I'm curious here Craig - let us know if the additional grounds seem to help any. I think what you've done/have is plenty for solid grounds. I checked mine last night and installed the rear almost identical to yours.

 

Excuse my ignorance but isn't PK20R11 the correct spark plug?

 

Alot of these cars originally came with platinum plugs, but they are old technology and while they do last much longer than regular copper plugs they are not as good or consistent for performance applications.
Most toyota guys either replace the platinum with the copper plugs and just replace them more often (like before they used platinum), or if you want extended service life and good spark alot use the Iridium plugs.
The iridiums will last as long or longer than platinum, have the good spark of coppers, and when tuning it is very difficult to foul them out unlike coppers.
Iridiums do cost considerably more than coppers but are similar to platinum prices. I only use Iridium plugs on all my builds and all my car's including the '71 so I don't have to worry about a temporary rich mixture fouling them out.

 

I've never had luck replacing the original platinum plugs the engine ran slightly off. Maybe this application is different but I'd stick with the original plugs at least temporarily otherwise you're putting in another variable into the troubleshooting pool.

 

Thank you. I’m glad you feel this will work for now but it sounds like I still must prioritize getting the rear cylinder head hook’s rearmost bolt off to get my electrical terminal connector ring under that.

I hope both of these help some.

I still need to open and inspect the internal boards of my 3rd ECU for any signs of cap failure or other obvious issues.

I’m going to re-install my 2nd ECU which was last pulled in 2019 after an igniter failure and then sent off to Tanin Auto for cap servicing. They gave it a clean bill of health although with no Supra Turbo on site they couldn’t do any final testing of it.

My concern now is if this lack of cylinder head ground could have in any way damaged the brand new spark plugs, coil packs and igniter during my one and only startup which had erratic voltage and which lead to the last CEL 14 shutdown.

Same concern for all three of my ECUs.

...

Regarding Iridium spark plugs, the long lasting benefits from an OEM approved plug is the main reason I chose them over regular copper.

These are IK20 Iridiums. Previously I had IK20 Iridium TT plugs installed without knowing that there may have been a slight difference. This time I made sure to order the non-TT versions.

 

Sounds like Rudy has it in the same spot, so it should be fine to leave if it is working. It is probably better there than on the engine hook (has to go through hook then to head and if its painted that isn't helping), are you sure the hook is the stock location?
Also have you tried to start it yet? I don't think you would have damaged anything really, it just wouldn't have the current needed to keep IGF working and the ecu happy hence the shut down which is very normal.
I suspect that if it was the issue, now that you have the wire in place it should start and run after maybe resetting the ecu. wouldn't even bother with an ecu swap unless it doesn't start up now.

 

There is only one way to install the 2JZ-GTE front and rear engine hooks, so I know they’re all set up right.

I found a little time to test again after the last changes. I threw in ECU #2 (Tanin cap serviced and inspected) just because I already had the #3 removed since last night.

—With ECU #2 (cap serviced) & brand new igniter that died in under 4min — NO START

—With ECU #2 (cap serviced) & previous 1yr old igniter that died in 1 year — GOOD IMMEDIATE START but voltage fluctuation again within a few seconds. Initial voltage held at 14.1V before beginning to fluctuate. Shut engine off. No good long term confirmation that igniter is really okay and won’t trigger a CEL 14 due to potential existing damage inside it.

I still need to test with the ECU #3 (not cap serviced) that I removed a night ago but now I am concerned that this voltage fluctuation may have something to do with the installation of the DC Power alternator and/or Big Three cables. (2023 Addendum note: It did and the DC Power Alternator had to have its original Denso voltage regulator fitted to correct that issue but I opted to install a case modified 2003+ SC430 130A alternator instead. The voltage regulator issue was not related to my IGF issues as it turned out).

I will not run the SC again until I have reinstalled the previous Toyota/Denso 100A 3-phase alternator and disconnected the extra cables.

Also replaced connector “A” that goes onto the igniter. “B” is a little harder to take off from its backing cap housing so I’ll tackle that another time.

I have another brand new OEM TT igniter on order from Driftmotion now but I may not get it for a couple of weeks.

At this moment I am most concerned about returning the charging system back to OEM/stock before proceeding.

Or at least I’ll just get the OEM alternator back in and fully disconnect the 2/0 extra charge cable and leave the huge 2/0 additional block ground in place.

 

I also may remove my battery and get a new one just to rule that out.

It is a 2018 vintage Interstate 24F model. It was fine in early November but after waiting over two months to start the car through many 30’s-40’s evenings it went completely flat with 0.0 volts and needed a weekend long trickle charge at the local Interstate store before picking it up again.

My warranty covered this and they gave it a clean bill of health but perhaps one or more cells are not healthy.

Voltage fluctuation issues (which I *did not* have in *this* way prior to installing the DC Power 180A JZ alternator and Big 3 cables) suggest to me an issue with the alternator's voltage regulator rather than an issue with the battery cells.

