No Spark Issue - This is the strangest behavior I've seen

[Jonnymkiii]

Due to the bizarre behavior of this problem, the explanation of what I did that led to the ignition breaking is a bit long. The jist is, I'm not getting spark at the coil pack. If you don't want to read the long story, I highlighted a few key points in blue and you can scroll to the bottom for the final problem description. Any help would be greatly appreciated.


I recently changed my CPS because my old one was leaking oil. Over Easter weekend I installed the new CPS, got it started, set the timing, etc.

I then buttoned everything up and then decided to do a couple other things while in the engine. The coil pack ground wire was stretching across the cam valley and connected to the bolt stud on the other side, so I decided to move it so it wasn't in the way. I moved it and verified it was a good ground with a volt meter. I also had to fix my FPR lines as the shop I took my car to last somehow created a fuel leak that wasn't there before (That's another story). Anyhoo, so I re-did the fuel lines leading to the FPR and fuel rail and thought I was done. I attempted to start the car, and it wouldn't start.

At this point I wasn't sure what broke it. I checked the fuel system, and fuel was being delivered. I moved back the coil pack ground wire to the location it was at before. I then checked the igniter (per TSM), and that appeared to be ok. I then noticed that only one of the coil sets were creating spark. I checked the packs per the TSM and they appears to be ok. I decided to put back in my old CPS, but that didn't help either.

A friend of mine is a Toyota mechanic, so I called him up and he came out this weekend to have a look. He checked everything as well, and couldn't find a problem. We took the coil pack out and we undid all the connectors, then reinstalled it, and the car started. We found that very odd and were both troubled we didn't find a smoking gun.

*** This is where I broke the ignition ***
I put in the new CPS again, car still started and I set the timing, buttoned everything back up, and the car still started. I then decided to relocate the coil pack ground wire again. Looking at the engine from the front of the car, I grounded the wire to one of the big screws for the cam cover, as this moved the wire out of the way of everything else. I verified the ground was good, then attempted to start the car. It wouldn't start, and the symptoms were just like before. Evidently, this is what broke it before. I moved the wire back to where it was before (Stretching across the cam valley to the bolt stud on the cam cover) and it still wouldn't start - no spark.

This makes absolutely no sense to me. How can moving the coil ground to another location make any difference as long as it's a good ground? I haven't been able to determine if any of the coils is sparking as I don't have anyone to crank the car while I look for spark, but I will say at least two of the coil pairs are not generating spark.

Anyone ever see this before?

 

[jetjock]

One needs to be careful concerning cause and effect. The root cause of your problem has to be located elsewhere. For example whenever you check a coil pack primary winding be sure to also check for shorting to the core as per the TRSM. Don't use body ground for this, use a mounting screw. Even better is to remove the screw and measure the core itself.

As an electrical guy I'll tell you what I know:

The wire is a drain for the coil pack's laminated cores, each of which is connected to the bracket and to each other by their respective mountings screws. It's there because the coil mounting plate is normally isolated from the valve covers. That said if the mounting nuts are over torqued this isolation will be compromised.

The plate "needs" grounding to prevent inductive cross talk between cores, eddy currents in the plate, and other forms of spurious induction from getting back into the electrical system. You can easily measure this noise (it's dependent on rpm) if the plate is floating. I've seen as much as 25 volts @ 300 cps and upwards of 1 amp @ 2500 rpm.

However, using an ignition scope I've never seen it effect anything ignition related. All I can say for sure is the drain isn't part of the primary circuit and technically it doesn't make electrical sense that it alone would prevent primary operation. Even if it did both of the points you connected it to are grounded. Do not connect it to the valve covers themselves as there can be significant resistance between them and the head due to the gaskets and grommets. Which of course is why the drain is there to begin with and why it's connected to the head.

I know of many engines that run fine without the wire and I've started and run mine the same way many times. Course, it's possible no connection may have an effect in combination with some another problem in the ignition system but in and by itself the wire should not. Myself, I keep it connected. After all, Toyota put it there for a reason and after seeing the noise induced by not having it I understand why.

The bottom line is loss of the ground shouldn't prevent ignition if everything else in the system is up to snuff. Because of the hash it creates a loss of bonding to the mounting plate may cause other problems in the electrical system. It would depend on several factors. My advice is to leave it connected. A bullet style connector can be installed in the wire to facilitate removing the packs when needed.

As an aside the passenger side ground wire from the head to the firewall is important. I suggest running it to an O2 sensor mounting stud rather than the head. I also recommend improving the igniter and ECU grounding.

Btw my compliments on the quality of your post. It'd be nice if everyone made such an effort.

 

[Jonnymkiii]

Jet, Thanks for the compliment and also your post. I certainly don't disagree that the root cause for this issue is something else.. I do find it odd that I broke something in the ignition system by simply moving that ground wire. I do recall the car running without it in the past, but as you said, it's there for a reason, so I leave it connected.

I will check my grounding points and I may have to investigate the harness more to make sure I'm not shorting anything in the wires leading to the coil pack. This has been very vexing and it has me and a certified Toyota mechanic scratching our heads.

I've been threatening to drive the car into a lake due to all the grief she's given me over the years.. jokes on me now since I can't even start it - I'm crying and laughing at the same time.

 

[Jonnymkiii]

I have an update that may help y'all help me.

Only one of the coil cores is getting spark (from left to right, the third one), and the first two coil cores are not. I've also recently replaced the igniter, and it didn't change the spark issue I am having. Any suggestions? Thanks in advance!

 

[jetjock]

Be sure the igniter case is well grounded. Check that all coils are receiving 12 volts referenced to the intake manifold when the key is on. Then put a test light across each of the primaries and see if it flashes when the engine is cranked. You can remove the CPS and spin it by hand to make things easier. Mark it beforehand so you won't need to later set the engine to TDC and don't turn the engine over with the CPS out.