrolled fuel release. Never loosen fittings or vent any
propane unless you are wearing insulated PVC rubber gloves; escaping liquid propane can
cause frostbite and severe freeze burns. Do not disconnect any propane hoses or remove any
injectors unless the fuel lines have been properly drained completely. Never release fuel
indoors or in an area where vapors could accumulate – source of ignition could ignite the air
fuel mixture and cause severe injury and property damage.
Fuel Pressure Release
To prevent the fuel pump and fuel supply valve from opening during repair, disconnect battery and/or
electronic tank control box – always disconnect negative battery terminal first.
1. Remove the fuel system Schrader Valve cap on the LPDM
2. The fuel pressure test gauge has a long drain hose; route the drain hose to a flare stack or other
receptacle for flammable propane vapor; never release propane indoors
3. Install the brass collar from the fuel pressure test gauge to the Schrader Valve, with the grooved
end facing out
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Bi-Phase Technologies
PEF
Basic Dia
nostics
Fuel Pressure Release, cont’d
4. Make sure the small thumb valve next to the gauge on the Bi-Phase gauge set is closed
5. Connect the test gauge to the collar; this connection will press the center pin on the Schrader
Valve releasing propane into the hose; this is a sensitive connection and must be confirmed; if the
pressure gauge does not react or reacts slowly, push in on this connection to confirm it has
penetrated the center pin of the Schrader Valve; the brass collar has some adjustments and may
also require oiling the o-ring occasionally
6. Open the valve near the pressure gauge to drain the propane through the long hose; note that the
Schrader Valve does not drain the tank – it only drains the main fuel line and the injectors
7. When the gauge reads “0” and there is no pressure exiting the end of the hose, you may disconnect
the fuel lines or injectors as needed (more detailed procedures and photos on page 36)
Warning: Do not remove the LPDM or any tank valves from the tank at this time.
Propane tank is under pressure. The procedure described previously only drains the fuel
lines for service. Serious injury or death could occur.
Fuel Pressure
Internal tank pressure must be established first. Use the 3-switch diagnostic box from Bi-Phase
Technologies, turn on the fuel supply valve rocker switch and push the fuel return valve “push” switch.
Hold down the fuel return valve switch for 30 seconds or until fuel pressure stabilizes. This is internal tank
pressure. When checking fuel pressures over a given time always recheck internal tank pressure due to
changes in ambient temperature.
When diagnosing the system it is very important to consider this information as it affects the accuracy of
your diagnosis. Boost Pressure = 35 to 50 p.s.i. (pressure over internal tank pressure)
Fuel pressure with return valve open (all models) – With the return valve open or during a purge cycle
the fuel pressure will be 5 to 15 psi below normal operating pressure (internal tank pressure plus boost
pressure). Should the pressure drop more than 15 psi. evacuate the fuel in the fuel lines (reference the
procedures in this manual), remove the primary hose and inspect the white nylon inner liquid supply line in
the primary hose at the LPDM. It could require that you visually inspect all hoses for proper inner liquid
supply line length.
Fuel pressure should always be confirmed first. If fuel pressure is not within specification the system will
malfunction. Fuel pressure can cause many types of drive ability complaints.
Bi-Phase Technologies
LPEFI Basic Diagnostics
13
Concentric Fuel Lines
As previously discussed, the fuel lines of the LPEFI
supply and fuel return to be accomplished inside one fuel hose. There are many benefits to this design as
mentioned in the theory section of this manual.
The sealing of the white nylon inner line to all the specific components of the system is very critical. If this
seal is lost, damaged or not made the vehicle will experience hard starting when hot, reduced power under
load, unbalanced injectors (rail to rail or bank to bank) and in extreme cases a no-start condition.
It is very difficult to install the lines and caution should be taken when assembling the concentric fuel lines
that connect from the LPDM and the injector rails. The inner lines are small and easily crimped (kinked)
during installation to the fuel rail. Also damage to the O ring seal in the rail may occur. It is recommended
to coat the metal hose end fitting and the white nylon inner line with clean motor oil before attempting
installation. If the white nylon inner line is crimped during installation or repair of the system a new hose
assembly must be obtained. The white nylon inner line is custom fit to each larger outer hose. Do not
assemble the hose with a crimped inner line; it will cause drive-ability problems. Years of process
development have caused the installation to be more difficult. However, at this time there is no other way
to rely on a proper fit and reliability.
