Reading a lot of forum threads of late regarding 1985-1986 GW FI model issues. Fuel smell on first and even subsequent starts, blueish smoke on first start, low idle on first cold start, plug fouling, cylinder banks operating at different temperatures, and such.
The CFI system is a package deal that is designed and uses specific FI components that the ECU engine tune uses quite successfully to make these FI models operate quite well. The CFI system cannot be tweaked, or adjusted to accommodate any system issues, except that if a specific component fails or is starting to fail, a new/used component can be installed. Honda did not, nor does it want us to delve into the CFI system too much or too deep.
Terminology, there are no Pulse Generator (PG) sensors on the FI models. Completely different ignition system. The FI models have a crank sensor (Ns), and two camshaft sensors (GR/GL).
The TPS is used by the ECU to determine when the throttle plates are closed/open/opening. Very small calibration range to indicate this, 0.47 to 0.49 VDC. To calibrate the TPS, do not adjust the throttle plate stop screw. Can be done, but impacts on the engine tune. You calibrate the TPS by bringing the throttle plate lever to the throttle plate stop screw. Count the number of idle adjustment screw turns so you can return the idle back to where it needs to be.
The Ns crank sensor either works or it does not, same with the GR/GL sensors. The difference is that the engine will not start if the Ns sensor fails, the engine will operate with one camshaft sensor but not if both fail. If the Ns sensor is out of calibration, but has not failed, the ECU goes into a limp home mode.
The Pressure Balance (PB) sensors measure the manifold absolute pressure (MAP). The ECU will operate the engine with one sensor functioning, failure of both sensors and the ECU goes into a limp home mode.
If both fuel injectors on the same circuit fail, engine stops and will not start, and an ECU error code is generated. If one fuel injector fails, no error code is generated, but you start the process of looking for the cause of the misfire, engine not operating correctly.
The CFI system ECU does not monitor the fuel system even though the dash indicator for a CFI system fault is “FUEL SYSTEM”. This is Honda’s early FI “Check Engine” light.
The fuel system is a key element for the CFI system. The fuel system static pressure, engine stopped is approximately 36 PSI. The fuel system dynamic pressure, engine started and operating, is approximately 28 to 32 PSI. This pressure is regulated by the fuel pressure regulating (FPR) valve at the end of the fuel pressure rail.
Fuel pressure is important because it affects the amount of fuel being injected into the engine for a given power/RPM range. The fuel injectors have been reported as having a fuel flow rate of 280 cc/min at 43 PSI (3 BAR) fuel pressure. The fuel injectors are then derated for the CFI design operating parameters of approximately 30 PSI fuel system pressure. The fuel injector flow rate at approximately 30 PSI is 219 cc/min. These are large fuel injectors for a small horsepower engine, but as mentioned, the component data that the ECU uses to calculate the correct amount of fuel required for the best air-fuel mixture at any given engine power/RPM range has taken this into account.
Enough motherhood.
As I have mentioned, the CFI system is a well-designed, complex FI system that provides the best balance of components and FI system design to give you, the rider, a street motorcycle that performs very well for its intended purpose.
Fuel pressure affects the fuel pressure differential across the fuel injector, and can cause the engine to operate in a fuel lean or fuel rich condition.
Troubleshooting/maintaining this older FI system is not easy. Not much can be done. The ‘85/’86 GW FI models are the best compromise of system components and engine programming for the time.
If there are operating issues and you can identify the issues as being with the CFI system, it’s repair by replacement. If there are no issues indicated by the CFI system ECU, the issue may be with the CFI system, but it is time to look elsewhere.
Maintenance is a key element in the correct operation of the CFI system.
Fuel injectors need to be serviced. Having these cleaned, flow and leak tested is a good preventative maintenance routine. These are robust components but can fail. If you need a replacement injector, do as a set.
Try to get a set of fuel injectors of the same size. This is important because the ECU does not know what size the new fuel injectors are and will trigger these as if you still had the original fuel injectors installed. Smaller or larger fuel injectors will deliver different amounts of fuel to the engine based on the same ECU fuel calculations. You could, depending on how you ride your motorcycle, have a fuel lean or fuel rich condition because of the fuel injector change.
Make sure the fuel system pressures, static and dynamic are within specification.
Make sure the cylinder bank synchronization is as good as it can be.
Fuel pump has an inlet filter cone that needs to be inspected.
Ensure there are no vacuum leaks, regardless of size. First order of business.
Ensure the coils are within specification and the spark plugs wires and caps are in good condition.
Determine that the TPS is adjusted to specification.
Check the air inlet temperature and coolant temperature sensors.
The ECU can be starting to degrade/fail. Electronic parts only last so long. There are no servicing shops to address an ECU fault.
Once you have ensured that the CFI system and fuel system is operating correctly - no error codes, have to look elsewhere, but there is not much else to check.
