ECU Check on 2000 Faired

[Tris]

I think the ECU might be fried on mine

Can I check it in anyway or is just "test with a known good one" as it says in Haynes?

Cheers

Tris

[TSM]

When turning over then engine, does it backfire or just do nothing while turning?

Explain more what you problem is. It may be somthing else.

There is a CDI unit on the 2000 not a ECU, unfortunatly unlike on the later bikes K3+ it does not give diagnostic codes on the clocks.

[Tris]

Sorry I should have been clearer.

This was the start of it all http://forums.sv650.org/viewtopic.php?t=35405&highlight=

But when I turn the engine over there's no pops, no bangs ----- no nothing!

Thinking about it on the way in this morning I don't rember checking for a spark, so that's tonights job

Any other ideas though would be greatfully received though :shock:



Tris

[Carsick]

Being CDI they're an absolute ******* to test without specialised equipment.
Swapping it with a known good one really is the easiest way.

[TSM]

If it does not fire a spark & you have checked all the coil connections then its a good indicator that the CDI is up the duff.

Oh have you got an alarm fitted?

[Tris]

Checked for sparks - nothing :(

No I haven't got an alarm & battery is charged.

I know I've got continuity back to the CDI from both coils so I guess everything points at a dead CDI

Guess what the next couple of days job is!!!

[Sid Squid]

The SV ignition system isn't CDI, it's a conventional earth switched transistorised system - you can always tell as with a CDI the coil + aren't at battery voltage, in a CDI system the coil + is connected only to the ignition unit and not to the 12V supply.

Anyhoo Suzuki don't supply any test data for the ignition unit, so realistically the best way to check is swopping for a known good unit.

They are pretty reliable though, so it's worth making sure that all the wiring and the other ignition bits - pick up/throttle position sensor - are working properly, TPS shouldn't stop it running, but it's worth checking anyway. And at cranking speed there should be more than 3V from the pick up, but that's hard to check without a clever bit of 'leccy kit, so again, should you suspect it, substitution is the easiest way to find out.

[TSM]

Why do they call it a CDI unit if its not one?

[rictus01]

The SV ignition system isn't CDI, it's a conventional earth switched transistorised system - you can always tell as with a CDI the coil + aren't at battery voltage, in a CDI system the coil + is connected only to the ignition unit and not to the 12V supply.


OK, whos got the Boyer electronic ignition kit then :wink:

You're just confusing them now Ian, :idea: "box of Electrics" under seat is enough.

Cheers Mark.

[Carsick]

Why do they call it a CDI unit if its not one?
The same reason some call it an ECU.

I was genuinely under the impression it was a CDI (Capacitor Discharge Ignition)
Luckily, my basic advice of replace it has been agreed with, so I don't look quite so stupid.

[Sid Squid]

I think CDI is an almost generic term for electronic ignition now, although true CDI systems are rarer now than in the 80s and 90s.

Anyhoo:

CDI = Capacitor Discharge Ignition.

OK Listen up, some basics, said simple:

Electricity: Materials called conductors have lots of subatomic particles called free electrons, a current is when these are moved around a circuit and, for example, you can do this by arranging a magnet to drag them along a wire, a generator is a magnet spun around on a shaft with a coil of wire closely around it, spinning the magnet will make the electrons move along the conductors.

Ignition Coil: An inductor. A highly specialised example of a transformer. Two electrically isolated coils of wire on a common core, that is, one wrapped around the other, one called the low tension (LT) coil which typically has a few hundred turns of heavy wire, and one called the high tension (HT) coil which has thousands of turns of thinner wire. If you pass a current through one coil the resultant magnetic field also envelopes the other coil. Switching the current on and off - thus making the magnetic field build up and collapse - that is; move, induces (it's an inductor see?) a current in the other coil. For a points system the coil typically has a ratio of about 200:1, that is; the HT has about 200 times as many turns of wire as the LT, for an electronic system the ratio is typically 400:1.

Capacitor: A device that stores electrical charge, previously known as a condensor.


In what might be considered a conventional ignition, the LT coil is permanently live (~12V) and the earth, (neutral), connection is switched on and off* at appropriate times to produce sparks when needed, nowadays the switching is usually achieved electronically, in times past, (and still in my VW van), the switching is mechanical, the switch is known as the 'points', which are opened and closed by a cam turned by the engine. As above applying current to the the LT coil builds a magnetic field, but in electrical terms this happens quite slowly, however, when you switch off the current the field collapses rather quickly, in doing so the magnetic force moves across the HT coil too, dragging free electrons with it; it induces a current in the other coil. As the HT coil has many more turns of wire lots more electricity is induced in it, and the induced voltage is much higher - you don't get owt for nowt though, the induced current is much lower - this is OK though, we wants volts, lots of them** - this current passes along the HT leads to the spark-plug***. Now, that's bit that many people have found confusing: the spark happens when the switch is turned off, not on, this is because the field collapses much faster than it builds, the limitation is coil voltage, which in automotive systems is most commonly nominally 12V.

This was fine and dandy in points systems for many a year but as engine speeds got higher, and thus the amount of time between sparks fell, the time that the points would be closed became briefer and briefer (this is called the 'dwell' and is described as a percentage or given in degrees of ignition cam rotation), thus the time available to charge the coil also dropped causing ignition to suffer, the move to electronic systems improved things somewhat as the LT could be switched back on much more quickly after the spark which improved coil charging.

CDI still uses a coil but it works rather differently, it takes the 12V from the battery and, using a clever bit of electronic trickery called an inverter, raises the voltage, typically to about 300-400V, and uses that to charge a capacitor, when a spark is required the capacitor is caused to discharge through the LT coil, because of the high voltage the magnetic field builds super fast, inducing a chunky voltage in the HT coil and causing a spark, albeit one of relatively short duration, which is a limitation of CDI systems.

We generally don't use CDI systems now because 'conventional' systems design has been improved, coils are better, electronics are improved, and also CDI is a bit dearer. Until recently it was usual in a 4 cylinder engine to have only two coils, (each end of the HT coil of which is connected to a spark plug), each would provide sparks to two cylinders, one would be timed to cause ignition, and the other would occur on the exhaust stroke, the reason for this is simplification, there's only two timings needed for four cylinders, however engine speeds have risen again and more modern 4 cylinder engines have four coils, commonly incorporated into the plug caps, these only have to be fired half as often - plenty more time for coil charging and better quality sparkles.

Got it? Excellent!


* There's a good reason for switching the earth, (neutral), but don't worry about it now.
** Depends on the system, but 20,000 - 30,000V is fairly typical.
***Which is a whole 'nother story.

[rictus01]

Ian, you have way to much time on your hands :wink: