Injector problems - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 30 (permalink) Old 02-23-2020, 03:40 PM Thread Starter
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Injector problems

My #1 injector has constant power and ground.l, symptom was #1 cylinder flooding out and not building rpms. It seems they fire with a grounding pulse from the ECU. All my other injectors are working fine and power and ground are working as they should. I isolated the wire coming directly out of the ECU and it’s showing ground. So it’s got to be a sensor or the ECU itself. Question is what tells the ECU to fire?
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post #2 of 30 (permalink) Old 02-23-2020, 07:09 PM
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What year FJR are we looking at?
I may be mistaken but, in general terms the ECU pulses the ground to each injector, and the injectors are already powered. To keep it simple, firing should occur based on pulses from the ignition pickup on the right end of the crankshaft. Other sensors come into play of course, but not sure how any of that causes one injector to be constantly on.
I don't think any of us know the internal circuitry of the ECU..... have you done any recent work to the bike (e.g., valve check) that would affect any of these sensors or wires?

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post #3 of 30 (permalink) Old 02-24-2020, 05:16 AM Thread Starter
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Originally Posted by RaYzerman View Post
What year FJR are we looking at?
I may be mistaken but, in general terms the ECU pulses the ground to each injector, and the injectors are already powered. To keep it simple, firing should occur based on pulses from the ignition pickup on the right end of the crankshaft. Other sensors come into play of course, but not sure how any of that causes one injector to be constantly on.
I don't think any of us know the internal circuitry of the ECU..... have you done any recent work to the bike (e.g., valve check) that would affect any of these sensors or wires?

2003 that’s been sitting for quite a while. Had mice damage to the main harness, installed a new harness everything is working except that one injector. It has constant ground. Originally thought it was just clogged pulled and cleaned and no difference in performance, proceeded to check power and ground and it has constant ground which would open it. Bike idles and starts fine so I wouldn’t think the valves are out of spec, if they were it wouldn’t be enough to throw a sensor off. I will probably have to look at the wired that come off the sensors on the crank to make sure none are chewed. The sensors are on the right side of engine?
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post #4 of 30 (permalink) Old 02-24-2020, 07:26 AM
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I would disconnect the ECU and recheck the ground control wire from the ECU leading to the injector circuit in question. If the injector is no longer grounded then it would suggest the ECU is at fault, if the ground is still present it would suggest the wire leading to the injector is shorted to ground.
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post #5 of 30 (permalink) Old 02-24-2020, 08:13 AM
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The ignition pickup is behind the right side timing cover, the one with the large round access plug with the big screwdriver/coin slot in it. The wires travel up the forward side of it in a clip or two, then up under the throttle bodies to connect to the main harness. If there was a cut/chewed through/broken wire, the bike would not start. If pinched by removal/replacement of the timing cover, bike can run rather crappily since the ECU is not getting clean signals.
Other sensors... if coolant temp or cylinder identification sensor is unplugged/no circuit, bike will not start. ECU inteprets signals.... coolant temp will affect richness at cold, normal at hot. Intake air temp sensor (ambient air in airbox) will adjust mixture. Any corrosion/partly shorted wires/shorted can also affect what the ECU sees. MAP sensor detects vacuum and altitude, sends a voltage to the ECU.
I would unplug the ECU and replug just to refresh the connections since it's been sitting. Try manually moving the crankshaft (right timing cover, 14mm socket, rotate clockwise) say 90 degrees and see if the one injector still shows constant ground, i.e, ECU given different crankshaft position info.
Have you accessed the diagnostic screen to see if there are any codes?

Ray
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post #6 of 30 (permalink) Old 02-24-2020, 09:36 AM Thread Starter
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Originally Posted by RaYzerman View Post
The ignition pickup is behind the right side timing cover, the one with the large round access plug with the big screwdriver/coin slot in it. The wires travel up the forward side of it in a clip or two, then up under the throttle bodies to connect to the main harness. If there was a cut/chewed through/broken wire, the bike would not start. If pinched by removal/replacement of the timing cover, bike can run rather crappily since the ECU is not getting clean signals.
Other sensors... if coolant temp or cylinder identification sensor is unplugged/no circuit, bike will not start. ECU inteprets signals.... coolant temp will affect richness at cold, normal at hot. Intake air temp sensor (ambient air in airbox) will adjust mixture. Any corrosion/partly shorted wires/shorted can also affect what the ECU sees. MAP sensor detects vacuum and altitude, sends a voltage to the ECU.
I would unplug the ECU and replug just to refresh the connections since it's been sitting. Try manually moving the crankshaft (right timing cover, 14mm socket, rotate clockwise) say 90 degrees and see if the one injector still shows constant ground, i.e, ECU given different crankshaft position info.
Have you accessed the diagnostic screen to see if there are any codes?
Yes the self diagnostics are very helpful but no codes are being triggered. I replaced the entire harness including the plug that goes to the ECU. All wires are exact same color and location in the plug. The ignition sensor, must have 4 different points at which it fires. I’ll start with tracing those wires and pulling that cover. Thank you
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post #7 of 30 (permalink) Old 02-24-2020, 10:49 AM
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Pic of ignition pickup, I'm not sure you have to go in there, nothing much to go wrong. Trigger wheel is item 2, ignition pickup is the item below it, and to the right of the 1 as it exits the case...





Ray
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post #8 of 30 (permalink) Old 02-24-2020, 12:27 PM
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If the bike starts and runs it is not the pick up or other sensors. A noid light is used by plugging it into the harness connector for the injector. When the bike is cranking or running the noid will flash with the grounding pulses of the ECU. A test light is difficult to uses in this situation. If you have a individual injector lead grounded, free it from the harness and inspect carefully. You may need to cut it off and replace it with a tested good one from your old harness. If after you cut it off, if the bare end of the ground wire to the injector is still grounded, you most likely have a bad ECU
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post #9 of 30 (permalink) Old 02-24-2020, 03:26 PM
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With the age of the bike 2003 and knowing how the damp can get into the wiring harness connector blocks i would start by checking them first.

Under the tank under the T bar there is about 6 of them then there is one i think under the n/s fairing on a 03 bike.

That is as long as the injector is not gummed up?

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post #10 of 30 (permalink) Old 02-24-2020, 07:37 PM Thread Starter
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Originally Posted by mobilemike View Post
If the bike starts and runs it is not the pick up or other sensors. A noid light is used by plugging it into the harness connector for the injector. When the bike is cranking or running the noid will flash with the grounding pulses of the ECU. A test light is difficult to uses in this situation. If you have a individual injector lead grounded, free it from the harness and inspect carefully. You may need to cut it off and replace it with a tested good one from your old harness. If after you cut it off, if the bare end of the ground wire to the injector is still grounded, you most likely have a bad ECU
I have a Matco solid state diode test light that senses power and ground. It’s picking up all the other injectors pulses. The #1 injector is showing a strong ground with no pulse Upon performing the self diagnostic test that the bike has all injectors have a clicking sound of the injector opening and closing. The #1 injector does not click I thought it might have been clogged so I pulled the rail and cleaned the injectors with compressed air and injector cleaner they all had a nice pattern and they all turned on and off with the 9v power supply I rigged up. I have a suspicion it’s the ECU but was going to exhaust all other possible causes first
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