Hi,
I have a strange problem. My bike died 5h ago after 1h drive just when I was parking on the beach. It run ed great for 100km and died. I found out that there is a fuel flow to carbs.
Here is a strange part. When I disconect any s0arkplug cap from sparkplug it imidierly starts and iddle fine-rough but it idles. When I connect it back revs goes up a bit but it does not idle, dies ant won't start until I disconect a spark plug cap.
Sorry for all mistakes. When I was writing original post I was standing in the middle of nowhere trying to fix my bike in full sun for past 3h.
It appears that there is no spark when all sparkplug caps are connected to all sparkplugs. When I disconect one (doesn't matter which one tried from 1 to 4 bike starts immediately. I think it may be bad coils that heated too much from riding and failed. Am I right? How to test them - my bike is fj1200 1989 3cv.
That is a strange problem for me, maybe others will have better input.
Bike and coils cooled overnight and now it started/there is a spark with all sparkplugs connected. So it is related to heat I guess but what :)?
I can bee coils .they can stop working when hot .Check if there is any cracks on the underside of the coils
if it is throw it in the bin. I checked the coils on my kawa some days ago and took some picks .You can test the coils
on the fj the same way.Dont look at the readings i got on the picks.I posted the specs for the FJ coils from yamaha
manual in pic 4. If testing the ht wires with the sparkplugcaps on you sholuld retrackt 20 ohm on the reading because of the sparkplugcaps.I think the fj has 10 ohm resistance caps
On warm engine primary was 4.1 and 4.0 ohms, and now when it cooled its 2.4 and 2.2 ohm. Secondary is 13.5k on both, caps reads 10k
Quote from: gpspl on August 16, 2023, 06:11:38 AM
On warm engine primary was 4.1 and 4.0 ohms, and now when it cooled its 2.4 and 2.2 ohm. Secondary is 13.5k on both, caps reads 10k
Ok the manual says to mesure them when 20 degree celcius . On the secondary it shuld be about 32K ohm when measuring with the 10k plugcaps fitted onto the HT wires. Check how much voltage reaching up to the coils .I have posted a pick how to measure .in the pick i did it wrong i found that out later. Have not tested the coils the right way later because the bike runs well.
but i have tried to explain the right way to measure in the textbox on the picture. And try also to check underside of the coils for cracks if cracked they are toast.
Battery is 12.44v, coils gets 11.78v
Still looking for cause of no spark. Any idea what else I can test? Is there a test for ignition module?
You can test the pickupcoils like described in the picture from manual above. If i remember right you will not get spark if the sidestand switch
not working, same with the clutch switch and also maybe the neutralswitch. Check the 15A fuse to.You can check the killswitch to.I dont have more picks from the manual now. The clutch switch you can test by making a little jumpwire and take off the connectors at the handlebar
under the clutchreservoir and jump them .you can test that too on the sidestand switch connector it is placed under left sidecover and i think it is the green connector .It is not the red connector that is for alternator and usalli it melts .You can check if it is melted.I think that the voltage to your coils is to low but not sure i cant check that now because i dont have the manual here. You can check the sparkplug gap it should me 08-09mm .Check that plugs are clean and how does the spark look if it is yellow it is weak an may not fire the gas if it is strong and blue it is good. If you have checked all this and still dont get spark i have to throw in the towel (popcorn)
Checked and pickup is in spec. I just don't understand why it has no spark with all sparkplugs connected and the moment I unplug one it starts first crank, then when I connect sparkplug cap back it runs on all 4 but dies when rpm goes below 4k. Battery is new but just to be sure I connected battery from my other bike and still same. And why it happened suddenly like I rode for the past 5 days average 55 miles a day and died when parking :)
See if you can isolate the problem to just one coil. (The chances of both coils going bad at the same time are nil.)
Left coil powers cylinders 1 and 4
Right coil powers 2 and 3
Take off the plug cap on either cylinder 1 or 2 see if the same thing happens.
I did that, I'm fact that's how I returned home yesterday by unplugging 1 to 4 sparkplug every 25km.