This is a short overview of the CFI system and what you might want to consider doing. If you don’t identify or rectify the issue at hand, may not be able to in the long term. These are older motorcycles
The CFI system is a package deal that is designed and uses specific FI components that the ECU engine tune uses quite successfully to make these FI models operate quite well. The CFI system cannot be tweaked, or adjusted to accommodate any system issues, except that if a specific component fails or is starting to fail, a new/used component can be installed. Honda did not, nor does it want us to delve into the CFI system too much or too deep.
Terminology, there are no Pulse Generator (PG) sensors on the FI models. Completely different ignition system. The FI models have a crank sensor (Ns), and two camshaft sensors (GR/GL).
The TPS is used by the ECU to determine when the throttle plates are closed/open/opening. Very small calibration range to indicate this, 0.47 to 0.49 VDC. To calibrate the TPS, do not adjust the throttle plate stop screw. Can be done, but impacts on the engine tune. You calibrate the TPS by bringing the throttle plate lever to the throttle plate stop screw. Count the number of idle adjustment screw turns so you can return the idle back to where it needs to be.
The Ns crank sensor either works or it does not, same with the GR/GL sensors. The difference is that the engine will not start if the Ns sensor fails, the engine will operate with one camshaft sensor but not if both fail. If the Ns sensor is out of calibration, but has not failed, the ECU goes into a limp home mode.
The Pressure Balance (PB) sensors measure the manifold absolute pressure (MAP). The ECU will operate the engine with one sensor functioning, failure of both sensors and the ECU goes into a limp home mode.
If both fuel injectors on the same circuit fail, engine stops and will not start, and an ECU error code is generated. If one fuel injector fails, no error code is generated, but you start the process of looking for the cause of the misfire, engine not operating correctly.
The CFI system ECU does not monitor the fuel system even though the dash indicator for a CFI system fault is “FUEL SYSTEM”. This is Honda’s early FI “Check Engine” light.
The fuel system is a key element for the CFI system. The fuel system static pressure, engine stopped is approximately 36 PSI. The fuel system dynamic pressure, engine started and operating, is approximately 28 to 32 PSI. This pressure is regulated by the fuel pressure regulating (FPR) valve at the end of the fuel pressure rail.
Fuel pressure is important because it affects the amount of fuel being injected into the engine for a given power/RPM range. The fuel injectors have been reported as having a fuel flow rate of 280 cc/min at 43 PSI (3 BAR) fuel pressure. The fuel injectors are then derated for the CFI design operating parameters of approximately 30 PSI fuel system pressure. The fuel injector flow rate at approximately 30 PSI is 219 cc/min. These are large fuel injectors for a small horsepower engine, but as mentioned, the component data that the ECU uses to calculate the correct amount of fuel required for the best air-fuel mixture at any given engine power/RPM range has taken this into account.
Enough motherhood.
As I have mentioned, the CFI system is a well-designed, complex FI system that provides the best balance of components and FI system design to give you, the rider, a street motorcycle that performs very well for its intended purpose.
Fuel pressure affects the fuel pressure differential across the fuel injector, and can cause the engine to operate in a fuel lean or fuel rich condition.
Troubleshooting/maintaining this older FI system is not easy. Not much can be done. The ‘85/’86 GW FI models are the best compromise of system components and engine programming for the time.
If there are operating issues and you can identify the issues as being with the CFI system, it’s repair by replacement. If there are no issues indicated by the CFI system ECU, the issue may be with the CFI system, but it is time to look elsewhere.
Maintenance is a key element in the correct operation of the CFI system.
Fuel injectors need to be serviced. Having these cleaned, flow and leak tested is a good preventative maintenance routine. These are robust components but can fail. If you need a replacement injector, do as a set.
Try to get a set of fuel injectors of the same size. This is important because the ECU does not know what size the new fuel injectors are and will trigger these as if you still had the original fuel injectors installed. Smaller or larger fuel injectors will deliver different amounts of fuel to the engine based on the same ECU fuel calculations. You could, depending on how you ride your motorcycle, have a fuel lean or fuel rich condition because of the fuel injector change.
Make sure the fuel system pressures, static and dynamic are within specification.
Make sure the cylinder bank synchronization is as good as it can be.
Fuel pump has an inlet filter cone that needs to be inspected.
Ensure there are no vacuum leaks, regardless of size. First order of business.
Ensure the coils are within specification and the spark plugs wires and caps are in good condition.
Determine that the TPS is adjusted to specification.
Check the air inlet temperature and coolant temperature sensors.
The ECU can be starting to degrade/fail. Electronic parts only last so long. There are no servicing shops to address an ECU fault.
Once you have ensured that the CFI system and fuel system is operating correctly - no error codes, have to look elsewhere, but there is not much else to check.
This is a short overview of the CFI system and what you might want to consider doing. If you don’t identify or rectify the issue at hand, may not be able to in the long term. These are older motorcycles
