No Spark

[Augster]

After putting in new 95+ style injectors and using a JWT adapter kit with pigtails, car won't start.

It was sitting for almost a year with the plenum pulled (got sidetracked in whole-house remodel). I took it apart because it wouldn't idle worth a damn, always dying.

After reassembly, everything was back the way it was a year ago, with no other changes than the injectors and new pigtails. There's fresh, wet fuel on the plugs. There's 12V on center wire of all accessible coils, and ~1.2-1.5 Ohms between center and left wire (as seen from fender side). Ignition coil relay is engages when 12V is applied across pins 1 and 2 with ~1.5 Ohms across pins 3 and 5. But there is no noticeable spark arcing between electrodes with coil/plug pulled and metal body of plug touched to ground. Coil connectors have locking tabs broken off, but they are firmly seated onto coils with electrical contact cleaner applied.

Really not sure what else to check.

Car has only 82,000 miles with plugs, coils, and timing belt replaced around the 75,000 mark, which was like 10 years ago (don't drive it much).

1991 MT TT, original engine.

[Augster]

I found out how to properly measure the coil resistances and got 0.9 Ohms on all coils. Not sure if that 0.2 ohm difference is enough to prevent any of the coils from firing. But $600 for brand new coils is a bit of coin so I hope it's something else...

[NolimitZ32]

Its pretty rare for all coils to drop at once, have you tested your PTU and CAS? Have a look at the FSM troubleshooting procedures, also if you have a Phase 2 PTU the testing procedure can be found in the sticky on the top of the tech forum. If you don't have a phase 2 PTu I would be willing to bet that is where your problem is. Also if the car sat for a year was there a chance that some pesky rodents made their way into the wiring looms and had a feast, its rare but also happens.

[Augster]

Found a site that shows troubleshooting steps for non-firing spark plugs:

(LINK TO COMPETING FORUM REMOVED)

Got to the PTU testing, and if I followed the diagram accurately:



Conditions fail for terminal 1 (labeled "E1" on plastic PTU body) positive and terminal 2 (labeled "E2") negative (did not get infinite resistance, but got 170 Ohms), and for terminal 3 (labeled "E3") negative and terminal 1 positive (did not get infinite resistance, but got 322 Ohms). Tested with a barely used 2-year old Fluke 87V Digital Multimeter.

Since this sucker is almost $200 shipped, did I test the PTU correctly as specified in the image above? I have the dealer-recalled v2 PTU install (black plastic body with sub-harness).

[Augster]

Its pretty rare for all coils to drop at once...

Agreed, so I'm doubtful it's the coils, but can't completely rule them out

...have you tested your PTU and CAS? Have a look at the FSM troubleshooting procedures, also if you have a Phase 2 PTU the testing procedure can be found in the sticky on the top of the tech forum.

I just tested the PTU from a set of procedures I found prior to your post, and it "seems" bad if I'm following the steps correctly and not getting the specified results, assuming those procedures are for the v2 PTU.

I'm not familiar with the "FSM troubleshooting procedures;" can you provide clarification and/or links?

Regarding the tech forum, I initially tried that in the early stages of my troubleshooting but the link brings me to an empty page. If there's something more that I'm missing, then that page is not designed very well to easily find the links in question. EDIT: I clicked on the wrong link (Tech Pages), and only just now saw the lower row of links and the one you mentioned (300ZXZ (Z32) Technical), and there in the stickies area was the S2 PTU test procedures, which is the same that I found elsewhere.

And I do have the dealer-recalled-and-installed black plastic-body PTU v2 with sub-harness. I'm the original owner and remember having to bring it in way back when...

Also if the car sat for a year was there a chance that some pesky rodents made their way into the wiring looms and had a feast, its rare but also happens.

Always a possibility, but I don't think that's the case in my situation as there's nothing I could find indicating any "eaten" wiring and all other electrical systems seem operable; just no spark.

[NolimitZ32]

Augster, the information you posted is available on this site in Dead Cylinder? Can't figure out why? Read Me! (S2 PTU Test) I have removed your link to a competing forum (as this is a borderline violation of forum rules). The Factory Service Manual contains a section on troubleshooting of systems, you will find pretty much anything you could ever want in there. Also if you are getting reading which are way off and you've tested and retested it is extremely likely that it truly is a bad part and not your testing skills.

[Augster]

Augster, the information you posted is available on this site in Dead Cylinder? Can't figure out why? Read Me! (S2 PTU Test) ... Also if you are getting reading which are way off and you've tested and retested it is extremely likely that it truly is a bad part and not your testing skills.

I'm questioning if I'm following the PTU test procedures correctly, because it's rather cryptic. I initially tested it assuming the 6-pin side labeled E1 through E6 were the terminals to test for via the diagram, but after doing more research, I believe those 6-pins each correspond to the 6 different coils and thus are PTU output signals for each coil. So connecting a multimeter to the different coil output terminals doesn't make sense as far as how they could possibly be electrically connected.

So then I reorientated myself to the diagram and assumed that "terminal (1)" meant any of the E1 through E6 terminals on the PTU (labeled "1" through "6" in the diagram), "terminal (2)" meant any I1 through I6 terminals on the PTU (labeled "a" through "c", and "e" through "g" on the diagram), and "terminal (3)" corresponding to G terminal on PTU (labeled "d" on diagram). From that perspective, the testing means I could pick any E1 through E6 PTU terminal to represent "terminal (1)", any I1 through I6 PTU terminal to represent "terminal (2)", and G PTU terminal to represent "terminal (3)". I tried every possible combination which involved "terminal (1)" and "terminal (2)" and sometimes they match the table, and sometimes they don't, depending on which E1-E6 and I1-I6 terminal I test.

Since either way I test the PTU, it fails in some way. So did I come to the right conclusion that the PTU is defective, wondering in my mind how the PTU could fail by simply sitting inactive for a year?

[NolimitZ32]

I really don;t know how it could fail by just sitting. As for your results, you are right, its pretty cryptic indeed, I did this a long time ago and forgot how cryptic (you picked the best word for it) the procedure was. I haven't gone through the FSM troubleshooting section in a while but there should be testing procedures for issues matching your condition which involve other components besides the PTU. I just though about something, are you sure you plugged the COPs in correctly as in the correct plugs to the correct COP? I know its far fetched but I'm just throwing it out there.

[Augster]

I really don;t know how it could fail by just sitting. As for your results, you are right, its pretty cryptic indeed, I did this a long time ago and forgot how cryptic (you picked the best word for it) the procedure was. I haven't gone through the FSM troubleshooting section in a while but there should be testing procedures for issues matching your condition which involve other components besides the PTU. I just though about something, are you sure you plugged the COPs in correctly as in the correct plugs to the correct COP? I know its far fetched but I'm just throwing it out there.

Eh, "COP"???

Regarding troubleshooting, as I originally posted, after pulling out two different coil/plug combinations and grounding them, I did not notice sparks. And the plugs were both wet and smelled overwhelming of fuel. I then checked for resistances and voltages at the coil connectors as well as resistances of the coils themselves and they all seemed to be within tolerances. I then checked the ignition coil relay, both with it in the car (it clicked when car was attempted to be started) as well as off the car and it passed functionally. I then proceeded to the PTU and this is where I got stumped on that dang diagram...

But I think I finally figured it out. E1 through E6 are the "external" (output) signals from the PTU, while I1 through I6 are the "input" signals to the PTU (I assume from the ECU). I1 is electrically connected to only E1, I2 to only E2, and so forth. From that logical, I then applied the diagram testing algorithm: if either "terminal (1)" or "terminal (2)" is to be tested in conjunction with "terminal (3)" (labeled G on PTU), then simply test each and every pin to G. If "terminal (1)" is to be tested in conjunction with "terminal (2)" then only test the matched pairs of input/external, e.g. I1 with only E1, through all matched pairs.

