[capnjck]

Hello everyone, I have a 1996 Suzuki Sidekick JX Sport, with the 1.8L Engine. A bit ago, I had a misfire on cylinders 1 and 3, and diagnosed the cause as being the Coil On Plug's for those 2 cylinders. I had replaced them about 4 months ago now. I now have a misfire on cylinder 4, which I have diagnosed to the coil as well. I had picked up 4 coils from a Vitara from Pick and Pull right after replacing the 2 noted above. Today I went to install the other 2 coils to find that the 96 1.8l has a 2 wire COP, while the Vitara coils are 3 wire coils.

I looked into the wiring diagrams for the 96 Sidekick, as well as the 2000 Vitara, and the only thing I see as different is the Vitara coils include the igniter, while the Sidekick has a separate igniter that handles all 4 COP's. If I am correct, as long as the voltage/current required to fire the igniter built in with the 3 wire COP, is the same or lower then the voltage/current required to fire the igniter that originally came with the sidekick, then it should not adversely effect the ECU.

So my main question would be if this would be possible? If I bring the lines from the ECU that lead to the original Igniter, directly to the 3 wire COP's, and make a ground for them, would there be any issues? Does anyone have information regarding the specifications for the coils and/or igniters that would help determine whether or not the ECU will be able to drive them without damage?

I am attaching the wiring diagrams for both vehicle's COP/Igniter to ECU circuits. I am still working to develop a test I could do to determine voltage/current required to fire the igniters, if anyone has any information or ideas on that, it would be helpful as well. I have Analog and Digital Oscilloscope's, as well as a 200Mhz Logic Analyzer. Thank you all for your time and help. Have a great rest of your day, and stay safe!


This image is the wiring diagram for the 1996 Suzuki Sidekick Sport 1.8L Ignition System.

This image is of the 2000 Suzuki Vitara JX 2.0L Ignition System

 

[fordem]

In theory it might work, I would want to compare the drive wave forms coming out of the ECU - you have the 1.8,I have the 2.0 - I'll try to get you wave forms sometime this weekend.

 

[2013GV]

The other thing to consider is drive current able to be sunk by the ecm. The 1.8 uses an igniter module to interface the low current switching transistors in the ecm to the high current supplies required by the coils.

The 2.0 has this driver stage built into the coils. You will need to scope the drive waveform on the 2.0 cop's and on the ignition module and compare the voltage spikes on the waveform. These can get up into quite high figures. I have my doubts that the 1.8 ecm will be able to run the cop setup without an interface module as the transistors in the ecm probably won't be able to handle the back emf spikes and that will be what kills them.

You could however possibly run the cop off the existing igniter module.

 

[capnjck]

That was another question I had, and forgot to bring up, since the Igniter module on the 1.8L is just a set of what appear to be NPN BJT's, at least that is what I had gathered from the wiring diagrams above, is why couldnt the Igniter drive them, since it is just 12V the igniter is feeding anyway? Another thought I had was making a separate driver for the new coils, running from the igniter or directly from the ECU, with a filtering circuit to block any spikes from residual current after the spark.

 

[2013GV]

There's a bit more to it than just voltage. I've put a link to a video that describes the ignition waveform
You need to switch some significant current, and deal with some reasonable spikes even at the "input" side to a cop unit. Not uncommon to see a hundred volts or more on the trigger line when it switches.
The existing ignitier may drive them, but I can't guarantee it.

 

[capnjck]

I am sorry about the delay in responding. I am about to scope the input of the igniter on my sidekick sport, but earlier was watching the weekly waveform #11 video regarding smart COP's, and when he was measuring the input from the ECU to the transistor/built in igniter on the COP, there was no high voltage spike, nothing was going back to the ECU, it appears as if the falling edge of the square wave had gone below 0v, down to about -2.5v, but that should not be an issue for the ECU.

I had just completed capturing the waveform for Cylinder 1, on the ECU side of the igniter. There is no voltage spike, and sits at a maximum of about +3.9v. I am uploading a video to youtube right now of how I took the measurement, and the details of the waveform.

In regards to the 1996 sidekick sport, the external igniter input is not seeing any voltage spike. It is possible that the COP's from the 2000 vitara, being as close as they are to the secondary windings in the COP, that the EMF might cause some indictive kickback to the signal line from the ECU, but I dont think there will be.

@2013GV in the video you had linked, that was regarding a distributor system, and although it had some good information in it, the weekly waveform video #11 I think is more relevant to this situation, In the #11 video, he had measured the ECU side of the COP, which had a built in igniter, and there were no large voltage spikes at all. It appeared as if there was a dip to -2.5v on the trailing edge of the drive signal, but that shouldnt be an issue with frying the ECU.

@fordem Please let me know when you are able to pull the waveform for the ECU side of the COP for the 2000 Vitara. I am attaching my video to the bottom of this post.

I do apologize in advance for the video quality, also the only really useful scope I have is an Agilent/HP 1662AS, so I had to take pictures from my phone. I cant at the moment buy new coils, let alone a better oscilloscope

Entire waveform with markers for both time and voltage:

Falling edge of waveform zoomed in on the time axis

Video: Video of measuring the waveform.

 

[aquanaut20]

I think you are confusing the primary signals to fire the COP, to see the secondary (high spike, Kv) you need to use a HT wire from the COP to the plug.

 

[capnjck]

@aquanaut20 I am definitely no professional when it comes to automotive, but I am curious what the secondary side of the coil has to do with driving a 3-wire COP from the ECU? I understand that if the secondary winding is at a lower ratio of windings, that it wont create a high enough voltage. Since the 2000 Vitara uses the same spark plugs, and is essentially the same engine, just a slightly higher displacement, that the COP's would be able to drive the 1.8L engine.

If I am missing anything, please let me know, again I am no professional when it comes to automotive. Again my main goal is to replace the 1996 1.8L 2-wire COP's with the 3-wire COP's from the 2000 Vitara. From my understanding, I just need to make sure that the ECU is able to drive the igniter located within the 3-wire COP's, which from what I gathered last night, the 1996 ECU is outputting a roughly 5v signal to drive its igniter, and as long as the 3-wire COP's use 5v to drive as well, and do not have a large voltage spike/inductive kick going back to the ECU, then it should be able to drive them.

This does not take into account the amount of current required to drive the 3-wire COP igniter, I do not have a current clamp that I can use on my oscilloscope, but do have one for a MacTools Multimeter, I will try to see what amount of current the ECU uses to drive the current igniter today. If need be, I can try to build a AC/DC Current clamp for use with my oscilloscope.