But maybe it’s a possibility? It seems unlikely since both starts in the last couple of days were instantaneous and strong with the recharged battery.

...

With the OEM Denso/Toyota Supra MKIV TT Auto 100A factory alternator I had no such wild voltage issues as this. I was just concerned that its at-idle amps weren't enough for the stock Lexus SC body electrical, 2JZ-GTE coil pack ignition, extra Supra TT electric aux cooling fans, Denso TT fuel pump and a couple of other minor things.

I had figured that with the higher output alternator there would be no way I'd have the recurring igniter burn out issue or a severe voltage dip down and up like a ticking clock EVERY time the right or left turn signals or hazards were flashing.

But in fact when starting up the other night the turn signal and hazard voltage dip issue remained the same as before and the voltage fluctuations were extremely bad even without activating the hazard flashers or turn signals. Further what was a brand new never activated Denso TT igniter apparently burned out within 3-4 minutes this time... which is a new record!

...

I might suspect the Big Three 2/0 cables as well but I suspect the alternator first and battery second right now.

Hopefully those grounds on the cylinder head and intake manifold actually do make a difference but it's impossible to tell with the fluctuating voltage issue at the forefront for the moment.

 

Quick update with more to follow. It was a good evening

--I removed the DC Power 180A (6-phase) alternator and re-installed my Toyota/Denso OEM Supra TT Auto 100A (3-phase) alternator
--The big 2/0 additional alternator cable with in-line 200A fuse was removed
--The big 2/0 additional engine block ground cable to battery negative was left installed
--The additional battery negative 2/0 to chassis ground cable was removed from its short run location and the connection was extended with a 2/0 butt connector (and more heat shrink tubing) with more cable and given an eyelet connection at the chassis sub-floor at the base rear of the shock tower. Connected to it is my intake manifold additional direct ground wire.

Still installed in the car: 2JZ-GTE ECU #2 (Tanin capacitor serviced) & the igniter which I thought had gone bad in early November 2020.

The SC started right up. NO voltage fluttering and fluctuation!!!

The voltmeter started at 14.0-14.1V and settled to around 13.5V and later 13.2-13.4V

I let the engine warm up and as it did I started loading on accessory functions: A/C (which triggers on all three additional electric fans), fog lights, radio and turn signals

Even as the engine warmed up to temperature the volts held at about 13.1V to 13.2V

Earlier in the day I had checked the terminals and continuity of all my turn signal connectors and their chassis ground points. Everything checked out. I still got the slight rhythmic voltage dip any time the signals were activated but even if the idle seemed to be affected slightly by this there seemed to be no adverse issue.

Because I was concerned that this igniter might have some damage and thus could potentially go out on me on a test drive at night I got the SC's tires rolling and brakes engaged a bit just in my driveway. At no time did the engine hiccup and at no time did I get a CEL 14.

The additional two factory cooling fans are a bit louder but the seem to really to their job well! Not bad for just under 18 Amps of current draw for all three combined!

...

Whenever the next TT igniter unit comes in the mail I'll be a little more at ease because at this point I do not like to be without a fresh spare in the trunk but overall I'm relieved. Everything seems to work well now and all my revised additional circuits are doing what they should

Ali, I think you hit the nail on the head. This current igniter might be okay or it may have been harmed a little (hopefully not) but if I never had another igniter unit go out on me again then I think this will prove that the missing cylinder head ground wire to chassis was the culprit after all. Once I get the SC out again and drive it for a while we'll see.

But since that was definitely a huge mistake omission on my part it is certainly possible, isn't it?

...

The weirdly random voltage fluctuation I strongly feel is related to the new DC Power alternator having some issue. I am going to take it into my local Autozone to have them test it and I will contact DC Power to see what they say. But for the time being I am just going to leave the factory TT Auto 100A OEM alternator installed. It seems to do fine again for now.

Maybe a physically modified SC430 6-phase 130A alternator is in my future.

Anyway the next big project will be the big turbo replacement job once I order a few more special tools to do it with

...

Note on the HIDs:

My HIDs still seem to work just fine but I think I will consider what LED options are available today. The same for the fog lamps and, since I still need to test Lexus2000's Camry Gen5 replacement flasher prototype that is LED capable, perhaps I can ultimately alleviate the big turn signal current draw dip with LEDs all around.

I recently found this thread in which Gerry talks about the SC signal flasher circuit in relation to this issue and he hypothesized it might have to do with something going wrong with the flasher unit itself:

https://www.clublexus.com/forums/sc-...ker-is-on.html

I think since most SC300/400 owners who do not have heavy modifications usually don't install voltmeters the exact amount of voltage dip isn't ever noted... just the slight dimming of headlights and interior lights on each blink. FWIW my HIDs never dim when my turn signals are on.

....

