mx5cartalk.com

So, my NB8B is not starting. Cranks fine, but seems to have no spark and injectors not firing.

I rigged up an LED / resistor to check for error codes, plugged it into the diagnostic port and turned the ignition key. LED lights up, but stays lit indefinitely. No blinking, just a solid LED.

I had a water leak into the passenger footwell a few weeks back.

So, my initial thought is water damaged ecu.

Any other suggestions as to why the solid LED / not starting ?

NB won't start guide: viewtopic.php?t=59479&start=15
NA no start guide: http://wiki.miata.net/tiki-index.php?pa ... tart+Guide
Sounds like it's the ECU, but the NB8B usual suspects to cause various issues are:
Spark plug leads/coil on plug setup;
Cam position sensor;
Crank position sensor;
EGI main relay;
Fuel tank electrical connector;
Fuel pump; &
ECU (if water gets into passenger side floor).
Might be worthwhile resetting/clearing ECU error/fault codes - just disconnect the battery & pump the brake pedal a few times. This full list will help if you're later able to pursue error/fault codes:
viewtopic.php?t=67370

Hey Dave,

If you want, shoot me a PM or email, happy to tee up for Lindsay and I to drop around after work one day with my OBDII scanner and see if theres any stored codes.

If it's a dead ECU though, I can't help with that.

Using an OBDII reader on it depends on what year NB8B it is as they didn't get an OBDII port until 2002.

Thanks for the kind offer, but its a 2001, no ODBII

Haven't had a chance to do anything with it yet, just got back from the track day today. I'll have a serious look on Anzac day. No rush, my brother is overseas for a few weeks so I've got his 350Z to drive

Spark plug leads/coil on plug setup; - tried a spare set , no difference
Cam position sensor; - this or crank was my first thought - it was getting a bit harder to start when hot for a few days before it gave up completely
Crank position sensor;
EGI main relay;
Fuel tank electrical connector; - getting fuel to the fuel rail, just not injecting
Fuel pump; - see above, and has had a new pump recently
ECU (if water gets into passenger side floor). - had an inch or two of water in the passenger footwell with all the rain a few weeks back

1600Dave wrote:ECU (if water gets into passenger side floor). - had an inch or two of water in the passenger footwell with all the rain a few weeks back

Start with the most obvious thing first, pull the ECU and have a look inside the case!

1600Dave wrote:Fuel tank electrical connector; - getting fuel to the fuel rail, just not injecting

Yeah, check ECU then, given above re fuel not injecting, check EGI main relay & fuel injection fuse.

Thanks for the suggestions, turns out it was a waterlogged ecu / water in the ecu connectors / water somewhere. Amazingly, after drying out for a few days, its running perfectly again You can see the "high tide" mark on the underfelt, plus see a bit of a a stain on the bottom of the ecu case.

Next step is to take the passenger seat, all carpet and underfelt out of the passenger side to let it dry out thoroughly, investigate why its leaking (it did get a new softtop fitted a few months back, perhaps not fitted properly ?? ). Plus take the ecu out and make sure all connectors / terminals / etc are clean and making proper contact.

That is a dirty flood.
I would dismantle the ECU and give inside a clean.

I was thinking the same. There's a place near me that fixes ecu's, might get them to check it out. I'm hopeless with electrickery.

Water seems to have leaked in from the softtop / rainrail area, run down behind the passenger seat, under the seat and collected in the front footwell. Its usually parked nose downhill, all the water has just run to the front.

1600Dave wrote:it did get a new softtop fitted a few months back, perhaps not fitted properly?

Reckon the rainrail may not have been refitted, or refitted poorly, or it was refitted in poor condition. Alternatively, the soft top drains either side of the cabin behind the seatbelt towers may be blocked.
Manga_Blue has mentioned a process for the inside of ECUs:

manga_blue wrote:I had a low load intermittent miss that just appeared in the last week or two. This morning I took out the ECU, removed the top and bottom covers, drenched it in electronic circuit board cleaner and then covered all the circuit board and connectors with a mist of INOX MX3. Miss is now gone.

manga_blue wrote:I moved it up into the glovebox a few years ago because it showed some case corrosion from being down on the floor. It never leaked down there but it can get musty. I'm very close to the beach, it's salty here and that doesn't help. If I'd been feeling braver I would have done the full job and dunked it in distilled water, then alcohol and then sprayed it with PCB cleaner, then Inox.

https://mx5cartalk.com/forum/viewtopic. ... start=2445

93_Clubman wrote:Alternatively, the soft top drains either side of the cabin behind the seatbelt towers may be blocked.

We have a winner. Not blocked by the usual accumulation of dirt and gumnuts, but by a "xmas tree" trim clip. A byproduct of having a new softtop fitted ?? Or perhaps just an errant clip from somewhere ??

Regardless, the clip had pretty much completely blocked the passenger side drain. Was a pain to get out as well. Hopefully that's the end of flooding, ecu comes out this weekend for investigation / cleaning of wiring connectors.

Crikey, the rust! Just saw your pics of ECU cover & footwell area around ECU - good that you've ID'd the cause.