Spent all This Sunday trying to sort problem of no spark to plugs. Isolated imobliser all ok. Think it could be Camshaft or Crankshaft sensor should I do both or try easy one first. Car was running perfectly one day then nothing turns over ok. Can anyone point me in the right direction please. I amnew to club so hope this. Is the correct way to ask the question.
You do know that if you try to turn the car over without the plugs being connected to the leads and the bodies of the plugs earthed, that you can damage the coil packs.
Assuming a Mk2 so between 1998 and 2000 you could have a number of problems.
The ECU has gone faulty, probably not.
The camshaft sensor only switches either pack on the coil pack on or off so I think it may run rough rather than not run with that not working but I could be wrong.
The crankshaft sensor would seem a reasonable start.
I assume if it is the coil packs only one side would go at a time and would work when it had cooled down.
A bad earth from the wiring is a possible.
Finally if the cam for some reason has jumped a number of teeth, then the ECU will get confused as the cam and crank sensor will send a their signals out of phase. So lack of spark
I assume you have an LED and know how to use it to get error codes from the ECU. Not that you always get an error code as I can testify.
PM me your phone number as I have been all through this, if you want to talk prior to throwing something heavy through the windscreen!!!
Cam or Crank sensor can cause non start.Check ecu area ( under passengers feet ) for signs of dampness It is possible that may be the problem but we have ecu set s for sale.If it was me replace cam then crank take it from there.Very unlikely tming belt has broken really but it can happen.Most non starts on mx are immobiliser but you say you disconnected it .From where or is it aftermarket ??
Thanks for your reply by strange coincidence the evening before the car gave up we had the most horrendous storm. The carpet is wet but guess what it’s raining again. Will keep you informed. Regards from Alan.
To go from working fine one day to no spark at all on any plug is a bit odd, but happens sometimes on any engine.
I’d start with the engine earth - if it isn’t earthed, no matter what else you can’t get a spark. Check the earths and if required rule this out using a jump lead from the engine to a good earth, even better all the way back to the battery earth to avoid any other issue. Also check the battery positive and negative connectors.
It doesn’t sound like the crankshaft sensor to me. Ours had this fault recently and it ran fairly rough but turned over and had a spark - even if the spark wasn’t exactly at the right time.
I’d also check connectors to the coil pack and make sure ECU is bone dry as suggested already.
Where are you based? There may be members locally with spares you could try out. We’ve got a crankshaft sensor which is goosed but does provide a spark that you are welcome to try, but the postage cost is probably more than a semi-functional sensor is worth!
Jack.
I am based in Stevenage Herts 1st job is to try and dry out the ECU then sort out why it’s getting wet. Once again thanks will keep you informed. Alan
We are in WD4. If you have Kit Kats and cans of coke I am happy to come over one night later this week with the old CAS and have a play if you want, Thursday probably best day my end. Sometimes two heads and all that. PM me if you are around and want a hand, I am by no means an MX5 expert but do understand the basics and have a few spare bits you can play with to try and rule things out.
Jack.
Help needed - I don’t have a wiring diagram for a MK2.
We went through a few things tonight, and there is no issue with engine earth straps or anything, car is turning over healthy enough but literally no spark at all even earthed back to the battery.
So investigation turned to ECU where Alan has found a lot of water. ECU out and there is corrosion on the 4th pin from the end, which has a red on green wire leading to it - this wire has broken and there is corrosion on the pins in the ECU and no connectivity where there should be.
We can deal with reconnecting the wire anyway, and ECU looks like it will need replacing, but can someone have a look at what the red on green and red on blue wires are going in to the ECU to check if this is likely to be causing the fault?
No reason to particularly suspect the sensors yet, there is power to the coil pack but no spark.
Final question, can you just replace the ECU with another one with same codes on it? Doesn’t it need to be swapped with the right key/ignition?
Jack.
Unfortunately on the Mk2 you will need to swap the ECU and immobilizer as they are paired and that also means getting hold of a key with the relevant immobilizer code. Places like Autolink will do a kit with all the parts you need, you then just need to find a key place that will cut you a new key to fit the existing locks but with the chip coded for the new immobilizer.
So we can get the new ECU, ignition barrel and key from another car and swap them over? Of course that means door locks will be different to the ignition but it would get the car moving and confirm suspicions on the ECU fault causing the spark issue.
Does anyone know what the red on green wire into the ECU does? I’ve checked Haynes (ha ha) manual and it looks like Red on Green from ECU is “VSS Input” - what is that?
Finally is there a good company that can effect what will be a minor repair to the ECU board, and if we did that assume that would avoid swapping keys and ignition etc over? Probably half an hour of work for a very skilled electronics specialist, perhaps worth a go before we get elbows deep on this one?
Jack.
First of all a big thankyou to everybody who has helped with my sick MK5 MK2 1998/99 1840 import. Still not fixed but have my fingers crossed this is by way of an update to those intrested some of it might help in the future.
- Not all imports are fitted with Immobilizers the owners manual ref 8n82 for mine showes 2 options you can tell if the ingnition switch has 1, 11, 111, marks adjacent to the 3 postions the car was not supplied with built in immobilizer.
- So I have ordered a matching ECU. Also sorting out the water problem with the drain tubes.
- I may still have problems with Sensor's but will change the ECU first.
Regards Alan.
Hi Alan,
Not sure it is the immobiliser that means the ECU has to be paired, but I could be wrong. Hopefully the new ECU works with what you have.
I am fairly sure, having felt the wet on that carpet and found the dead pin on the ECU, that if it isn’t what causing it, you soon would have had other problems, so this is worth doing either way. But I think we found something obviously wrong and that probably explains a lot of the problem.
Did you get the green/red and blue/red wires stripped back and new connectors onto the ECU plugs?
Let me know when you get the ECU through and I can come over - with the new ECU it can only be a couple of other things, my money after that would be an issue in the coil pack but not convinced on that yet.
Does nobody know what the VSS input is on the wiring diagram? Still not identified if this could be something that is killing the spark.
Jack.
Hi Jack still waiting for ECU but the VSS is the variable speed sensor. So looks like it could have got disconnected when I pulled out the connection into the ECU.
Regards
Alan
no it doesn’t the import doesn’t have the immobilizer in the ecu
just get an imort ecu from autolink
All sorted ECU changed started 1st time. Thanks to everyone at Owners Club who posted answers to my problem.
Alan this is great news. I got your PM, sorry for the slow response - I have been running around all over the place this weekend, amusingly getting a 50s car started this afternoon after 5 years laid up but glad to hear you got it sorted.
And great that we got it right on the ECU, I was worried the parts bill could have been significant if we had to get a new coil pack and/or sensors before we found the fault. Those dead pins were certainly likely to cause a problem soon enough if they weren’t the cause - always nice to be able to eliminate an issue.
Most importantly though will be to deal with the source of the problem. You need to sort the seal so that the water doesn’t pool in the footwell, no idea what the solution would be, suspect that is a new thread entirely! I have a dehumifier you are welcome to borrow and get everything bone dry again if you like.
Jack.