Each white nylon inner line is sealed by a single o-ring located below the inner line alignment bushing
(finger bushing). This is found in each hose port whether it is the LPDM, or the injector rail end fitting.
See illustration below.
system are a concentric design. They permit fuel
Injector rail end fitting & hose
utilizing quick disconnect
much like gasoline
Bi-Phase Technologies
LPEFI Basic Diagnostics
Fuel Injectors
Fuel Injector check
1. Connect a tachometer to the engine; run the engine at idle; disconnect and reconnect injectors
individually (this may also be accomplished with a scan tool); if each injector causes a momentary
drop in engine speed of at least 100 RPMs, injectors are giving proper fuel delivery; RPM drop
should only be momentary as the IAC (idle air control) will attempt to reestablish correct idle
RPM
2. Replace any injectors that do not cause sufficient drop in engine speed; when test is complete, turn
engine off; to check curb idle, refer to the emission control specification on the decal in the engine
compartment or the OEM service manual for the particular vehicle
3. With the system pressurized listen, smell, spray with leak detection fluid and visually inspect
injectors for fuel leaks from the injector tip and housing; open the throttle plate to listen and smell,
or without disconnecting the fuel lines lift the injector rail out of the intake manifold to visually
verify that no injector leaks fuel; if an injector sprays fuel or leaks externally without an electrical
demand, the injector must be replaced
4. The fuel injector housing is a heat insulator and is installed over the injector itself, even though it
may look as one piece; the injector insulator housing is sealed onto the injector with one or two
o-rings, depending on the design revision level of the injector; the early single o-ring sealed
injector housing may lose its seal causing a vacuum leak; an injector should hold a vacuum if
checked from the bottom of the housing with a hand operated vacuum pump (reference injector
repair in this manual)
5. The fuel injectors are calibrated for each specific engine; injectors are also assembled on each rail
within a specific range of flow; if an injector from a different engine family is installed it could
cause an out-of-balance situation and set a diagnostic trouble code in the PCM
Fuel injector circuit – Disconnect all injector harness connectors. Use a digital ohmmeter to check
resistance across the terminals of each injector. The nominal resistance for each injector is 12.6 to 13.8Ω.
An acceptable range is 12Ω to 15Ω, but not to exceed 2Ω between the lowest reading injector to the highest
reading injector. If there is greater than 2Ω difference, choose and replace the highest or lowest resistance
injector, whichever corresponds, to achieve a range inside 2Ω. If the resistance test proves an open circuit
the injector must be replaced. Refer to the OEM service manual and wiring diagram for more information
if the wiring harness is at fault.
Ignition Checks
(Note: On many newer vehicles if an ignition failure occurs, the ignition system may continue to operate
with limited ability. Diagnostic trouble codes should be present if this occurs and the engine may be hard
to start. The ignition timing will also be fixed or no change in timing with RPM or load changes.)
