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Newbie here, both to the forum and to rotaries (so bear with me).
I've recently got a August-1995 FD (JDM Import) that I'm currently working on as I have not got much spark and could really use some direction from someone with experience to help me troubleshoot more effectively.
Bit more about the car: It's a 1995 Series 6 FD (frame no. 300001-399999) but has had an S7 engine swapped into it back in Japan. They swapped in the N3F1 ECU and the EM harness. The F harness has been re-pinned into the new/different ecu connectors. Have compared all pins and they appear to be all in order.
Problem: Basically, no spark measured with an in-line spark tester, except for a tiny spark as I start cranking and no spark whatsoever as the engine cranks. This is the same across all 4 plugs/leads. And car obviously does not start (but there's definitely fuel).
What I've checked/tried:
Engine side:
✔️Measured resistance of Coils & Leads, all well within spec
✔️Ignition coil wiring sub-harness continuity all checked
✔️New spark plugs
✔️Different igniter
❓I measure about 0.2V less than battery on the Black/Red & Black/White wires going to the coils, igniter, and ignition switch.
Other
✔️Battery charged and good
✔️Tested and confirmed all relay function
✔️All fuses OK
ECU & Sensors: I've used wiring diagrams/workshop manual to validate my measurements against.
✔️No ECU fault codes (hooked up LED to B+ & FEN)
✔️CAS Measurements appear OK: Resistance of 1.23kΩ resistance between CAS NE- and G- signal (within the 0.95-1.25 kΩ spec), measured at the ECU plug.
Checked CAS voltages at the ECU pins with the ignition ON, and when cranking (to get some RPMs as I can't idle):
✔️NE+ Signal below 1.0V with Ignition ON, spikes up 0.1-0.4V when cranking
✔️G+ Signal below 1.0V with Ignition ON, spikes up 0.1-0.4V when cranking
✔️G- & NE- Constant below 1.0V
❓ All ECU Ground pins seem OK, with the ignition ON, I measure between 0.0008V and 0.04v on any of the ground pins. Not sure if there's supposed to be 0V flat or not.
❓ Trailing Rear, Trailing Front, and Leading igniter ECU pins should have 0V with the Ignition ON, whereas I measure ~0.2V. Manuals state that whilst idle it should be between 0.2-0.5V (Reference) whilst idle, I measure below 0.2V when cranking.
❓Not sure if relevant, but I have measured only 9V whilst cranking on the Ignition switch/start signal pin, whereas that should be battery voltage according to spec. I measure good battery voltage at the constant/backup pin.
Personally I am beginning to think that my ECU is just fried. I would actually like to move to a Haltech later on, but I worry that there would either still be an issue, or worst case I'd fry that ecu too.
Would really appreciate some insights or direction from someone a bit more experienced than me. Hopefully it's in the correct forum section (If not, feel free to delete or move it). Thanks for reading!
Last edited by Reitangle; Nov 8, 2024 at 01:28 AM.
Reason: Added additional info
1. ECU may be detecting some of the legacy S6 electricals and simply refusing to operate.
2. Starting with S7 (version 4 and newer), the positioning of the coils was changed, which has caused lots of issues for people. Which coil set up is in the car? People unaware of the coil position change may hook up either the coil harness or the spark plug leads in the wrong order.
Version 3 and older cars had additonal grounding on the coil harness which was dropped on the Version 4 harness.
(This happened to me for the third time, recently, even though the local shop knows of the issue, the tech on that day, did not. Worse case is that high revs you will get detention and fry your motor!)
We plugged a Version 5 ecu into a version 4 and it refused to fire. However, my version 5 car started with the version 4 ecu.
Have you got the proper wiring diagrams for both the version 3 and version 4 cars?
(search "laujesse manuals" in the search box)
Have you opened up the ecu and inspected it? Does it smell fried? Are any capacitors burst? Corrosion?
Did it ever run after that electrical re-wiring work was performed?
You can try and swap in another ECU but sounds more like a wiring or ground issue. You can also open up the ECU and look for any bad circuits.
It did! It came into the country as a driving vehicle. I didn't originally know it had the S6/S7 chassis & engine combo but did since then also translated and compared the relevant JDM wiring diagrams to check fi all wires are correctly pinned, and I believe they are. I haven't opened up the ECU itself, but I'll have a look, good idea!
In terms of grounding issues, anything you'd recommend checking first?
Originally Posted by Redbul
1. ECU may be detecting some of the legacy S6 electricals and simply refusing to operate.
2. Starting with S7 (version 4 and newer), the positioning of the coils was changed, which has caused lots of issues for people. Which coil set up is in the car? People unaware of the coil position change may hook up either the coil harness or the spark plug leads in the wrong order.
Version 3 and older cars had additonal grounding on the coil harness which was dropped on the Version 4 harness.
(This happened to me for the third time, recently, even though the local shop knows of the issue, the tech on that day, did not. Worse case is that high revs you will get detention and fry your motor!)
