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Discussion Starter #1
Where to start? four days ago I went out and about a minute from home the bike started to sputter, miss and backfire. Within 30 seconds the front cylinder had gone dark and I had to limp her back home on the rear only. The rear was as strong as the front one was dark. Getting her back I started checking the usual suspects, battery connections, spark plugs etc. to no avail. The next day I swapped the front plugs to the rear and tried to start her. At first it was only the rear cylinder again, then a few seconds later the front began sputtering back from the grave and within 30 seconds, she was running as clean and regular as ever she had. Shut her down and started her again.... several times. Every time she fired right up and sounded great. (Yes, an intermittent failure, just great.) Shut her off again and got my wallet to go get some gas and when I fired her up again, she was once again only liking the rear cylinder and the front was dark once again. However, this time it compounded. within a minute the rear cylinder began to miss and backfire and in short order, it to went dark. Any attempt to start her after that has failed miserably.



She has such a weak spark and 90% of the time I can't even see any spark.
Now absolutely everything else works fine.

As of this moment I have performed the following checks and procedures in search of the culprit.


-Checked fuses, including the two 30amp mains on the left side to the rear of the starter solenoid

-Checked gas and swapped it out
-changed plugs
-checked the grounds, (did the full ground fix 7 months ago)
-Disconnected my PCIII and checked the TPS wire for any damage where the PCIII is piggybacking the wire. (Soldered and sealed with no issues)

-starting in the headlight bucket and working my way back, pulled, checked and reconnected with di-electric grease, every connector I could find.
-Traced and tested continuity in wires from and to the ECM for the Camshaft position sensor, Crankshaft position sensor (Ignition Pulse Generator), Coils, Injectors.
-Tested fuel pump pressure
-checked for fault in fuel pressure regulator
-checked resistance of Primary coil windings, both within the 3-4 ohm range.
-Checked resistance and possibility of short in the secondary coil windings
-Swapped the ECM with a friend
disconnected and checked resistance/continuity of Crankshaft position sensor
-Checked for same resistance reading at the ECM connector


All to no avail. Nothing found to be amiss anywhere yet. Still, no spark.


Am building a Peak Voltage Adapter for my multi-meter tomorrow and then test the output of the Crankshaft Position Sensor and coils.


Any and all help with this would be greatly appreciated.
 

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Still using the cam position sensor for a tach feed??? If yes - Take it off.

What is the secondary coil resistance measurement?? 32k -36k ohms???

The Secondary Ground wire at the PCV aka brake proportioning valve.
Check at battery and at frame connection.

The most likely:::
>>The 2pin connector near the Starter Relay with Red, Red/White wires has burned open a few times.
>>Those wires go from 30 amp fuses to the harness.
Red/White wire is the battery feed to the FI system.
https://tech.bareasschoppers.com/tech/melted-main-wiring/

Trouble shooting - look for voltage loss.
High impedance meters will read voltage that would be open if it had a load attached.
 

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Discussion Starter #3
The tach wire that was attached to the cam position sensor was one of the first to be disconnected.

Checked the main power connector by the starter relay yesterday and it was nice and clean, without any indication of overheating.

Secondary coil resistance rings through at 32.4k rear and 32.6k front.

The two connections for secondary grounds including the one by the proportioning valve and one at front coil were removed and checked. (Still clean and greased from last seasons ground fix)

Threw together my Peak Voltage adapted today and tested at the ECM connector, the crankshaft position sensor(ignition pulse generator) peak voltage. It was outputting 6v which is well above the minimum 0.7v.


Initial static voltage from Bu/Y to ground, Y/Bu to ground and both B/W to ground showed battery voltage (12v).

Primary coil peak voltage from Bu/Y to ground and Y/Bu to ground measured 160+ volts for both front and rear coils.

Peak coil voltage from B/W to ground produced a voltage of 11v

What I didn't find though was an initial battery voltage across Bu/Y and B/W or across Y/Bu and B/W.

Still no discernible spark is found.

Thanks again for your suggestions and input.
 

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Quoted>> Initial static voltage from Bu/Y to ground, Y/Bu to ground and both B/W to ground showed battery voltage (12v).
Quoted> What I didn't find though was an initial battery voltage across Bu/Y and B/W or across Y/Bu and B/W.

The IGN coil driver is OPEN, therefore the voltage is the same as the Initial static test.
Only during cranking or running when the Bu/Y and Y/Bu is pulled to Ground is current flowing in the coil.
Primary peak voltage 160 volts proved the coil was energized and had a high voltage produced by the collapsing magnetic field.

No spark but you have continuity.
This no spark is using the existing spark plugs with sparkplug shells grounded????

Bad spark plugs or spark being shunted to ground or internal arcing.
The IGN coil test in the SM shows about the same .

One secondary coil - the sparkplugs are in series. Like two lamps in series, one burns out the other one will not light up.
 

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Discussion Starter #5
Hans&Feet You are the man. I am usually pretty good at this sort of thing and not a slouch with mechanical or electrical issues, but this one had me stumped. All my previous experience was with non computerized bikes and single coil per plug bikes that had the secondary coil complete the circuit via one leg being grounded. This system of grounding through the opposing plug. Even a center tap of the secondary to ground would alleviate this issue of one bad plug/boot/wire knocking out the whole cylinder. Then they would both fire as they should, but they would also act as redundant circuits against the failure of one. Anyway, I had swapped the plugs with an old set that I replaced while they were still good. Low and behold, she fired up and screamed to be taken for a ride. For this, I thank you very much. It was your explanation of the secondary circuit specs. I still did not think that both the front and rear cylinder would have a bad plug each, but it seems it was exactly the case.



Kudos and thanks to you. Cheers.
 

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Wayne, I was impressed by your testing abilities!
Building a peak voltage adapter also.
I made one a few years ago. I measured peak voltage while running, 174 DC volts at idle, 276 DC volts at a few thousand RPMs.

2002 had cold spark plugs that fouled out. 2003 and later used a spark plug one range hotter.

Oscilloscope on bench with Accel coil with exact same purpose as a VTX Ign coil but this was for an S10 firing different cylinders.
 

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