Ignition updates to the Unofficial FAQ

Good job, John. Thanks!

"Remco" wrote in news: snipped-for-privacy@g44g2000cwa.googlegroups.com:

Thanks.

Thanks are also owed to all those (including you) who helped by supplying much valuable information.

Tegger, Thanks again for your help. I just wanted to let you know that I received a letter from Honda and the title of the recall notice was: Ignition key is removable with the shift lever out of Park

I took my Honda to the local Honda dealership and they installed the following as per the service report:

1 06351-S84-000 KIT, LEVER (A)

I don't know whether the first number 1 is part of the part number or means that only one kit was installed. I hope this helps. I have not yet had a chance to revisit your web site.

A little adjustment to the graphics:

The darlington pair is the switch. Pin 3 would be the pulses from the ECU or magnetic pickup. The tach connects either to the primary winding (which makes radio interference) or to whatever drives the transistors.

And yes, the ignitor gets flyback voltage too. Some electronic ignition systems still need the condenser because the flyback voltage on the primary side otherwise rises extremely rapidly. It can rise faster than some high voltage transistors can turn off and it can even rise before the spark plug discharges the energy.

interesting. i had 2 igniters fail inside a year on my 89 civic & subsequently discovered that the condenser had failed. presumably, excess flyback was responsible. but, my 91 crx has no condenser at all, from factory. what's up with that? works fine, no r.f problems. both have the same igniter. any thoughts?

The coil might have an internal condenser or a small shorted winding. An oscilloscope on the primary coil would show you what's going on.

I'm doing this from memory so the shape might be a little off:

v- Spark plug discharge

| | |# |## | | | | | |

--- | -------------------------- -----------

^ ^ ^ flyback | charge open circuit

Without a condenser, the initial spike is much higher and it rises so steeply that it might not produce a visible trace on the oscilloscope.

|

.

.# ## | | |

--- -------------------------- -----------

makes sense. i have an old scope so i can check between the two. thanks!

Kevin McMurtrie wrote in news: snipped-for-privacy@corp-radius.supernews.com:

Take a look at this, from Graham W.

So how would I show that in the graphic? If there's a cap somewhere to blunt the flyback, I'd like to have that shown.

There's a lot more in the Ignition Control Module than a darlington pair. As I see it:

1: Tach output 2: Coil output 3: +12V 4: TDC pickup Case: GND

The TDC sensor produces a curved waveform. Integrating the form (high-pass) can produce the advanced timing needed for dwell.

Maybe Jim Beam can take a photo of his o-scope. My new Honda has a coil on top of each spark plug so I'm not sure I can tap into the primary coil. I have a circuit that drives coils but it's not quite the same as a car ignition. Want a picture of that trace?

i too was under the impression that the igniter handled dwell because i know that happens with some other ignitions, but it seems that with the honda, all that's taken care of by the ecu. #4 is the for the ecu's output signal. the igniter just switches as soon as it gets signal.

but that said, i do have the gear to test that properly this time... i have a spare working igniter - i'll do some more homework.

Kevin McMurtrie wrote in news:mcmurtri- snipped-for-privacy@corp-radius.supernews.com:

True. And I see that in these photos.

Here's another page to critique:

It's there.

It's there

It's there

According to the diagrams I'm seeing, such as

goes directly to the ECU. I think the TDC pickup goes directly to the ECU as well.

Yes, but not really nesessary to show in this context.

Sure! Thanks.

jim beam wrote in news: snipped-for-privacy@speakeasy.net:

That would really be appreciated, thanks.

looks like a good summary. obviously, as graham's pics show, there's more to the igiter than the darlington, but what you show is a good interpretation of the result. it's also worth mentioning that in both my igniter failures, there's been no code. terminal 4 is behaving as per normal, [hence no ecu] but the igniter output is failed hard "on" and switching the input makes no difference to output.

i think it's also worth showing the condenser & mentioning its role too. it's a $25 part & a pita to replace, but mine failed with a near dead short so even before the igniter failed, my car had been chronically weak & the exhaust way sooty because there was no strenght to the spark.

Kevin McMurtrie wrote in news: snipped-for-privacy@corp-radius.supernews.com:

I looked up the Darlington transistor that is depicted on the Honda igniter,and it has an internal diode to shunt the flyback voltage around it,to protect the Darlington.

Jim Yanik wrote in news:Xns96677D9AC821Bjyanikkuanet@129.250.170.84:

Got a URL or a pic? I'd like to add that diode.

The pics I found showed resistors, but no diodes.

probably not for a couple of weekends.

as a footnote to the condenser replacement, as i said before, both the failed condenser & the condenserless crx distributors produced no r.f. interference on the car stereo. but, if i was on the [hands free] cell in the car, people always used to complain about static, even though i couldn't hear any myself. tonight, [shows how bad it used to be that i'd not bothered with the cell in the car for this long] i had to make a call & i'm told it was completely clear! so the condenser /does/ make a difference, even if the car stereo itself is sufficiently well filtered to not be susceptible. this totally confirms kevin's rise rate explanation.

Cellphones operate at frequencies hundreds of times higher than the rise rate of the primary coil. What probably happened is that the rise rate was faster than the transistor could turn off. In some cases you can induce crazy RF oscillations if a digital circuit is forced into an analog mode. That kind of oscillation roasts a transistor in a hurry too.

The radio noise I mentioned is in cars like the older Toyotas where there was a long meandering wire between the primary coil and the ECU and tach. The 350V ignition pulses bled into everything. Aftermarket component stereo equipment needed braided shields over the interconnects.

I have looked long and hard at the photos of the ignitor. The darlington device is definitely from STM (http:/

The part number ishard to decipher, but I am quite certain the first line of the partnumber is BUxy41. I can't for the life of me see if "x" is actually acharacter or just picture noise. The "y" looks like an "8" or a "9". Thesecond line of the part number almost certainly is "ZT". This isconsistent with "BU941ZT", which is an actual STM part number with apackage type like the one in the ignitor photo. The description is "HIGHVOLTAGE IGNITION COIL DRIVER NPN POWER TRANSISTOR". See for details. Thedata sheet is at Thedata sheet shows the diode between emitter and collector. The IC in the photo looks like it has part number U2226B, and a good guess is that the TFK in the first line stand for Telefunken, a German semiconductor manufacturer later renamed TEMIC and eventually bought by Vishay. I have not found any data sheet for the U2226B, but I believe it is an opto-coupler.

Here are oscilloscope traces of an ignition coil with and without a capacitor: