Cylinders 2 and 3 won't fire. Coil is good

Hey guys, needing some help troubleshooting here; not really sure where to start. When I bought the bike it was running rough, but I thought I could fix it easy enough. Needless to say it's been a bit more involved than I thought it would be ... Finally got it put back together this morning (bent intake valve) bought a new battery yesterday and got it charged up, carbs are clean, new petcocks, new plugs, etc. etc. I even bough a new ignition coil, because I suspected it was a bad coil causing it to run rough. Cylinders 1 and 4 run, but 2 and 3 do not. Swapped coils so the known good one is on 2 and 3, and the new one I bought was on 1 and 4; same results ... something is wrong either with the ignition unit, or with the wiring that goes to 2 and 3.

To be honest I'm a bit overwhelmed at the moment, and frustrated with the amount of money I've spent on this thing (considering I've only been able to ride it once). Still have another $400 - $500 that I need to dump on it I'm betting, and now whatever this issue is on top of that. I'm going to walk away for a bit and drink a beer; hopefully one of you brilliant people will have a helpful suggestion by the time I get back.

Thank you in advance!

 

Finished my beer, and no replies .... guess I'll have another and read through this troubleshooting guide that I just found.

http://xjbikes.com/Forums/viewtopic/t=21932.html

 

Pull the plug wire for #1. Using a spare plug, or the plug for #1 if you have no spare, ground the body of the plug to the head and check for spark as you thumb the starter. The spark will look weak if you're used to checking CDI, or other, more-modern ignition systems.

 

Seems as though I've got a loose connector and/or shorted/open wire somewhere between TCI and coil; I'm getting roughly half the voltage at coil for cylinders 2/3 than I'm getting at the other. (measuring this with the key on, bike not running) .... any suggestions on where to start looking for this? Wind has picked up here in New mexico so I'll be putting it off until tomorrow after work.

 

I'm not sure how this would help me since cylinders 1 and 4 are the ones the bike is running on, and are therefore good....

I do have extra plugs, and can check this on cylinder 2 or 3, but based on what I was seeing with a voltmeter yesterday, I'm 99.9% sure I don't have spark on either of those cylinders.

 

The two coils get their power from a red/wht wire that feeds both coils. Clean the connecter that the two wires from the coils plug into. While the two red/wht wires from the coils are disconnected, measure the resistance between the r/w and the orange on one, and grey on the other coil. Between the r/w and org, you should read 2.5 ohms +/- 10%. Same with r/w and gry.
Remove the plug boots, and measure the resistance between the two plug wires. You should read 11K (11,000) ohms, +/- 20%.
The pick up coils have a test for them, 120 ohms between the B and Or, and B and Gy. They will be the small gauge wires in the 4 wire plug. (I think, my XJ is at another garage, and I can't remember the precise layout.)
A test for the TCI is to take a test light, poke it to a battery +, hook the clip to the grey wire at the disconnected coil, and crank the engine. The light should blink. Then try the orange wire at the disconnected coil. You want to hook the test light clamp to the orange and grey wires that go to the TCI. It breaks the path to ground when it gets a signal from the pickup coils. If either color doesn't blink, and the other does, the TCI is shot. Don't throw it away if it is, I am looking for one to do a post mortem on.
Let us know what you find. CZ

 

New brain fart here. Take you ohm meter, and pull the plugs on the TCI. Measure the resistance between the terminal that the orange wire from the coil connects to, and a good ground.
Then try the terminal that the grey wire from the coil connects to and a good ground. They should both read about the same.
There are two big transisters inside the TCI which act as switches, and normally they conduct to ground, until the TCI shuts them off, causing the coil to fire. If one of them went out, it might cause the indications you saw. Just a WAG, let me know , by PM if you want, what the outcome of the measurements is. CZ

 

You can't tell anything by checking the voltage at a coil with the key on and the system not 'in motion.' Each coil gets a voltage 'trigger' from it's respective pick-up via the TCI. Only diagnostic measure for coils is primary and secondary resistance as CaptonZap detailed. The TCI test is more complicated but you can easily check to see if it's getting the trigger voltage from your pick-ups.

Your TCI could be bad. But step-by-step is the only way to know for sure. Have you tried removing your caps, stripping new wire and reattaching the 2&3 caps to make sure they are making solid contact.

Electrical probs can be VERY frustrating, but don't over-think it. The only truly complex part is the TCI, eliminate the other possibilities first and if nothing else remains your in for TCI surgery or a 'new-to-you' TCI.

One last thing. Although your description and symptoms point towards electrical. It takes three to tango, compression, spark, and fuel/air mix. Have you checked compression, how are your carbs pilot circuits-you did those when the carbs were cleaned right?

 

I had this problem myself and it turned out to be the TCI. In my case, the transistors in the TCI were toast - one showing some heat damage and the other completely destroyed. A technical genius repaired/rebuilt it for me as a learning experience as my bike is a Maxim-X and TCI's are very few and far between.

 

Thanks CaptonZap, I'll go through this tonight and see what I can find. Haven't had a chance yet this week. As for your second post; I've been wondering myself it's something in the TCI that's fried. If so not sure what I'll do since those are made of unobtainium. Anybody know if the TCI from any other model would work? Even that would be hard to find, but maybe not quite so bad. Rare bikes sure do have some disadvantages.

Thanks MercuryMan, I didn't think about the system being "in motion", but it makes sense that I would see different voltages depending on where the pickups/engine were sitting when I tried it that way. I didn't try stripping or re-attaching the caps, but I swapped the coils, and the bike runs when using the coil for 2/3 on cylinders 1/4 ... I'm 99% sure that it's an electrical issue going to the coil; just not sure if it's TCI related, or something with the wiring between TCI and coil. If it ends up being the TCI I may try and rebuild it myself. I've not checked the compression, but the carbs are good to go I'd have liked to replace the pilot fuel jets because the heads were in less than stellar shape, but the jets themselves were clear and the correct size and since no one in town had them in stock, I just put them back for now.

That's what I'm afraid of .... the XJ1100 is also extremely rare (only sold one year in the US) and so parts will be high if it ends up being the TCI. Here's hoping that's not the case.

 

While a replacement TCI will be expensive, the parts that are in your TCI aren't. If you determine that your TCI is faulty take it to a TV or radio repair shop, unless you have done component level repair before. THe most common failure is the electrolytic capacitors. If you're lucky you can have your TCI fixed for under $40.

 

[quote="geissingerj I'm 99% sure that it's an electrical issue going to the coil; just not sure if it's TCI related, or something with the wiring between TCI and coil.
[/quote]

Here is how to check that. Unplug the 8 prong connecter at the TCI, and unplug the grey wire at the coil. Measure the continuity between the grey wire in the connecter, and the grey wire at the coil. If next to 0 ohms, thats good.
Unplug the four wire connecter, and measure the resistence between the grey and black wire in the connecter. That measures the continuity of the pick up coil. It should be 120 ohms +/- 20%
Check the voltage at the red/white wire at the coils with the ignition on. You should have 12+ volts with the engine not running.

CZ

 

If it is determined that the TCI is at fault and you elect to have a Pro from an Electronics Shop solder-in some new Caps or Transistors ... review the procedure for exposing the Board and component parts.

Getting down into the IC Board requires some finesse.

Print the Repair Instructions

TCI's ~ Transistors
CDI's ~ Capacitors

http://dave_jack.tripod.com/id41.htm

 

I would try to source a spare known good TCI, even if you get yours repaired. Them things are like gold....

 

His question about "just not sure if it's TCI related, or something with the wiring between TCI and coil" was what I was giving him a way to resolve.
The TCI gets power when the key is turned on, and after a few swconds, if it doesn't sense reluctor revolutions, it cuts down the power to the coils, so as not to over heat them. So if you set your meter up, and turn on the key, do not hit the starter, you will see a rise in voltage, and then a drop. This indicates that the wiring to the TCI is getting power to it, it is sending power to the coils, and the coils are dissipating the power. You've checked three things at once. If the power doesn't get to the coil, you go back the the TCI and check the power coming out at the grey and orange wires in the 8 prong plug. If it comes out there, you know that there is a wiring problem between the TCI and the coils. If you don't have power there, you can assume that there is an internal problem with the TCI.
Clear as mud? :? CZ