It doesn't matter which sparkplug I disconect 1 to 4 it just starts. I also unscrewed cylinder 1 sparkplug and grounded it with wire there was no spark but the moment I unplug cylinder 3 sparkplug spark appeared on that first plug.
It's so unrealistic that I'm thinking this bike is cursed :)
So, removing either #1 or #4 causes the same thing to happen.
This does not happen with either #2 or #3, correct?
He stated unplugging any of the four leads would allow it to spark again. Very strange for sure.
I don't know why unplugging one would restore the spark. You might check that your ground connections are good. That connection would be common to both coils.
There is a test for the ignitor box in the electrical files section https://fjowners.com/index.php?topic=19679.0
It describes how to trigger the box to cause each individual coil to fire. I've used the method on my fj 1100's. I think it might work on later model ignitor boxes but I haven't had an opportunity to try it. The wires and colors are different on later models but the two wire connector that goes to the trigger coils is easy to identify.
Aaah, ok got it, thanks Travis....very strange indeed....only common thread between the 2 coils is the ground.
Just installed set of different coils and still the same. How to test ground?
Quote from: gpspl on August 17, 2023, 03:32:35 AM
Just installed set of different coils and still the same. How to test ground?
Was there an earthing cable under one of your coils fixing bolt?
Yes, there is eyelet connector ground wire bolted to coils
If there is no spark when all sparkplugs are conected what does it mean? Load is bigger or smaller?
Why when i start engine on 3 cylinders, rev it above 2.5k and connect missing sparkplug it runs and revs to limit but dies when below 2.5k?
When i keep it below 2.5k with 3 cylinders running and just "touch" unconnected sparkplug with cap it dies imidietly like there is a short or not enough power.
What connects all those things?
Maybe to try running a negative wire from battery directly to coils to check if it still happens? I don't know if that is a good idea, but that should tell you the ground quality. I don't know, might be corroded on the back of the engine where it is connected and not letting through enough current for all 4 spark plugs? Does it make any sense?
Did you check how much it charges?
I have a feeling that the DCI switches the earth to coils, so it could be in the black box as you've swapped coils.
You have checked/redid earthing to rear of motor?
Everything else electrically works so earthing shouldn't be a problem.
Have you tried another battery?
I tried another battery and still same.
But i have a finding, should orange and grey wires that goes to coils have continuity, even when DCI is unplugged?
Looking at wiring diagram i think it shouldn't :>, right?
Quote from: gpspl on August 17, 2023, 07:28:24 AM
I tried another battery and still same.
But i have a finding, should orange and grey wires that goes to coils have continuity, even when DCI is unplugged?
Looking at wiring diagram i think it shouldn't :>, right?
I mean there is a short between orange na gray coil signal wire. I unplugged coils and DCI and it's still there. Those wires should not be shorted right?
The gray wire coming off the coil is also the signal wire to your tachometer.
ok guys I fixed it.
It was a short between orange and grey coil wires where shorted. He'd to unwrap loom to find it but it's fixed. Thank you guys for all posts and help
Glad you found it...what was the cause of the wires shorting? Abrasion? Cracked insulation from heat?
To have a short buried a wiring loom bundle has to be the most difficult to pin point.
A common short in our FJ's is the power lead going down to the horn. The wire is hot (key on) as the horn switch simply grounds the circuit. The wire scuffs against steering neck on the frame.
Cheers
It was my poor wiring job. I relocated DCI and safty relay to the rear of a bike. I haven't stacked wires when splicing and shrink tube got pinched or something and shorted both wires - i redone my wiring remembering to stack wires and just to prevent this issue again used thicker shrink tubes and "cloth" type tape just to be sure. ( I made my fj1200 a naked/streetfighter, but don't worry no working or good looking fj was harmed in the process. It was wrecked. It's a theme with all my 6 bikes as I buy wrecked unwanted bikes and fix them and customize them for my liking. It was a last bike to make now time to move to fixing cars let's say datsun 280z :) )
I'm planing on Makin a writeup about whole process but now I want to enjoy my bike a bit:)