Initial Inspection
1. Visually inspect ignition system components and wiring for evidence of damage or loose
connections; check condition of spark plugs, spark plug wires and distributor cap and rotor (if
equipped); repair or replace damaged components
2. Ensure idle speed and ignition timing is correct; check all components that could affect ignition
timing; refer to OEM specifications
Crankshaft position sensor
Camshaft position sensor and/or sensor timing
Crankshaft end play
Timing belt or timing chain condition, worn timing gears, chain or belt can cause erratic
timing
MAP or MAF sensor signals
For more detailed information refer to the OEM repair manual
3. Ensure spark plug wires are properly connected and routed in correct firing order
14
Bi-Phase Technologies
LPEFI Basic Diagnostics
Ignition Checks, cont’d
4. Check for spark – Disconnect a spark plug wire from a spark plug; connect a spark plug tester
between the spark plug wire and ground; crank engine and check for a strong consistent spark;
repeat test for each spark plug wire; if no spark is present check ignition coil primary wiring, coil
output or refer to OEM repair manual; if spark appears to be inconsistent do the same as
previously mentioned, but confirm the condition of the spark plug wire and repeat test; an ignition
scope analyzer is also recommended for checking ignition condition; an approved spark plug tester
must be used to prevent damage to ignition control components
5. Using a digital ohmmeter check the resistance of each spark plug wire; high tension wire
resistance should be 4000 to 7000Ω per foot; replace as necessary
6. Check power to coil – Disconnect primary wiring to coil/coils; turn on ignition and measure
voltage of primary positive voltage wire to coil connector; if less than 10 volts repair battery
condition or primary positive voltage wire
7. Check coil/coils – Disconnect coil, using a digital ohmmeter measure resistance of ignition coil
between primary wire terminals; measure resistance between ignition coil’s secondary terminals
and positive primary terminal; refer to appropriate OEM repair manual for exact resistance values
15
Bi-Phase Technologies
LPEFI Electronic Engine Management
16
Introduction
The LPEFI
engines. The design intent was to allow direct replacement of the gasoline fuel system to the LPEFI
system was developed and designed for use on modern sequential fuel injected gasoline
system with no change in the original gasoline electronic engine control strategy or onboard diagnostics.
With this said, it is very important that a technician understands electronic engine management theory. In
this section we will not attempt to write the book on electronic engine control or self-diagnostics, but
briefly explain some theory and operation of the general idea of electronic engine management and some
areas that will help in the diagnosis of the LPEFI
system. For details on specific vehicles you should refer
to the OEM repair manuals.
Electronic Engine Management
Power-train control module – The PCM monitors engine operating conditions by input received from
engine sensors. Control output actuators supply the function of fuel supply, incoming air, timing, ignition,
EGR, evaporative emission control to provide the demanded operating condition the driver or the PCM
desires based on the inputs from the engine sensors. The implementation of electronic engine management
brought many benefits:
1. Improved exhaust emissions,
2. Improved power,
3. Improved fuel economy,
4. Improved durability & reliability, and
5. On-board self diagnostics.
Since the first generations of electronic engine management, about 1980, many improvements have been
made. Today all vehicle manufacturers comply with the standards of OBD II (on-board diagnostics second
generation). OBD II did drastically change the way electronic engine management is carried out but it did
not change the original input versus output control strategy. It did require that the names for sensors and
actuators used are common from manufacturer to manufacturer, the same data link connector be used and a
generic list of trouble codes and data are retrievable by aftermarket diagnostic scan tools. In addition, more
monitors were added to track degradation of emission control components and warning flags that would
turn on the malfunction indicator lamp for things like cylinder misfire or catalytic converter failure.
Manufacturers began implementation of OBD II as early as 1994 on select vehicles with a goal to be
completed with light duty trucks by 1996. Today, they are still adding to it and implementing it on heavier
vehicles.
The engine control system consists of the PCM, relays, modules, sensors, switches and actuators. The
PCM sends out electrical reference signals to engine sensors and then analyzes the return signals. The
engine sensors supply specific information to the PCM, in the form of electrical signals, to determine
engine operating conditions.
In the event of a sensor or actuator failure, the PCM initiates an alternative strategy or failure mode to
allow the vehicle to maintain drive ability. In the event of PCM failure a limited operating strategy will be
activated. This provides minimal engine operation and any self-test or feedback systems will stop. The
malfunction indicator lamp will come on and stay on until the vehicle is repaired or until the PCM has
determined that all signals have returned within operating limits and then the PCM will resume normal
operation.
Vehicles are equipped with different combinations of input devices. Not all devices are used on all models.
To determine the input devices used on a specific model refer to the appropriate OEM repair manual and
wiring diagrams.