I'm just really happy right now that the SC is purring along again

 

Honestly with all my wiring shenanigans I have personally never burned out an ignitor, which leads me to think it is pretty hard to do. normally speaking.
I think alot of those issues stem back to the missing dedicated cylinder head ground, and possibly the aftermarket alternator as per your trial and error there.
I personally avoid aftermarket alternators, I would retrofit a newer tundra alternator before getting an aftermarket, or even another junkyard oem toyota alternator.
Even with all the described extra accessories in your car, I don't think you will have an issue with the stocker and def not with the tundra one.
Unless you are constantly draining batteries, if it ain't broke...

 

I feel dumb for not suggesting to check the head/intake manifold grounds. I've seen so many times after people have done an engine swap where they forgot to bolt the wire to the intake, engine ran terrible or not at all. Also have seen where the lug corroded same issue, engine runs poorly or not at all.

For LEDs check out this chart I'm using the 3rd one down it's great especially for the price. WORKS PROPERLY in a reflector housing no glare no blinding people has a perfect beam pattern.
https://bulbfacts.com/led-kits/recommended/

 

I think you're right Ali. Everyone with experience using these engines whom I've talked to has said the same thing: that it's very hard to kill a Toyota igniter. And that's what has driven me nuts trying to solve this problem because in my experience so far with a GTE engine it's been extremely easy to kill them

I have been cautioned time and again to check my ground connections and I did but never realized I might be missing a critical one. I never had this issue with my stock 2JZ-GE and its igniter but that engine was assembled and installed at the factory in Japan when the car was built.

I've heard of ignition coils going bad with a shorted secondary winding but it's still exceedingly rare with these cars/engines. As you say... you really have to try hard to damage them or the igniter.

I agree with you at this point regarding aftermarket alternators. I'll get the DC Power alt checked out but I am sticking with the OEM 100A older factory design at this point. I might try the Tundra alternator or the revised SC430 alternator which is basically the same 130A and 6-phase but it has the oval connector we use.

I thought I needed more idle amperage but apparently I don't(?) I know I did not actually need anywhere near the 180 amps of the DC Power.

No, no. I'm the one who should have more thoroughly checked the factory ground diagrams and stock engine bay reference pictures. Since the day I started the new engine until I finally added cylinder head grounds nearly four years later that one completely escaped me and seeing how simple a thing it was all along I feel foolish.

You and Ali have hit the nail on the head. I do feel that catching this can explain more than one quirk I was observing over the last few years.

Thankfully other than some dings, chips and gently fading paint requiring periodic cosmetic maintenance by me this SC body is very clean and has no issues with any rusted or corroded grounds. Other than some grime buildup here and there that I didn't catch all my wires and connections have been well protected.

I will check out that link for the LED kits, thank you! I still feel my HID kit is in good shape and not causing any issues but I need to be aware of more modern alternatives just in case.

Aside, as to the rhythmic voltage dip when using my SC's turn signals, I think maybe that's common and normal at this point? Every chassis ground connection to those bulb receptacles was clean looking and gave a solid continuity signal on my multimeter. Perhaps it has to do with the 3-phase alternator's idle output or just the total current draw from all those bulbs on one side or both sides every time the OEM relay makes it click.

Given that, I'm going to call it normal at this point and not be concerned when testing your prototype relay.

 

Sounds like you got this figured out Craig! You're so thorough, I'm always impressed. Sounds like you've got an alternator that isn't up to snuff or simply doesn't mesh with our electrical system. I'll be curious to hear what DC says about it.

 

My ES does it and it has only 2 signal bulbs per side so yes it's normal the voltage regulator can't compensate fast enough. You'd think the battery would smooth this out? I did notice when I put in a fresh battery a few years ago it became much better. BTW the 3rd generation ES (mine) has a pulsating voltage problem anytime the engine is running the dome light especially shows it. A 130 amp alternator helps (stock is 80, too small) but doesn't cure it. I'd love to run a lithium/ion battery but they don't do well in cold weather.
If you go all LED you won't see it anymore since pretty much all LEDs now have an internal regulator/driver circuit. BTW I have a modded Camry flasher in my winter beater it works perfectly no issues.
HIDs are nice but the ballasts and wiring make the whole thing bulky. I feel like LED tech is finally at the point where they are a viable replacement for xenon bulbs.

 

I think alot of people miss it because it isn't part of the main engine harness. It is probably still attached to the GE engine at Gerrb's place lol.. maybe he will send it back to you
I have a spare GE engine I picked up from a 94 na supra in the garage, it still has the ground wire attached to the rear of the cylinder head so hopefully that guy figured it out also.

As long as you aren't doing only short drives it should be fine. If the car is sitting for a long time put a tender on it or just charge it back up before you try and crank it so you have less chance of damaging the cells.
These cars have more of a battery drain issue especially in winter versus a charging issue. I am pretty sure the small V fluctuations you are describing are normal.