Direct Injection In-Depth
In this section we will examine the fuel, ignition, electrical, and lubrication systems of Evinrude Direct Injection outboards.
Topics include:
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Component identification
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Operation of the fuel system and injectors
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An introduction to the Engine Management system
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Trouble shooting with the diagnostic software.
This module will focus on 2002 through 2006 evinrude Direct Injection or DI models. Some of them are labeled Ficht Fuel Injetion or Ficht Ram Injection
Some of the general principles we´ll discuss also apply to Evinrude and Johnson Ficht models made between 1997 and 2001, but there are significant differences. As always refer to the correct service manual for the model you are working on.
We will not be covering Evinrude E-TEC models in this section. Evinrude E-TEC models are advanced-technology, direct-injection two-strokes.
However, we need to differentiate E-TEC models from the earlier direct-injection models we are covering.
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DI models have a computerized system that monitors and controls all engine functions. The EMM is the heart of the engine management system; it adapts the engine´s performance to match its operating enviornment.
Sensors provide information to the EMM for throttle position; crankshaft position; engine RPM; ambient air temperature; engine temperature; atmospheric pressure; exhaust back pressure; lubrication; shift loads; system voltages; and to detect water in the fuel. The EMM uses this data to calculate the proper injection timing; injection duration; spark timing; spark duration and engine oiling.
This enhances fuel economy, reduces emissions and delivers optimum performance and smoother running at all throttle settings.
The throttle Position Sensor is a rotary potentiometer. This means it is a variable resistor that is operated mechanically. It has three leads. One lead recieves a 5 volt reference voltage from the EMM As current flows through resistance, its voltage decreases. When the throttle is closed, the wiper is near the ground. So the voltage signal returned to the EMM is quite low. As the throttle opens, the wiper is moved closer to the source. The current reaching the wiper has gone through less resistance, so the voltage is higher.
The flywheel has encoder ribs cast in a specific pattern. Every time a rib passes the Crankshaft Position Sensor, it generates an AC signal. The EMM uses this signal to determine crankshaft position and RPM.
The Crankshaft Position Sensor is located at the top of the engine, next to the flywheel; its appearance and location varies among different models.
The air temperature sensor is a negative temperature coefficient thermistor. This means it is a variable resistor; and as temperature increases, resistance decreases. The EMM uses this sensor to determine the temperature of the air being pulled into the powerhead. It is attached to the intake air silencer. The EMM uses a 5 volt reference signal. This signal flows through the sensor to ground. The EMM measures the voltage at a point between a resistor inside the EMM, and the sensor.
As the temperature rises and the resistance decreases, more current flows to the ground. This decreases the voltage on the signal lead. The EMM equates the voltage with a temperature value. As the voltage decreased, the EMM knows the temperature is increasing.
Two devices inform the EMM of engine temperature. The water temperature sensor provides the EMM with the data for engine temperature. It is located in the port cylinder head. The water temperature sensor is a thermistor; it works the same way as the air temperature sensor. Again, we have the normal range. As temperature increases, resistance and voltage decrease.
When the voltage reading indicates a temperature high enough to damage the powerhead, the EMM will initiate S.L.O.W. and store a fault code. The water temperature switch is an on/off switch , not a thermistor. It is located in the starboard cylinder head. When the circuit grounds, the EMM initiates S.L.O.W. and stores a fault code.
When the keyswitch is turned on, an internal sensor in the EMM measures barometric pressure before the starter motor begins to crank. The EMM uses this data to compensate for changes in altitude and air density. When the engine is running, this sensor becomes the Exhaust Back Pressure Sensor. This EMM uses its data to adjust the fuel and ignition strategies for various load conditions. This sensor is connected by a hose to the exhaust passage.
A diaphram in the hose protects the sensor. The oil pressure switch is normally open; it closes at a preset pressure. The EMM monitors the switch , looking for a pressure spike after each firing of the oil injector. If the EMM does not detect a pressure spike, it rapidly cycles the oil injector. If the EMM still does not detect a pressure spike, it will initiate S.L.O.W. and store a fault code. The shift interruptor Switch is normally open. When the load on the shift linkage is high, the switch closes. This grounds a sensor circuit from the EMM. When this happens, the EMM shuts off fuel and spark to three cylinders, which reduces drivetrain loads to ease shifting.
The EMM -monitors alternator and battery voltage readings. These sensors are inside the EMM and are not serviceable. The water in Fuel sensor receives current from the EMM. If approximately 3/8¨ of water is present, the sensor completes a path to ground. The EMM turns on the ´Check Engine¨light and stores a fault code. |
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The EMM also monitors the engine for any operating problems, and alerts the operator through the System Check gauge.
During stratified combustion, a small cone of fuel is injected into the cylinder under high pressure, when the piston is near the top of its stroke. The high pressure causes the fuel to atomize as it leaves the injector, and mix with the air around the spark plug. The high pressure causes the fuel to atomize as it leaves the injector, and mix with the air around the spark plug. The EMM fires the spark plug repeatedly, beginning before the fuel arrives at the spark plug, and lasting through the combustion event. In the homogenous mode, fuel is sprayed into the cylinder much earlier, allowing a complete mixing of fuel and air in the combustion chamber. This complete mixing at higher engine speeds allows the engine to achieve maximum horsepower, while consuming considerably less fuel than a carbureted 2-stroke model. The EMM smoothly transitions between these modes, one cylinder at a time, by manipulating fuel spray injection and ignition timing.
This creates a smooth transition from low to high speed. Lubrication: DI models use a unique lubrication system. An oil pump, driven by crankcase pulses, supplies oil under pressure to an oil injector, a modified version of the fuel injector. From there, an oil manifold delivers the oil through lines to each cylinder, where it is injected through a hole in the cylinder wall. The EMM controls oiling by monitoring throttle position and engine speed to determine the engine´s load. It then calculates how often to activate the oil injector to provide proper lubrication. This injects a precise amount of oil to each cylinder.
Because DI models do not pass fuel through the crankcase, the fuel does not wash the oil off the This means the engine consumes significantly less oil, while still safely lubricating all internal parts. In addition to lubricating the cylinders and bearings, the lubrication system adds a small amount of oil to the fuel system, to reduce carbon buildup on the fuel injector nozzles. BRP recommends using XD100 oil for DI models. Its synthetic formula burns cleaner and provides superior lubrication.
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Computer software greatly simplifies DI diagnostics. The program does much more that the scan tools used to service other injection systems. Using a laptop computer and the Evinrude Diagnostic Software, the technician is guided through the troubleshooting procedure. The first versions of the Diagnostics Software ran on a hand-held Personal Digital Assistant, or PDA. If your shop still has working PDAs, you can use them to diagnose and service DI models. However, the PDA software is no longer supported by BPR. We recommend using the latest laptop-based software because it´s easier to use and offers more features.
Locate the diagnostic connector on the engine. Remove the cover and install the Diagnostic Interface Cable.
Attach the 9-pin connector to the computer´s serial port. Turn on the keyswitch , but do not start the engine for now. Launch the diagnostic program. Click Connect. When the computer has established communication with the engine, the program will indicate Online. The software allows you to view the engine´s status to see if anything is wrong. Any fault codes are displayed, along with an explanation of the fault. Fault codes are divided into three categories. Hard faults indicate problems that exist right here and now.
Faults that occur when the engine is running become Stored faults. It records when these faults happened, and saves them until they are cleared. Looking at Stored faults can help you see intermittent problems. Remember, fault codes are stored only when the engine is running; you will not set a Stored fault by performing diagnostic tests when the engine is not running. The persistent Fault tab lists all fault codes that have been stored even if they have been cleared; this may be useful for troubleshooting. By using the fault codes and the service manual, you can troubleshoot and test engine functions, and quickly isolate the problem. This can save a lot of time in completing the repair and getting your customer back on the water. Using the software, you can perform static tests such as firing fuel injectors, the oil injector, or ignition coils, one at a time.