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Electronic Engine Management, cont’d
Some common input devices
Crankshaft position sensor
Camshaft position sensor
Engine coolant temperature sensor
Inlet air temperature sensor
Oxygen sensor
Throttle position sensor
Mass air flow sensor
Manifold absolute pressure sensor
Vehicle speed sensor
EGR position sensor
Knock sensor
Output signals are signals that send a demand to an actuator; some common actuators
Fuel injectors
Fuel pump
Idle air control or idle speed control
EGR control
Canister purge control solenoid
Spark control
MIL (malfunction indicator lamp)
Transmission controls
There are many more inputs and outputs, these are some common ones. Vehicles are equipped with
different combinations of computer-controlled components. Not all vehicles are equipped with the same
components. Always refer to the specific OEM repair manuals and information.
Self-Diagnostics
With the capability to see data through the use of a scan tool and to verify areas of trouble by checking for
diagnostic trouble codes, today’s electronics have given us more ways to verify where and what the
problem might be. Each vehicle manufacturer has written steps in troubleshooting a vehicle. If the scan
tool leads you to a specific trouble area refer to the OEM written test to troubleshoot accurately. Some
aftermarket manuals are very good in diagnosing electronic engine controls.
To prevent the replacement of good components and wasting precious time, verify engine condition and
basic tune-up requirements before condemning electronic engine control components. If your scan tool
immediately warns of a bad sensor, check it first but remember that an out-of-tune engine or an engine with
internal mechanical deficiencies can trigger diagnostic trouble codes.
DTCs, diagnostic trouble codes, are generated when there is a gross error with a sensor signal, input or
output signal or the PCM can no longer control something, meaning fuel mixture, timing, EGR, canister
purge and so on. Many times a DTC is generated but the fault is not necessarily the same as the DTC. For
example, a vacuum leak may cause an oxygen sensor activity code or a fuel control code. In this situation
the vacuum leak is the problem but it affected the electronic control of fuel which could cause you to
replace an injector if you did not check thoroughly or even the replacement of an oxygen sensor.
Always remember the basics and eliminate all the easy things first.
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Self-Diagnostics, cont’d
Retrieving DTCs, diagnostic trouble codes, is always a good place to start when trouble shooting a
problem. If there are multiple DTCs, you need to evaluate them and troubleshoot with the first DTC listed.
Write down all the DTCs listed and investigate what each one stands for. Open up the data information
available and investigate the area of concern established by the DTCs listed. See if there is any correlation
between the DTC and the data associated with it. Many times you may find that the data reveals proper
function and there is no reason for generating a DTC. If this is the case, look at the freeze frame data, if
available, and see under what conditions the DTC was generated. This will help in diagnosing the problem.
The data information is very helpful. First, you can look at sensor and actuator activity live. This is very
effective diagnostics. Today, it is very important that a technician knows and understands on-board
diagnostics. It can save time and money, which benefits both the technician and the customer.
When diagnosing the LPEFI
stream.
ECT (engine coolant temperature)
IAT (intake air temperature)
IAC (idle air control)
STFT B1 and B2 (short term fuel trim bank 1 and bank 2)
LTFT B1 and B2 (long term fuel trim bank 1 and bank 2)
PW B1 and B2 (average injector pulse width bank 1 and bank 2)
02S11 (oxygen sensor bank 1 front sensor)
02S21 (oxygen sensor bank 2 front sensor)
It is very important that you know the meaning of the PID (parameter identification) names in the data
stream and understand the values displayed. In this manual we will only talk about a few of these terms.
Refer to OEM repair manual for a more detailed explanation. Many of the PID addresses are easy to
identify but some of the acronyms are confusing, and having an OEM repair manual or Mitchell manual is
very helpful. The more you work with electronic diagnostics the more familiar you will become.
Important PIDs, Explanation
ECT (engine coolant temperature) – The data is displayed as degrees F or C depending on your selection
for English or metric display. Engine coolant temperature is important because the learning function of the
computer does not begin until the engine reaches a programmed temperature. This temperature may vary
depending on vehicle model. For example a Ford may not begin to learn until the temperature reaches 165
degrees F. Always perform final diagnosis when the engine is at full operating temperature.
IAT (intake air temperature) – The data is displayed as degrees F or C depending on your selection for
English or metric display.
IAC (idle air control) – The data is displayed in % or counts. % is the percent of time it is on, 50% would
be half open or 75% would ¾ open. Counts would be the same, the higher the count the more open the
valve is. This could be important when a vacuum leak is suspected. Always refer to the OEM repair
manual for the operating range as each model varies.
