CDI Igniter Box testing

I thought I had hear that Yamaha dealers had a way to test the igniters. Anyone have any information on that? I would prefer not to try swapping in a known unit just in case something in the non-running bike does something to it (obviously slim but could a potential power surge fry it??) It is off a XJ550 Seca. Thanks in advance.

 

Yes, the way they "tested" a suspect TCI was to swap in a known good one and see if that solved the issue (that's actually the last flowchart action for testing the ignition system).

If I recall correctly, the 550 TCI case can be opened up (it just has screws that hold the cover one), so you can inspect half of the circuit board for burns, bad solder joints, etc.


TCI UNITS:

Yamaha (thankfully!) used a TCI (which stands for Transistor Controlled Ignition) system on all XJ-series bikes to control the coils, timing, spark advance, etc. A TCI unit is an "early" version of the now-common electronic control systems that are used on virtually all modern vehicles of almost every type, and even these early versions are completely maintenance-free and very rarely cause problems...........which is a good thing, because original TCI boxes are no longer available new.

When engine performance problems develops, many people immediately suspect that the cause may be within the "black box" workings of their TCI unit, which is unlikely. The factory service manual gives "instructions" for diagnosing TCI problems, and it basically says "test every other possible cause for your problem and if no other cause for the problem exists, only then should you "suspect" TCI failure, but before you buy a replacement, first try to find a known, working TCI unit from a similar bike and plug it in on the problem bike, and see if the problem goes away............"

Well!

There are three main problems that TCI units succumb to after years of reliable service:

1) bad solder joints on some of the internal components (known as "cold solder joints") result in the component pieces coming loose from the circuit board, and thus they can no longer perform their function reliably (or at all).

2) component failure......a blown-up transistor, a burned circuit trace, etc. This situation can develop if you have a short-circuit in your electrical system, or hook up your battery or jumper cables incorrectly, etc. TCI units do not like "big blue sparks" in the electrical system (except at the spark plugs, of course!).

3) another common failure of these units occurs if the TCI is continuously grounding the ignition coil (i.e. its output driver is shorted). You can verify this situation with an ohmmeter with the following tests:

- disconnect the 2-pin plug at the ignition coil and measure from the orange or grey wire to the chassis. You should see very high resistance. This should be pretty close on both the working and non-working channels.

- if you read a few ohms of resistance or less, then the TCI is bad. A shorted driver will also make the ignition coil run very hot and may ruin the coil.

4) dirty external terminal connections.


Bad solder joints can be repaired by someone who is skilled at that sort of diagnosis and repair, and even individual circuit components can be replaced, but it's tough to find someone in the modern world of "pitch-and-plug" skill-sets who actually has the skill and patience to do this type of work. Yamaha gave absolutely "zero" electrical specifications for checking the condition of the TCI units, besides the afore-mentioned "check everything else first" type of diagnosis.

But you can perform a simple set of tests to determine whether your TCI unit is good or not, without having a second, known good unit to install in place of the suspect unit. Although these instructions were written for XS owners, the exact same thoughts apply to the TCI units on the XJ-series of bikes:

http://www.xs11.com/forum/showthread.php?t=38224&highlight=tci+repair

The above is stolen, borrowed or even plagiarized from Randy Rado's site before it went away. It does require an analog meter as digital multi-meters do not show the swing of the needle that is required to test it.

"Using a voltmeter set on 12VDC, connect the positive meter lead to the Orange or Grey pick-up coil lead at the TCI. Connect the negative meter lead to the black (negative) lead at the TCI. Turn on the ignition. Voltage should come right up to about 10 - 11VDC. Crank the ignition and observe the meter. Look for a wide voltage swing during cranking. A strong swing indicates that the pickups and TCI are working OK and your trouble is between the TCI and the plugs. Possibly a bad ballast resistor, bad coil, bad plug cap or just corroded connections. Repeat this test for both Orange and Grey coil leads."

Remember that the Red wire with the white tracer stripe should always be hot with the key on. The TCI unit grounds the gray and orange wires from the ignition coils. The ignition coils fire when the TCI interrupts the ground.

The tricky part is the TCI un-grounds the gray and orange if there is no signal from the pick up coils for a few seconds. This is to protect the coils from overheating if the key is on and the engine isn't running. So unless you check the Red/white wire to gray (or orange) really quickly, you might get false readings or a mis-diagnosis of the true nature of the problem.


All of the XJ-series TCI units are of the "4RO" style as described in the above article.

Video here:

http://s307.beta.photobucket.com/us...4.html?&_suid=1354140627504033601775276167517


And if the above isn't enough, if you feel the need to get medieval with your TCI unit, well, then it doesn't get much better than this:

http://www.jetav8r.com/Vision/IgnitionFAQ.html

and this:

http://xjbikes.com/forums/threads/old-yamaha-diodes.32519


And for those who just can't resist a good Resistor (or transistor), here you go:

http://xjbikes.com/forums/index.php?threads/37190

and Holy Dark Mother of Fibre, don't try this at home kids!:

http://xjbikes.com/forums/index.php?threads/38234


One of the peculiarities of the TCI is the need to have at least one ground path for each secondary coil winding when checking for spark, or the TCI could (more like will) be damaged. For that reason you should never have more than one spark plug wire disconnected at any one time while cranking, and check for spark one plug at a time by grounding the plug to the head.

In a situation where you would want all plugs out…….for example, compression testing of the engine……then it is recommended that the TCI be unplugged from the main harness before testing is undertaken.


By the way, the TCI needs a minimum of about 10VDC to operate......and while the starter will spin the engine over like mad with low voltage, the TCI falls on its face at less than 10 volts.....which can lead to all sorts of confusion when a battery low-voltage condition occurs!