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.
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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
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.
There's a lot more in the Ignition Control Module than a darlington
pair. As I see it:
1: Tach output
2: Coil output
4: TDC pickup
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.
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
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.
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.
I have looked long and hard at the photos of the ignitor. The darlington
device is definitely from STM (http:/www.stm.com). The part number is
hard to decipher, but I am quite certain the first line of the part
number is BUxy41. I can't for the life of me see if "x" is actually a
character or just picture noise. The "y" looks like an "8" or a "9". The
second line of the part number almost certainly is "ZT". This is
consistent with "BU941ZT", which is an actual STM part number with a
package type like the one in the ignitor photo. The description is "HIGH
VOLTAGE IGNITION COIL DRIVER NPN POWER TRANSISTOR". See
http://www.st.com/stonline/books/ascii/docs/5288.htm for details. The
data sheet is at http://www.st.com/stonline/books/pdf/docs/5288.pdf . The
data 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.
The diode is INTERNAL to the transistor package.
Probably on the same substrate as the xstr.
I found ICs that were specifically designed for ignition control and
driving the Darlingtons,but none with the same pin count of the IC
pictured,nor any similarity to its part number.
I do not believe it's an optocoupler,but a full control IC.Probably with
circuitry to square up(shape) the drive pulse,and provide enough drive
current,and IIRC,the ICs monitored and regulated coil current.(that would
enable faster switching)
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