You can also perform dynamic tests while the engine is running, selectively dropping a cyllinder to help isolate problems, or increasing or reducing fuel flow to one or all injectors. You can monitor all engine-mounted switches and sensors- check electrical system voltages--and examine the timing and pulse duration of both the fuel injector and spark. If you´re working with a 2002 or later DI model, you may notice an orange Oil Fault box on the Monitor screen.
This is because these engines use a diffrent method to monitor oil deliver; they dont supply the input the software is looking for. You can ignore this box. If there's a lubrication failure , the Active Faults box will turn red, and the engine will enter the S.L.O.W. mode. The diagnostics software must be used to perform certain service procedures, such as changing an injector or restarting the break-in mode for a rebuilt powerhead. The software has other features that make it a valuable tool. You can call up an RPM profile to examine how the engine has been used. You can also print out an engine report that includes all the information available through the software: engine model, and serial number, operating hours, fault codes, RPM profile, and more. You should always have an engine report ready before calling BRP Technical Service. Evinrude Diagnostic Software is a powerful troubleshooting tool that makes the technician´s job much is easier and faster.
Test Your knowledge!
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Therefore, in this program anytime we mention DI, we are talking about pre-E-Tech models.
E-TEC and DI are easy to tell apart because their injections look different and E-TEC models have a three-dimensional break line on the motor covers.
Direct Injection was the greatest two-stroke innovation since the invention of the outboard.
As we saw in module 3, conventional two-stroke outboards must get rid of exhaust and bring in a fresh charge of fuel and air every time the piston is down. As a result, the intake and exhaust ports are open at the same time, and some of the incoming air/fuel mix escapes through the exhaust ports without ever being burned.
Direct Injection in a Two Stroke
Direct Injection solves this problem by distributing the fuel after all the ports are closed. This prevents raw fuel from escaping, which reduces hydrocarbon emissions by up to 88 perccent, and increases fuel econmy as much as 35 percent.
Because of this, DI models offer the performance, light weight, and quick throttle response of a two-stroke.
They also offer fuel economy and emissions equal to or better than a four-stroke outboard. The heart of the DI system is the fuel Injector -- a combination high-pressure pump and injector nozzle.
Fuel Injector mounted on a cylinder head
The injector is mounted directly on the cylinder head, eliminating the high-pressure lines used by most injection systems. This simplifies the fuel distribution system, resulting in a smoother, quieter, more reliable outboard.
How it all works:
Injector Coil Assembly
The injector coil assembly is a powerful electromagnet. Just before a cylinder is ready to fire, the Engine Management Module, or EMM, switches on the injector coil assembly. This creates a strong magnetic field in the housing.
The magnetic force rapidly moves the injector armature towards the nozzle. The armature is hollow and moves easily through the fuel until it contacts the ball valve.
Fuel Injection Pulse Caused by Magnetic Field
As the ball valve seals, the armature begins to act as a piston, pressurizing the fuel in the injector nozzle. This pressure forces the poppet valve open, spraying fuel into the cylinder under high pressure. A spring returns the armature to its resting position, refilling the injector with fuel for the next firing
This high pressure has an important benefit: it atomizes the fuel into fine droplets, so it burns efficiently and completely. The amount of fuel delivered is determined by the duration of the electrical pulse. A longer pulse provides more fuel from the injector.
Lift Pump and Fuel Filter
DI models have a fuel handling system much different from carbureted models. A lift pump draws fuel from the boat tank, and pumps it to an engine-mounted fuel filter. This filter removes any debris in the fuel, and traps any water that might be present. A sensor in the filter alerts the EMM if water accumulates in the fliter.
Vapor Separator
The fuel then moves to the vapor separator, a water-cooled fuel reservoir that supplies fuel to the electric circulation pump. This pump distributes it to the fuel rails and injectors. Some of the fuel flows through the injector, which helps cool the coil assembly.
This warm fuel returns to the vapor separator, which contains a pressure regulator to maintain proper pressure in the fuel lines.
Water passages in the vapor separator cool the incoming fuel before it is pumped back to the injectors. Any excess vapor in the separator is vented to the intake manifold and burned.
Water Cooling the Vapor Separator