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Discussion Starter #1
My 86 wing has a fuel system light that is on and it runs "ok" but at high rpms it misfires A suggestion was fuel pressure regulator. How do I go about testing the pressure?
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1985 GL1200 Limited Edition
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I'm not sure if there is a reed valve to check the pressure.. I'd start looking by tracing the fuel line from the fuel filter to the injectors.. The best I remember there is just the fuel line from the pump to the filter... You say the fuel system light is on? Have you checked for codes on the CFI computer under the trunk??

BTW, exactly how many RPM's are you turning before she starts backfiring??

And, That bike is a Looker!!!!!!!!! :oops::oops:
 

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A bad fuel pressure regulator happens about as often as the sun not coming up. Figure out the fuel system problem first.
 

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The fuel System light has nothing to do with the fuel system - it's the equivalent to a check engine light. Comes on when one of the sensors in the CFI system is out of spec or malfunctions. If the light is on, there is an error code. Start the bike, and look at the ECU for the error code. The ECU does not store these error codes, and as such, each time the ignition switch is turned off, the error code is lost. You mention a misfire at high RPMs, how high is this? Sounds like a faulty TPS.
 

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The fuel System light has nothing to do with the fuel system - it's the equivalent to a check engine light.
I was referring to the electrical part of the fuel system, not the fuel supply system, should have been more clear.
 

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I was referring to the electrical part of the fuel system, not the fuel supply system, should have been more clear.
Figured so. Had a similar issue a while back when I brought a second Limited Edition across Canada. Went over the fuel system with a fine tooth comb, and couldn't relate it back to the dash light. You're right about the pressure regulator, quite robust and will seldom fail. Nothing but a spring and diaphragm using differential pressure to regulate the fuel pressure.

There is a fuel injector manual for the CX500T that is quite good at explaining the CFI system - "Turbocharger/Computerized Fuel Injection Manual". Goes into a lot of detail about the various parts/pieces of the system. Bit different than the '85/'86 CFI system, but the basics are the same. The '85 and '86 FI systems are the third generation of the Honda PGMFI system on its bikes.
 

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02 GL1800 w/Auto Pilot
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There is a fuel injector manual for the CX500T that is quite good at explaining the CFI system - "Turbocharger/Computerized Fuel Injection Manual". Goes into a lot of detail about the various parts/pieces of the system. Bit different than the '85/'86 CFI system, but the basics are the same. The '85 and '86 FI systems are the third generation of the Honda PGMFI system on its bikes.
this one?


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That's the one.
 

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Discussion Starter #9
I'm new to this electrical stuff .How do I check the ECU? I usually get the misfiring at higher than 4500 rpm like downshifting and passing a truck when I need the power. Just running at high speed is no problem and 90 mph is smooth. Cold idle is rough and also stalling when stopped while cold.
 

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Do you have the service manuals for this bike. The OEM service manual, Electrical Troubleshooting manual, and the Supplement? Recommended and necessary tools to troubleshoot any issue with your bike.
 

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Discussion Starter #15
Do you have the service manuals for this bike. The OEM service manual, Electrical Troubleshooting manual, and the Supplement? Recommended and necessary tools to troubleshoot any issue with your bike.
I have a Clymer book and someone else sent me a website address for an online manual. Thanks.
 

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1985 GL1200 Limited Edition
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Just a thought: Have you or anyone else adjusted the Idle?? If the wrong adjustment screw was turned that'll throw the engine out of balance and can cause the Fuel light to come on and also produce some of the symptoms you've described!! There are two adjustment screws: one is under the CFI cover on the right rear of the engine and is for engine balance, NOT the idle!! Using a flashlight look across the rear of the engine while rolling the throttle with the engine off. You'll see a screw on the center of the throttle linkage. That's the Idle Screw!! Balancing the engine is fairly simple as you only have to balance the left and right sides, not front to back, needing two manometers not four...

Let us know what you find out!
 

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My experience is with the Throttle Position Sensor. There are indicator lights under the trunk on the ECM on the left side of the bike. It sounds like a TPS problem.

I replaced mine (again) a few weeks ago and made sure it was reading the correct voltage. She runs amazing now, cold and warm.

I haven’t been able to find an OEM TPS yet but the one I use is cheap and you’ll have to modify it.


 
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