I have everything working EXCEPT i cant get the ecu to give the MSD its rpm input signal (adding a ground)

when i ground the white wire to the msd (simulating RPM) i get a tach signal, but the ECU will simply not trigger on its own.


posts like this one are just beyond my imagination, how the hell people are getting these setups to work. Im beginning to think it may have something to do with the AEM EMS?

https://honda-tech.com/zerothread?id=454245

so here the image for everyone who is curious.



so last but not least, does wiring the tach output to the alternator make any difference, as opposed to the wiring harness at the distrib point? OBD1 fwiw. Im stumped on this one...

EDIT: Ok just to clarify, the post is a bit vague

Blue wire on the harness (which formerly attached to the ignitor) now goes from the back of the MSD box to the wiring harness.

orange goes to coil
black goes to coil
red goes to battery
black goes to ground
little red goes to switched +12v

The problem exists here:

White wire on the MSD box (which is what the ignitor gives the MSD the signal to "spark") goes to the yellow/green wire on the harness. It goes from the harness to the ECU, it does not enter the distributor. The ecu triggers the ignitor by adding a momentary ground (i believe). Now, when i physically ground the wire for a quick second (to make the MSD think it is getting an RPM signal) the tach jumps around and thinks the car is running.

When turning the car over, there is no signal. The ecu will not output an rpm signal to the msd, hence the MSD is not sparking. My question is this, does the ecu output a ground, OR a +12v?? If its a +12v signal, the answer is as simple as a relay, however i let a friend borrow my test light and my voltmeter so SOL applies for me tonite...




Modified by FFgeoff at 2:06 AM 7/7/2003

 

Geoff,

I am not running an ignitor. What I did, or going to do is use the trigger off the autronic. I think you can do this with the EMS too. But I am running some hall effect sensors in the distributor and its completly gutted.

But I dont know what you are asking, I just thought I post.

 

The AEM has to many features, reading that link confused me. Don't know about the tack output, never messed with it. I set mine up just like the diagram. I'm running the AEM EMS, 6AL box, Blaster 3 coil and MSD cap. Sorry can't help with the output thing. Later Allen

 

so it worked for all of you EMS guys... im running a hondata, that might be the problem?

 

the white wire needs to be triggered by the ECU. (AEM, Autronic, haltech, whatever)
It needs to see a ground. If you ground it you should see spark.

Your RPM Signal for your gauge can then come from the side of the msd.

 

exactly what i am saying, it doesnt get the signal from the ecu for whatever the reason.

When you maniually ground the white wire going to the msd i get spark, but thats it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Header Tech &raquo;</TD></TR><TR><TD CLASS="quote">the white wire needs to be triggered by the ECU. (AEM, Autronic, haltech, whatever)</TD></TR></TABLE>
Where can I find info on the whatever ECU?

 

So something is wrong with the settings of your AEM Maybe?

Ecu's need to have the crank trigger/cam sync wired&setup correctly before the ignition outputs work. Im not sure about AEM because i've never used one and probably will never use one.

take a look at your aem software while your cranking and see if it gives you an rpm speed while your cranking it.

 

I was under the impression that the ECU sent a +postive signal to the ignitor to trigger it to fire...

Its still early for me, so i didnt quite understand your post entirely.

In a stock setup, the ignitor puts out an rpm pulse every time the ECU fires it,
But if im reading correctly the MSD unit wont fire until it gets an rpm pulse, which wont happen because its not firing.(?). The msd unit should be able to get a rpm
signal from the (-) side of teh coil, but thats a moot point if it wont fire in the first
place. I erally dont know what im typing, i just woke up

 

htp://www.whatever.com

 

http://www.msdignition.com/pdf/pdf24.pdf

reading that just makes me think i am on the right track but i still dont understand why its not working. I really dont think the ecu sends a +12v signal, i think it is like an injector and just adds a ground...

 

Not to jack your thread, but is it possible to run sans-ignitor without a standalone but using an MSD box?