STFT B1 or B2 (short term fuel trim) – This is displayed either in positive or negative percentages (%) or
in counts. Short term fuel trim is adjustments to fuel delivery, as it is happening at the moment you look at
it. The closer to 0% or 128 counts the better the fuel control is. A negative percentage indicates a rich
condition and the fuel control is subtracting fuel or adjusting the fuel delivery leaner while a positive
percentage is a lean condition and fuel control is adding fuel or adjusting the fuel delivery richer.
system, there are some PID values you may want to look at from the data
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Important PIDs, Explanation
STFT B1 or B2, cont’d
If it is displayed in counts the range for counts is 0 to 255. The middle of the range is 128 and any reading
less than 128 is a rich condition while any reading greater than 128 is a lean condition. This does not mean
the engine is running rich or lean, but means that fuel delivery is rich/lean and fuel control is adjusting from
that point to optimize fuel delivery for emissions, economy and drive ability. If the range of control
reaches the limit, lean or rich, then the engine is running lean or rich and the computer can no longer
control the fuel mixture and a DTC will be logged in the computer’s memory. If the computer recognizes
this in a second drive cycle it will illuminate the MIL, (malfunction indicator lamp or check engine light).
The STFT has a back up to extend its range of control. It is called LTFT, long term fuel trim, and if the
STFT is controlling too far to the lean or rich side of the middle of the range of control, the LTFT will learn
and allow the STFT to control closer to the middle of the range. This allows the STFT to have a much
longer time period of control. This allows the degradation of the air filter, the fuel filter, fuel injectors,
engine oil contamination, PCV, fuel pump and anything that can affect fuel and air delivery. For example,
when a very dirty air filter is replaced the fuel control will readjust over time or the same with a fuel filter
or the same after an injector is replaced.
LTFT (long term fuel trim) – This is displayed in either positive or negative percentages (%) or in counts.
It is also shown for bank one and bank two. Long term fuel trim is adjustments to fuel delivery over time.
The closer to 0% or 128 counts the better the fuel control is. A negative percentage indicates a rich
condition and the fuel control is subtracting fuel or adjusting the fuel delivery leaner, while a positive
percentage is a lean condition and fuel control is adding fuel or adjusting the fuel delivery richer. If it is
displayed in counts the range for counts is 0 to 255. The middle of the range is 128 and any reading less
than 128 is a rich condition while any reading greater than 128 is a lean condition. This does not mean the
engine is running rich or lean, but means that fuel delivery is rich/lean and fuel control is adjusting from
that point to optimize fuel delivery for emissions, economy and drive ability. If the range of control
reaches the limit, lean or rich, then the engine is running lean or rich and the computer can no longer
control the fuel mixture and a DTC will be logged in the computer’s memory. If the computer recognizes
this in a second drive cycle it will illuminate the MIL, (malfunction indicator lamp or check engine light).
LTFT levels adjust over time as previously mentioned and causes or allows the STFT to maintain control
closer to the middle of the control range. This allows rapid changes to fuel control for better response and
performance. The LTFT is like a fine-tuning function. This gives the STFT a much longer time period of
control. This allows the degradation of the air filter, the fuel filter, fuel injectors, engine oil contamination,
PCV, fuel pump and anything that can affect fuel and air delivery. For example, when a very dirty air filter
is replaced, the fuel control will readjust over time or the same with a fuel filter or the same after an
injector is replaced. If the battery is changed or disconnected it will reset fuel trim and a learning process
could take a few hundred miles. However, for diagnosis purposes bringing the vehicle to full operating
temperature and a short drive will give you an idea of where the controls stabilize. Anytime the STFT
values are stabilized close to the middle of the range of control the LTFT values should be accurate. If the
air filter is clean, the engine oil is not contaminated and the engine condition is good the LTFT values are a
good indicator of how well the injectors are calibrated. It is also helpful to review the LTFT values at
different load conditions, such as cruising at 45 mph or at a wide open throttle situation. If power seems
low and wide open throttle values are very lean this would give you something to look for.
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