Help needed, no spark

Jaguartvr · #1 17th August 2014, 19:10

Picked up a salvage 2003 mx5 as a doner.
Car was running when it was in the salvage yard, picture of the dash with the rev counter working and no engine light on on the dash.

Car delivered to me but flat battery, jumped but will not start, no spark.
Insert key and the key symbol in the dash goes out after 2 seconds, should mean immobiliser is turned off, but not convinced.

Can't get a fault code, RAC no help said his box could not connect or see the ECU. Bought a cheap reader from ebay, comes up with no error codes but will not reset engine management light. Problem seeing ECU?

My thoughts, could the problem have been caused by the jump start?

Faulty immobiliser, which I believe means replacing ECU, ignition lock and immobiliser box

or

faulty crankshaft position sensor

or

faulty camshaft position sensor

Anyone have any thoughts? :no idea: Doing my head in.

ukhozi · #2 18th August 2014, 10:16

Unless done correctly jump starting can create a whole bunch of problems and the ECU is usually the first to suffer. If a OCBII reader can't 'read' the ECU I think you have the answer.

Jaguartvr · #3 18th August 2014, 11:32

thanks, that was my thinking but wanted to make sure first.
Jump started hundreds of cars over the years and ha a problem so far.

ukhozi · #4 18th August 2014, 11:50

I would be inclined to 'borrow' a ECU and try that first, but if you cant read it, hmmmm..I'm pretty sure that's it, always a first time

Jaguartvr · #5 18th August 2014, 12:18

Trouble is you then need to borrow the matching immobiliser and immobiliser ring from the ignition and the key.
They are all apparently am matched set. Then it needs to have the same code number on the ECU as the one on the original car. If you look on ebay there are loads of matched sets but then you need to change the door lock, ignition lock, glovebox lock......the list goes on. Personally I would prefer a crook lock!

Saying that, does anyone know of an MX5 thats been stolen?

Spoke to a very knowledgeable and helpful chap at Maztek in Slough and it seems that the ECU is quite suseceptable to damage on these cars. He said it is better to get it repaired then replaced so you don't have to change all the locks.
I'm going to send it to the ECU doctor, they fixed the ECU on my TVR in a couple of days when all the garages could do was scratched thier heads. Will let you know how I get on.

On point that Alan from Maztek made was that the MX5 must be fitted with a gel battery as the vent into the passenger compartment. Something I had never thought about and may be relevant for some of he builders on this site.

fatbloke · #6 18th August 2014, 12:29

FYI, I jumped the cam belt on my MX (don't ask) putting the crankshaft sensor out of postion. It wouldn't run but there was still spark, ended up at my local independent garage to have the timing reset and a new cam belt.

Could it be a problem with the coil pack?

Jaguartvr · #7 18th August 2014, 12:43

I am going to "borrow" a coil pack from my daughters mx5 (my original doner!) when she comes home on Wednesday. I do think it unlikely that both will have gone together but they do seem to be another weak link.

ukhozi · #8 19th August 2014, 07:35

The 'reader' on the ignition lock is just a dumb reader, any key, tape the replacement key to the steering next to the lock and swap the ECU and use the key with the battery remove to crank it over key, it should work, even if the key has a 'passive' transponder chip it should only read the 'correct' key for the ECU.