Please help, NB8A Crank but no spark

[Mr Starlet]

Hi all

I'm getting pretty close to being stumped while trying to troubleshoot an Aussie delivered NB8A. All the sudden won't start after finished shopping. General check looks ok...

- fuel to the injector is ok
- crank but no fire
- no spark on plugs; checked lead and plugs, they're fine
- swapped known working coil, still no spark
- swapped / checked against working CAM and Crank sensors, not them either
- disconnected battery, wait, reconnect, tried, still no spark
- checked ECU circuitry for visible sign of damage, burnt, dry joint etc, but no visible issue found.

I've been told the ECU on the NB controls the coils directly as oppose to through an Igniter on the NA, if this isn't the case is there an ignitor or equivalent somewhere I should be looking for?

Otherwise I'm starting to think maybe the stock immobiliser playing up, though it's never played up in this way before. Anything else I've missed?

Any pointers would be much appreciated.

Cheers
Minh

[93_Clubman]

Minh, did it eventually start much later that day or the next day, or will it still not start?

Patrick covered a lot of ground in the following, so it might give you a lead or two as it also contains a few links to other threads of interest:
viewtopic.php?f=29&t=47266

[Mr Starlet]

Minh, did it eventually start much later that day or the next day, or will it still not start?

Patrick covered a lot of ground in the following, so it might give you a lead or two as it also contains a few links to other threads of interest:
viewtopic.php?f=29&t=47266

It went from normal driving to no firing at all, no previous dying symptom. It did start first time at the carpark then struggle and dies, we haven't been able to get to fire since.

Also not timing belt, we can see CAM moving on crank.

Just check EGI Relay, and that's working fine.

Could it be an ECU issue? or an ambiguous sensor failure causing ECU to prevent spark?

[93_Clubman]

From memory NB ECUs have been reliable, however NA ECUs less so more recently.

Have you checked all earth points?

[Mr Starlet]

UPDATE:

- Cranks but no spark (not even weak, zip all) also no fuel spray from injectors (even though fuel rail is pressurised)

Starting to think either ECU or factory immobiliser issue?

Anyone with a spare aussie NB8A ECU and is brave enough to lend for the afternoon to test?

[Mr Starlet]

From memory NB ECUs have been reliable, however NA ECUs less so more recently.

Have you checked all earth points?

Checked engine bay GND points, all seems fine.
This is a stock block female dríven NB with no engine work or any other mods done.

The fact it runs flawless for years and all the sudden, no injection or spark seems to suggest some sort of electronics control issue.
It has a factory Mazda alarm system, arming and disarming still works fine.

Does NB8A have transponder in key? Could it be a key/ transponder programming lost causing immobilisation issue?

[bigdog]

EGI relay - did you pull it out to check it? Almost guarantee that will be the problem, it's relatively common.

[Mr Starlet]

EGI relay - did you pull it out to check it? Almost guarantee that will be the problem, it's relatively common.

Yep, I've even disassemble it bare to see the relay latching also checked latch contact point for carbon build up (it's clean), also tried hardwiring the relay terminal, when activated I can hear buzz / humming sounds in engine bay.

[93_Clubman]

I've been told the ECU on the NB controls the coils directly as oppose to through an Igniter on the NA, if this isn't the case is there an ignitor or equivalent somewhere I should be looking for?

Yeah, NA6 had a separate igniter, but NA8 was different - believe NB8A was similar to NA8 in this regard.

It has a factory Mazda alarm system, arming and disarming still works fine.

Does NB8A have transponder in key? Could it be a key/ transponder programming lost causing immobilisation issue?

Don't know much about the NB immobiliser, but if you believe it's arming & disarming ok then don't think this would be the problem.

[Mr Starlet]

Interesting reference after digging up some info on NB transponder and immobiliser, describe very similar symptom to what I'm experiencing, strengthen even more after noticing the red key light (top right corner of dashboard) flashing 3 times, which according to the below is a sign of not recognising key...

http://www.mazdabg.com/ftp-uploads/MAZD ... 007_en.pdf

Immobilizer Module Variants
• Depending on the respective MIS generation the immobilizer module features various
functions:
– The first MIS generation uses a “Temic” immobilizer module (since model year
1995): - Engine is shut off two seconds after the start if a malfunction has been
detected during the verification of ID-number and / or code word.
– The second MIS generation uses a “Lucas” or “Mitsubishi” immobilizer module (since
model year 1997): - Its operation is as per the first generation but in case of an
immobilizer malfunction the engine start is prevented after three starting attempts.
Thereafter the engine is just cranked but not started.
Since 1998 a random code encryption of the ID-number transfer between
transponder and immobilizer module has been adopted for all MIS.
– The third MIS generation uses a “Lucas” or “Mitsubishi” module (since model year
2000) – its operation is as per the second generation but in addition it generally
prevents starter operation when using an unregistered key or when a system
malfunction has been detected. Moreover, the verification process already starts
when the ignition key is inserted.

Security Light
• The security light is used to indicate system activation (only on PATS) as well as
malfunctions.
• The system activation is displayed by a constant flashing light, while malfunctions are
indicated by specific flashing patterns or constant illumination.
• The current Mazda vehicles with immobilizer system have the security light located in the
IC.
• The security light is powered by the IC and controlled by the respective immobilizer
control module on the ground side.
• On the MIS the code word is entered with the aid of the security light.

[93_Clubman]

From my limited reading on NB immobilisers the biggest issue is when the arming/ disarming device battery goes.

[Mr Starlet]

SOLVED!! It's bad key, found a spare key that came with the car and it's now running as per normal, strange how a key can go bad after some shopping, that'll teach her to shop LESS!!! . Modern cars and transponders seems to have cause more issue than solved.

Anyway hope this thread's part useful for those unfortunately soles encountering similar issues.

[PaulF]

Glad to hear that you're back up and running. As you say, hopefully you've saved some others from suffering similar pain in future.

[93_Clubman]

SOLVED!!

Good stuff!