Ignition cut-out

Page 2 of 2  
wrote


I doubt a starter will crank the motor fast enough to make any significant reading on the tach. What's the smallest RPM indication on the tach,100 RPM? No starter turns the motor that fast.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jim Yanik wrote:

Well, FWIW on my wife's Integra I see the needle bump around zero when it starts. It would be interesting to see if it still does that with a bad ignitor..
Remco
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

Remember that the internal circuit of the "igniter" has an IC to measure coil current("dwell")and provide the proper drive to the Darlinton current switch. The tach drive could come from the IC. I haven't yet found the exact IC number to provide a datasheet to examine,to know for certain.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

coming from the

easily taken the

little) and

that can go wrong,

can use at as

noticed that while

cranks and the

is bad..? That

any significant

Doesn't this assume that it's mechanical motion of the crankshaft or camshaft that actuates the tachometer? If so, I'm not so sure I buy your reasoning.
I thought it was strictly a digital signal from the igniter (in particular, its computer chip) that actuated the tachometer. That is, the igniter computer chip certainly is not actually sensing degrees of crank- or camshaft rotation. Instead it receives signals from the ECU to excite the base of the igniter's transistor yada, in proportion to the rate at which the primary of the coil is supposed to be energized. This of course determines the plug firing rate, which will certainly determine, ordinarily, the engine RPM. The computer chip "measures" engine RPM through on/off switching of some kind (and so is digital and not analog in nature?). I would think that the momentary signals from the ECU at starting may very well cause something like noise in the tachometer signal, causing it to jump a bit.
Again, Tegger's site puts a lot of emphasis on watching the tach to diagnose a bad igniter.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elle wrote:

Makes sense to me. If the ignitor's drive comes from the ECM and clearly fires when the car is starting (one needs spark, after all), you should see it on the tach, albeit at a very low frequency.
I had not read tegger's page on the ignitor in quite a while until today. Seems like you can indeed tell by looking at the tach wheter the ignitor is bad. (That site is quite a great resource, isn't it? He's done a hell of a job on it - can't get over that every time I visit it..)
Remco
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tegger's site:

a hell of a

Today I was reading his fairly new "online OEM parts sources" site. Quite an interesting read. I hope to try the Colorado online parts store he lists sometime soon. Its shipping appears a little more straightforward and may be cheaper than Majestic's or SLHonda's. The parts prices themselves look about the same.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

But during CRANKING,the ECU reads the crankshaft (CK)sensor to determine firing pulses to FEED the igniter.So,tach pulses are still dependent on the ECU and engine RPM.

No,the crankshaft sensor is doing that. Spark plugs fire -at a certain position of the piston in each cylinder- ,determined by the ECU,thru the CK sensor.Not by RPM.

You have it backwards.On *starting*(cranking),the CK sensor reads engine crank position,and the ECU reads that and calculates the triggers for the igniter.The starter determines the cranking RPM,the ECU reads it thru the CKsensor (piston position)and triggers the igniter,where a supplementary signal is tapped to run the tach. BTW,the igniter fires the coil *4 times* for each revolution of the crank,so the tach circuit divides by 4 to get true RPM,or the igniter IC does that internally.Probably the latter.

The IC inside the igniter is to optimize coil current for hottest spark,and provide proper base drive for the Darlinton.The coil generates it's HV on the *shut-off* of the Darlington (that's the "flyback" pulse),not the turn- on,which is only to *charge* the coil's magnetic field.The IC is there to insure the coil gets a full charge no matter what RPM,that used to be called "dwell time",the time the points were closed and charging the coil,flyback and HV occuring when the points *opened* after charging the coil.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

input
it a

we
honda
ignitor
make
so,
(CK)sensor to determine

dependent on the

igniter
is
rotation.
each cylinder-

base
rate
rate,
RPM.
I just omitted the effect of the CK sensor. The main point--that the signal to the tach is digital and in response to the ECU signal, and may be sufficiently electronically yada noisy to yield some jiggling of the tach upon starting--stands.

triggers for the

reads it thru the

supplementary
Yeahbut while starting, well within one camshaft revolution the ECU is signalling the igniter, whose computer chip is still signalling the tach.
I'm just saying ISTM there's some kind of signal to the tach being generated, starting well within one camshaft revolution.

revolution of the

I believe you mean for each /two revolutions/ of the crank. It's a four-stroke engine; takes two revolutions for each piston to have gone through firing TDC (in a four-cylinder car) once; etc.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

FWIW, there's no real reason to "NOT" have it fire. There's just nothing there to burn half the time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

crank.
each
four-cylinder
Sure there is. For one thing, it would shorten the life of spark plugs, wires, and coil, potentially by quite a lot.
Weird comment...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote

Meaning there's ON and OFF and no inbetween.

The jitter would be due to normal timing variation of firing pulses from the ECU/CKsensor system,not from "noise" which would not affect a digital signal.(after all,it's a closed-LOOP system.) And the inertia of the digital to analog conversion to drive the tach needle smooths out jitter. The tach jitter is essentially meaningless,as the motor is not turning fast enough to give a true indication of RPM,RPMs being below the minimum calibrations of the tach dial. Note I previously said "significant reading".

Actually,I think the RPM calibration begins at a few hundred RPM,then linearly increases from there.

(well,the igniter chip is not a "computer" chip,it's analog;a current- sensing comparator to insure a full coil charge,that "dwell" stuff.)

Yes,the tach pulses get generated,but not enough pulses or fast enough to be significant.I haven't gotten a look at the specific circuitry of the igniter IC to be sure that tach pulses would not be generated even if the Darlington was blown and no current being switched thru the coil.The ECU could be triggering the IC and tach pulses passed on,but no Darlington drive or a dead Darlington.

You got me there.
--
Jim Yanik
jyanik
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

tach
firing pulses from

Sure. I was being loose with "noise" and probably crossed the line to inaccuracy.

AFAIC, noise can be a problem, regardless of whether the system is closed loop or open loop.
For example, the ignition system has a radio noise condenser in it (meaning, I hope as you know, this condenser reduces interference with the ECU, the car radio, and probably the igniter's transistors. Reports from two of our regulars here are that this condenser's removal or aging can definitely adversely affect ignition and so engine performance.

drive the tach

not turning fast

the minimum

Meaningless as far as indicating actual RPM. Meaningful as far as possibly using it to diagnose an igniter failure. Or so it seems to me for now.
I don't agree or disagree with the rest. My only interest was proposing that the Tach response could give an indication of igniter mis-operation. No disrespect intended; I prefer to get the bulk of my electronics lessons from other than Usenet. It's too hard to communicate important detail on internet boards.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
===========================================================TOPIC: Ignition cut-out http://groups.google.com/group/alt.autos.honda/browse_thread/thread/e8a5fd8cba927459 ===========================================================

snip
Most interesting.
.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.