Trying to test TCI ignition unit

[Brett]

Ok. I've spent a few more hours trying to understand what the problem is. I've checked everything I can think of. I've checked the old loom and all the common connections/colours are the same. I keep going through it, expecting to find some stupid mistake, but can't find anything.

I had made a mistake in my explantion above (which I've corrected - it was late and I was getting more and more confused!). With either of the wires (red or orange) to the coil unclipped, I get at least 12volts at the red wire to the coil (good - almost the same as the battery), but if both wires are attached to the coil, I get a one volt drop at the coil between the red and ground. Should that be happening??

Because of the readings I was getting from the transistor in the TCI box, I removed it to test it off the pcb. I got the same results with it off the pcb, with current flowing from E to C and B (supposedly meaning it was broken according to the transistor test on xs650rider). So I bought some new transistors (a couple of MJE5742 just to make sure). Even the new ones conduct both ways between B and E, so I don't think it's possible to rely on that test. (I did all this with a friend who is an electronics engineer.) Anyway, we fitted the new MJE5742 transistor and it makes no difference. So unless something else is wrong with the Ignitor, I admit that's probably ok.

There is still no spark when I kick it over, and as I said above, when I switch it off at the key or kill switch there is a single spark at both plugs. The standard tests (checking the resistance at each end) seem to show the coil is ok.

I'm now totally lost and have no idea what's wrong. Any more ideas?

 

[xjwmx]

and as I said above, when I switch it off at the key or kill switch there is a single spark at both plugs.

That would have told you that the transistor you've been suspecting was in fact good. If it was bad there would be no spark ever.

You say the coil measures good, but I've had two that measured good that would produce only a weak spark or no spark. I suppose because of a high voltage only path. You can have a path that conducts hv only.

If you're absolutely sure the wiring is right, then test the coil and tci by substitution. It's the only way unless they look blown up!

Check the pickup for the readings you can find on this board. It is sounding more like the pickup to me. Because you get a good spark but not in response to the trigger. I've had one go bad.

 

[Brett]

Thanks xjwmx. I'll check the pickup in more detail first then. I got about 730 between the black and the others. I'll check between the grey and orange and do the magnet swipe test.

The rotor tested bad after I rebuilt the engine so I had the rotor and stator re-wound after it was confirmed that they were both in poor shape. Not sure what the shop did with the pickup when they refurbished the rotor and stator - maybe it's a magnet issue.

 

[xjwmx]

I had the rotor and stator re-wound after it was confirmed that they were both in poor shape. Not sure what the shop did with the pickup when they refurbished the rotor and stator - maybe it's a magnet issue.

Could be, especially if it hasn't run since you got it back. Sometimes they swap the core and you get another one back. There are rotors with weak magnets or magnets that are farther away from the pickup than they're supposed to be. There's the radio shack magnet trick you could use to test for that. After you test the pickup.

 

[Brett]

Thanks xjwmx, but still found nothing. I tested the pickup and both coils seem ok. Over 700 between black and either of the other two, over 1400 between orange and black. I tried a magnet over each of the pickup coils and got a fluctuating reading for Ohms and voltage. With the ignition off, and the stator attached, I kicked it over with the plugs out and tested across the pickup wires as close as possible to the pickup and got the same fluctuations in resistance and voltage. So the pickup is ok. (At least I'm learning a lot as I do this!)

I've bypassed my kill switch and tested everything I possibly can think of - it's going to be an interesting one when I do find the problem!

I looked at the TCI pcb again (pic on first page) and there was a lot of glue over the black capacitor nearest the red 12volt wire. So I carefully picked it off and found a lot of corrosion/oxidation on the end of the capacitor, and the black plastic sheath around it has some lumpy corrosion under it - would this cause a problem?

xjwmx; you say "you get a good spark but not in response to the trigger", but that is only when I switch off the ignition - that's the weird thing and I'm sure a clue to the problem.

Has ANYONE got a spare TCI they could test for me? If I knew it was normal to get about 70 Ohms resistance between the ground and red 12 volt wire - OR the same resistance between the positive terminal at the coil and ground on a complete, working bike, it would really put my mind at rest.!

If I can get my hands on a spare TCI I could test it by substitution - I think that's my next step.

 

[Brett]

I bought and fitted another TCI ignitor and it started second kick! So it was the ignitor all along. (Even used, ignitors are not cheap so I'm glad it worked).

Out of interest, I tested the new ignitor for continuity between the ground and red wires and there was none, so this confirms that the reading of about 70 Ohms I was getting on the old ignitor shows it was bad.

Anyway it runs well. It should be painted, completed and on the road in a couple of months.

 

[xjwmx]

Congratulations! I wish I had time to ponder this and maybe figure out what was wrong. The 70 ohms thing, it might mean something or it might be within normal expectations. At any rate, don't throw the bad one out since it's probably fixable. At some point by somebody.

 

[njrmahoney]

I have read your posts about weak no spark with great interest, my 83 xs650 is having the exact same problem. Including the 1volt drop from ground to red/white wire on the coil. You say you bought a new iTCI ignitor and that solved the problem. By TCI ignitor do you mean Coil? you bought a new coil?

 

[nj1639]

I believe the igniter is the black box. Should be attached to the bottom of the battery box. I believe xj has a thread about making repairs and replacing components.