This is part two of this set.


The throttle body assembly is attached to the plenum and is used to control air flow into the engine. There are two 60 mm throttle plates that are progressively opened by the throttle cable. The Throttle Position Sensor is mounted under the throttle body and is used for Sensing throttle valve position. The Idle Air Control (IAC) valve is used to control idle speed and to prevent engine stalls due to changes in engine load.


The mechanical fuel pump (c) draws fuel from the boat's fuel tank (a) and through the water separating fuel fitter (b) (this filter is easily serviced with a spin on cartridge). The mechanical fuel pump will supply fuel to the Vapor Separator Tank.


This is a fuel reservoir mounted on the top of the engine, to the rear of the intake manifold. Fuel is pumped into this tank to supply the EFI system Electric Fuel Pump (e) which is mounted inside the VST tank. Fuel level is controlled by a float and needle and seat assembly (f). When the ignition switch is turned to the run position, the ECM will turn on the fuel pump relay for 2 seconds. When the ignition switch is turned to the crank position the ECM turns the fuel pump relay on causing the fuel pump to run. If the ECM does not receive ignition reference pulses (engine cranking or running), it shuts off the fuel pump relay, stopping the fuel pump. When the relay is activated the Electric Fuel Pump draws fuel from the tank, through a filter (0) mounted at the pump base. Fuel is then sent out of the tank outlet line under pressure and into the in-line Fuel Filter. IN-LINE FUEL FILTER (H)

After the fuel is pumped from the Vapor Separator Tank (VST) it passes through a fine-mesh, in-line fuel filter to trap any particles that may harm the fuel injectors. Note: Most fuel contaminants are trapped inside the water separating fuel filter, the in-line filter traps contaminants typically created by wear of the electric fuel pump and service is not often required.

Fuel is routed into the Fuel Rail through high pressure lines.


Fuel then enters the Fuel Rail Assembly which is located on top of the intake manifold. The Fuel Rail positions the fuel injectors in the intake manifold and supplies fuel evenly to each injector.


The fuel injectors are eight electric solenoid operated devices that meter pressurized fuel to each engine cylinder. The Fuel injectors are controlled by the Electronic Control Module (ECM) which grounds the injector coil to open the injector nozzle and allow fuel to spray into the intake manifold next to the intake valve. Fuel pressure to the injectors is controlled by the Fuel pressure Regulator


The Fuel Pressure Regulator is located at the forward end of the Fuel Rail. It is a diaphragm-operated relief valve that maintains constant pressure differential across the injectors at all times. An intake manifold Vacuum line is attached to the regulator housing and a spring is mounted inside the housing-pushing on the diaphragm. Engine manifold vacuum and the spring counteract each other to apply the correct pressure in the regulator diaphragm under all engine operating conditions. Fuel pressure is 34-38 PSI.


Fuel that is not used by the injectors is bled off and sent back to the Vapor Separator Tank (VST) through the Fuel Rail Return Passage.


The return fuel from the fuel rail enters the Vapor Separator Tank (VST). Fuel vapors are bled off by the Vapor Regulator Assembly and are sent to the intake manifold. This system avoids vapor locking and does not require a return fuel line to the boat's fuel tank.

Visual and physical inspection

The first step you should take is to make a careful visual and physical inspection of the system. A problem may be corrected without further checks and time can be saved. Check for vacuum hoses for correct routing, proper connections, pinches, kinks, cuts and splits. Some hoses are difficult to see. Inspect wiring for proper connections, pinches, cuts, burned or chafed spots or contact with sharp edges or hot exhaust manifolds. Check for air leaks at the throttle body, plenum or intake manifold. Inspect ignition wires for cracking, hardness and proper routing. Check that the proper size 12 Volt battery is being used and that it is fully charged. The EFI electrical system is very Voltage sensitive. A poorly charged battery can cause operating problems.


If nothing is found during the visual and physical inspection you should now make a Diagnostic Circuit Check. Note: Electronic components used in this system are often designed to carry very low voltage and are very susceptible to damage caused by electrostatic discharge. It is possible for less than 100 volts of static electricity to cause damage to some electronic components. It takes as much as 4,000 volts for a person to even feel the effects of a static discharge. Static charges are developed by friction and induction. Sliding across a seat can build up a charge of as much as 25,0000 volts. It is important to discharge yourself when testing and handling electronic components. Disconnect the negative battery cable before removing any electronic component. Never disconnect the battery while the engine is running. Make sure battery connections are clean and connected solidly. When charging the battery, disconnect it from the boat's electrical system.


To make the EFI Diagnostic Circuit Check turn the ignition switch off and hook up a Scan Tool or a Marine Diagnostic Code Tool to the Assembly Line Diagnostic Link (ALDL) Connector. You then follow the diagnostic chart in the service manual. This test sequence will let you know if the onboard diagnostics are working. If they aren't you will be directed to a test sequence to find the problem. If the on-board diagnostics are working you will continue through the test chart to find if any "trouble codes" are stored in the Electronic Control Module's (ECM) memory. The test tool will flash a code "12" three times after being switched to the "service" mode. If any "trouble codes" are present they will flash next for three times. If more than one "trouble code" is stored in the ECM memory the codes will be output tom the lowest to the highest-- each one flashing three times. After any "trouble codes" have flashed, a code'l2" will flash again, for three times, to let you know all codes have been displayed. If "trouble codes" are present you should refer to the proper ("Non-Scan" or "Scan") code chart, starting with the lowest code first, to diagnose the cause of the problem. If "trouble codes" are not present you should refer to the "Troubleshooting" section in the service manual for poor running engine conditions and items to check to isolate the problem. A scan tool may also be used to check for an intermittent problem while the engine is running. If no problem is found after working through the "troubleshooting" section, an out-of-range sensor may be suspected. To identify a sensor which is out of range, unplug it while the running the engine. After approximately two minutes, the diagnostic code for that sensor will set, illuminate the "Check Engine" light, and replace the sensed value with a default value. If at that point a noticeable performance increase is observed, the non-scan code chart for that particular sensor should be followed to correct the problem.

See part 1?

Go to wiring Diagram

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