Following this new methodology, my PTU passed completely.

Meaning, I can now go forward and check other systems...

[NolimitZ32]

Coil on Plug (ignition coil) sorry I'm just used to the tech jargon. And that sounds about right. From here I can only think of either rodents or ECU issues. And after sitting for a year rodents are definitely a possibility. Honestly I'm pretty stumped, it sounds like you've checked everything that would cause it to not start, all other sensors are ancillary to the car actually running so in theory with good COPs, good PTU, good injectors and good ECU the car should at least start and idle (even if it is like crap), I've got to be missing something, I'll think about it a bit more.

[Augster]

FIXED IT!

Once I was finally able to move past the PTU as the culprit, I started testing the PTU wiring. PTU "E" connectors tested good to the coil connectors, then I tested the ground wire: no continuity whatsoever. Disconnected the sub-harness from the original harness and a puff of white corrosion dust greeted me, with all male spades of the sub-harness caked in corrosion; blowing it out with an air gun created a big white dust cloud! Testing the original connector's ground wire I got good continuity, so now the sub-harness became suspect number one.

Scrubbed the spades with a wire brush, did what I could with the female receptacles on the original connector, blew the remaining dust out and hit with electrical contact cleaner. Put it all back together and go good continuity with only a couple ohms of resistance. Reassembled everything and the car fired up the first crank!

Now there's a misfire (single, it seems) but I can hunt that down. Even with that misfire, the car runs LOADS better than when I took it apart when it couldn't maintain any idle whatsoever.

I do appreciate your time in giving me some advice. Forum moderators and helpful members certainly can be unsung heroes, so I tip my hat for your assist!

[NolimitZ32]

Sometimes it the simplest things, and my pleasure, I do what I can.

[Augster]

It's a misfire with only cylinder 1, but I'm done for the day as I'm heading out for the night.

Not sure if it's ignition or fuel, but that will keep until tomorrow! At least I was able to finally drive it around the block after a year of sitting.

[NolimitZ32]

I know the feeling, good luck.

[Augster]

Just a closing comment on the status:

Started the troubleshooting steps as to why #1 was misfiring, so I started with the assumption that it had to do with wiring. Tested the "I" side of the sub-harness and got good continuity across the connectors to the original harness. I pulled it open and the contacts where in excellent condition, with the brass-ish color still quite prominent and no white corrosive powder residue at all, unlike the coil side of the sub-harness connection. Hmm. I then pulled the ECU from the passenger footwell and tested the #1 wire and got continuity all the way to the PTU input connector. Hrmph. I sprayed electrical contact cleaner on all the PTU connections and the sub-harness to original harness ECU connector before buttoning up everything again. I also went ahead and swapped #1 and #3 coils since I didn't noticeably see any issues with the #1 PTU wiring to ECU, just to ensure this was not a coil issue.

Fired up and no more mis-fires! I think just uncoupling the PTU-ECU connectors and using electrical contact cleaner was enough to re-establish good connectivity to stop the #1 misfire. I really can't wait to replace the EFI wiring harness so prevent any future electrical issues and perhaps to resolve any lurking existing issues.

So all is good.. except for a slight oscillating surging on idle. But one step closer to a perfect, smooth running Z!

[NolimitZ32]

Congrats man, chasing electrical gremlins is always the biggest PITA, glad you're well on your way to having her purring.

[iPhilz]

I am having the same issue with my 90Z. My coils test good and e1 thru e6 test good and show normal voltage except for e2 which shows 0.24v. I also checked the coil connections and all show 12v on the first wire but 0v on the second wire and the ground is also showing good. I checked my friend connections to see what difference there is and on his there was 10v where there was 0v on mines does anyone have an idea or lead as to what this can be?