 

thats what i am in the process of figuring out, as the hondata is the same as stock ecu.

 

From waht i understand, the MSD box requires an rpm signal before it sparks. However, the stock ignitor is what provides the rpm signal.

If its possible to use the trigger signal from the ecu as an rpm signal, then
that would work.. just some thoughts.

 

the ignitor does not provide any signals, all the ignitor is, is just a mini-MSD

a wise man tells me that an ignitor is a combination of a schmidt trigger and ignition module built into one... that may be where the problem now lies, i no longer have a schmidt trigger


Modified by FFgeoff at 5:46 PM 7/7/2003

 

The rpm signal comes from the ignitor.
Every time it gets a trigger from the ecu, it puts out an rpm pulse.

 

rioninja is on the right path, Grasshopper.

My question is, can the MSD accept TDC sensor input as RPM feed? If the MSD expects a purely digital signal, or something stronger than the one generated from a hall effect sensor, then that is where a schmidt trigger comes in so you can use Honda ECU and MSD with no ignitor.

 

Ok, I got a question for you guys about the stock ignitor. I made a post in 93LScivic's thread but I want to try and ditch the stock igniter as well..

So basically the blue wire coming off the ignitor provides the tach signal, right?
Also, there are 3 other wires connected to the igniter. The switched +12v black/yellow and 2 white/green wires. One is the trigger and one is the output. Where does the igniter get the trigger from? I guess I'll take a look at the helms manual. Just trying to clarify to myself exactly how the thing works so I can get it working as well. Thanks.

-Mike

 

The ignitor gets it's trigger input from ECU pins A21 + A22, which are red/grn wires that turn to yel/grn wires by the time they make it to the distributor.

Blk/yel is 12 volt switched ignition power.

Blu is rpm output.

wht/blu fires the coil.

The ignitor get's it's ground through it's housing + being bolted to the distributor.

Your wiring colors may well vary from the unit I have in my hand.

I'm thinking that the yel/grn input from the ECU can be ported to the MSD RPM feed in order to fool the MSD into working. No comment how that would affect your dwell time or anything like that. I know less than nothing about MSD ignitions.

 

ok some progress made.

Its clear that no matter what i do, the yel/grn wire is not going to trigger the MSD to fire. Now the question is simply, what does the AEM have that the honda ecu does not have? It clearly outputs a different signal than the honda ecu.

If there is something else (maybe MSD already makes it) that will take the signal from the yel/grn wire and input that to the MSD in a fashion that the MSD can understand we will be in business... now J davis, what is the idea of tapping into the single tooth hall effect sensor?

 

That was to try to introduce an RPM feed for the MSD, since I am inferring from others comments that the MSD needs an RPOM feed to work.

 

I have an msd. you go into the distributor and wire it there. When you talk about the "igniter", your talking about the unit to the bottom right (looking at the dis) also called the ICM or are you talking about the coil at the top? I'm not assuming your stupid either...

 

Oh, by the way, what kind of car do you have?

 

the igniter is the ICM.

mike -- i follow your post but are you running an ignitor or just running the msd off of the ignitor?

The entire problem is actaully pretty simple -- the MSD can not use the signal on the yel/grn wire to make a spark. The ignitor changes that signal and then outputs it by pulling low to the coil.

The entire problem is in the signal in the yel/grn wire and i think i need to find an oscilloscope to see what the yel/grn wire actually does.

 

The Yellow/Green wire is the input to the igniter. The source of this signal is the ECU. Don't know if it's a transistor or a logic gate. Doug at Hondata prolly knows.

Inside the MSD, a 47 ohm, 5 watt resistor connects the White wire to 12v. Switching the White wire to gound requires about 1/4 amp. Points require a minimum of 1/10 amp to keep them clean.

Our earlier units used a 2N2222 as the output transistor, which can drive the igniter with no problem, but it's too wimpy to drive the MSD White wire. Now we use a ZTX857.