We plugged a Version 5 ecu into a version 4 and it refused to fire. However, my version 5 car started with the version 4 ecu.
Have you got the proper wiring diagrams for both the version 3 and version 4 cars?
(search "laujesse manuals" in the search box)
Have you opened up the ecu and inspected it? Does it smell fried? Are any capacitors burst? Corrosion?
1. Interesting thought, I would be keen to understand that a bit further. Especially since the car did run with the configuration prior. In terms of troubleshooting that, is there a potential scenario of depinning a bunch of ECU pins that are not required for ignition to work?
2. I wasn't aware of the differences. The car has the S7 (V4) coils I believe, I've also compared all of the wiring / connector pinouts related to the ECU and common (X) connectors in the 'ECU area'. Just a small snapshot of my comparison in Excel of one of the ECU connectors that shows the igniter signal pins and I do believe them to be pinned correctly to the new ECU.
Also, photo of my coils:
Have not opened up the ECU and inspected it, I'll get on that today, thanks for the suggestion! No smell though.
FYI: I have a full copy of those JDM Infini diagrams and such, I believe it's the same set as those, but I do like the fact that it's all one big file
Seems yours match this set of Version 4 coils and harness also seems to be hooked up correct. Are the leads to the plugs connected correctly. When I picked up my car about a month ago, it was running very bad. I had had them install a new coil harness. Sure enough they had hooked up the new harness in reverse order, with the white and black positions switched. Car is running better with the new harness. A write up I read in a JDM tuner magazine said you should change out the coil harness every five years (plugs leads every year).
The Japanese FSM (1995-12 WM4029) said the coils are the same with earlier versions, just the position was changed.
Thanks for confirming that @Redbul. I have the connectors to the coils connected correctly (just like your example). I'm also quite sure that the coils and leads are in good spec (measured all of it) and I get the same no spark across all of them. There is a tiny bit of spark right as I crank, and then noting, same across all of them.
I just had another finding, which I thought I had checked. But with the ignition ON, I measure about 0.2V less that battery on the B/R wire going to the coils.
Could your coil harness be bad? is there power coming from the igniter? Could be a bad ignitor (they are pretty robust).
Check the connecting wires between the ignitor and the ecu.
Check for a bent pin on the ECU.
Check if the front or engine harnesses have been damaged passing through the firewall. Sometimes when people fish wires through the same firewall opening they damage the harnesses.
My coils were showing spark, but the tech still suspected the coils spark was too weak, so we subbed in a different set. Seemed to be part of our solution.
You can pull coils sets off Buyee for $100. Also I see the Versions 4+ coil harnesses for sale on Buyee. Why not replace yours? I see used ignitors for about $100 as well.
Could your coil harness be bad? is there power coming from the igniter? Could be a bad ignitor (they are pretty robust).
Check the connecting wires between the ignitor and the ecu.
Check for a bent pin on the ECU.
Check if the front or engine harnesses have been damaged passing through the firewall. Sometimes when people fish wires through the same firewall opening they damage the harnesses.
My coils were showing spark, but the tech still suspected the coils spark was too weak, so we subbed in a different set. Seemed to be part of our solution.
You can pull coils sets off Buyee for $100. Also I see the Versions 4+ coil harnesses for sale on Buyee. Why not replace yours? I see used ignitors for about $100 as well.
I've checked the coils sub harness, check continuity on all wires, also completely retaped it, I'm certain that harness is correct.
Just check the ECU pin, looks all good!
Just checked where harness goes through the firewall, seems fine, no damage.
Happy to change the coils, that's not a problem, I can even get it locally. I have done so with the igniter as well, just to try. But I am not convinced that all three coils would have magically gone bad all at once, when I keep in mind that al measurements are well within the service manual spec. That being said, I will start looking for a set.
However, I do feel like, with the fact that some of my voltages aren't within spec, there is some sort of other wiring issue.
Originally Posted by Redbul
Replace your EGI relay. if it has been pulled too many times it may be cracked.
I'll have a look for another. But again I cannot find any issue with it. Measuring and testing it on the bench outside the car it behaves like a fully functional relay.
Originally Posted by Reitangle
I just had another finding, which I thought I had checked. But with the ignition ON, I measure about 0.2V less that battery on the B/R wire going to the coils.
Could that indicate a short, or another anomaly?
Following on from my update above, I've also now confirmed that this is not just the Black/Red wire on the coil sub-harness, but also on the Black/White wire it connects to. I measure the same slightly lower voltage at both the ignition switch, and the igniter.
Any ideas why there might be this 0.2V voltage drop?
Not that this answers your question or solves any of your issues, but 0.2 V drop should not be a reason why anything is not working. IMO, 0.2 V is not significant, so something else is going on. If 0.2 V drop was significant in ignition function, it would almost never work.
I was told, , but never verified, that somehow the Version 5 ECU would recognize a Version 4 Air conditioning system and refuse to run a version 4 car.
I don't know if something like that is going on here.
Often at a late stage, the JDM head units are removed before export.
A recent car here came in with a aftermarket security system that messed up the wiring. The car had stopped running. One guess iwas that when they pulled the radio, it messed up the wiring more. The owner pulled out all the security a stuff and patched up the wiring, but still there was no fuel flow. In the end he banged the fuel pump with his wrench. And the car started up and runs beautifully.
My suggest therefore, bang everything at least once with your wrench.
You might not appreciate that as humour, at this moment, but we are starting to get into mystery solving now..
(Check for rat activity.)
Check to see if prior owner haa a hidden kill switch.
I would caution that, although RX7Club has an almost infinite amount of useful information, Version 4+ cars have only begun to be in the US market for a few years, and info specific to them may be scarce.
Considering there were major changes for Version 4, and newer, cars, the body of information may be scarce.
Meanwhile, I would think the Australians may be well ahead of us, and there may be English language FSM kicking around there.
... In the end he banged the fuel pump with his wrench. And the car started up and runs beautifully.
My suggest therefore, bang everything at least once with your wrench...
Back when I had a TR4, the car often wouldn't start - the solution was to hit the starter solenoid with whatever tool was handy. Lots of older cars respond well to that remedy.
Not that this answers your question or solves any of your issues, but 0.2 V drop should not be a reason why anything is not working. IMO, 0.2 V is not significant, so something else is going on. If 0.2 V drop was significant in ignition function, it would almost never work.
Cheers Dave. Whilst it does necessarily say, here's what you should fix, it at least helps me more efficiently troubleshoot.
Originally Posted by Redbul
There was a MAP sensor change for Version 4 cars. If they did not replace the S6 MAP sensor, the ECU might not like the signal its getting.
You said you tested for codes and did not find any.
So it is unlikely that the car is going into "limp" mode.
In limp mode it would likely still run, just badly.
It's an entire v4/s7 engine and ecu so pretty sure the map sensor is also a v4. I have also tested the map sensor and measured voltages at the Ecu pin (and it's well within spec, per the v4 FSM), also if I disconnect it, I do get a fault code on the ECU that I can clear after reconnecting. So I think the map sens is fine.
Originally Posted by Redbul
I was told, , but never verified, that somehow the Version 5 ECU would recognize a Version 4 Air conditioning system and refuse to run a version 4 car.
I don't know if something like that is going on here.
Often at a late stage, the JDM head units are removed before export.
A recent car here came in with a aftermarket security system that messed up the wiring. The car had stopped running. One guess iwas that when they pulled the radio, it messed up the wiring more. The owner pulled out all the security a stuff and patched up the wiring, but still there was no fuel flow. In the end he banged the fuel pump with his wrench. And the car started up and runs beautifully.
My suggest therefore, bang everything at least once with your wrench.
You might not appreciate that as humour, at this moment, but we are starting to get into mystery solving now..
(Check for rat activity.)
Check to see if prior owner haa a hidden kill switch.
That's some interesting stuff that sparked (pun not intended) some thoughts. Would you have any ideas as to how the ECU/car would behave if I just depin everything related to the A/C? Note that I have measured the A/C related pins on the ECU and compared to the FSM everything's within spec and responds to the controls on the dash correctly.
Regarding the security and other wiring, there doesn't appear to be any damaged wiring under the dash, but there have been additional speaker wires run to the back and there was was a HKS Turbo timer harness (I think) in the glovebox, which does connect to the ignition sw if I am not mistaken, I don't see any issues there though. Had a look online to see if removing a turbo timer can cause issues, but no result, but definitely could be that there is something I'm missing and he problem is under the dash somewhere.
Car does have fender liners and can't see any signs of damage by critters in there.
The only other thing I can think of, is that the left rear taillight did have a short at some point, it came with modified taillights with LEDs in them that had water in them and had the unmistakable smell of shorted electronics. I have since replaced these with a fresh OEM set.
Originally Posted by Redbul
I would caution that, although RX7Club has an almost infinite amount of useful information, Version 4+ cars have only begun to be in the US market for a few years, and info specific to them may be scarce. Considering there were major changes for Version 4, and newer, cars, the body of information may be scarce. Meanwhile, I would think the Australians may be well ahead of us, and there may be English language FSM kicking around there.
Fair enough! Does make it even more impressive how many responses this thread has gotten. Truly appreciate yours and everyone's inputs, thanks!
I did post it to an Australian rotary forum but have yet to get a response
Originally Posted by Redbul
Have you checked the Crank Angle Sensors? Are they plugged in?. Is there continuity? How big is the gap to the trigger wheel?
Yeah, definitely plugged in, and measured resistance as being within spec. I noted my measurement in the first post.
Haven't checked the gap, but I'll stick a feeler gauge in there tomorrow and check, thanks!
Back when I had a TR4, the car often wouldn't start - the solution was to hit the starter solenoid with whatever tool was handy. Lots of older cars respond well to that remedy.
