MX-5 OC Forum

Ok I’m a newbie so bear with..

I have a MK 2 1.6 1998 model

It started having a mis-fire problem so I took it into a garage; they diagnosed it to be a coil pack problem and ordered one. When it arrived they couldn’t fit it as it was the wrong one and said they would track down the right one and let me know when they got it. In the meantime they asked me to take the car home.

It was now running rougher than before, so when I got home I looked under the bonnet and noticed they had reconnected the leads in the wrong order, once connected correctly I was back where I started. Not happy about the leads though.

I looked on flea bay to see if I could track down the right part, I saw one that was supposed to be for my model and year so bought it.
It arrived and looked on here about how to fit it so thought I’d do it myself and save some money.
The problem was it was not the same as the original.

The original one had a connector on each coil with 3 pins (red / black/green) and (red/black/blue). These two come together to one loom connector with 2 rows of three pins. A six pin connector.
The one I bought only had 3 pins to the loom connector (red/white/black with white)

I stupidly thought that they must be doubled up and spliced in the bought one on the original’s wiring connector.
Using one of the reds to the on the six pin connector to the red on the three pin and then the green to the white and the blue to the black with white, assuming these to be the triggers.

Obviously this didn’t work, the engine cranked over but no spark, so I thought ok I’ll put the original back. Unfortunately that now doesn’t work either, same problem the engine cranks but no spark on any of the leads.
I have checked every fuse inside the cabin and under the bonnet I can find – nothing blown.

What am I missing, what kind of damage may I have done?

I now have got a correct replacement coil pack but have not yet tried it in case I damage it before I know where the problem lies?
Any help gratefully accepted and appreciated.

Sounds silly but have you tried to disconnect/re-connect the battery and see if that helps? could the ECU have gone into a safe mode? Relay blown? 

Are you geting a spark when cranking over? 

Coil packs! some people think they are better than the good old coil!! But they are basically the same.

Did you try the replacement coil before changing wires around etc?

are the spark plugs OK? did you try grounding the plug to the coil (remove coil pack stick the plug in it and rest it so the plug is grounded to the engine then get someone to turn the ignition over briefly to see if there is a spark,) thats a start and you know the coil is working or not. I do not know a lot about coil packs so can only offer what I have done in the past, our last couple of cars had these and spark is everything to start the investigation. The HTleads also could be the problem if you are going to check the spark strength and one is has a weaker spark swop the leads around to see if the spark is better or not.

the best thing to do would have just to connect the replacement checking for spark, in my experience a lot of cars do not always have the same wires year on year, have a look at any Haynes manual!

it does sound as if you have fried the other coil by connecting those extra wires together, but if the replacement is exactly the same then you should be able to try it, but I understand your concern.

personally I would have turned the car around and taken it straight back and asked what the hell they had done as it was worse than when you took it in,but in anycase I wouldn't be going back there! 

Also any chance of a picture that always helps! HTH as said not an expert but used to digging about for a reason! (and dont like spending when I dont have to!)

Yes I have disconnected the battery, not sure about relay problem, which one should I be looking at?

No there is no spark from either coil, bear in mind this is the original one back on that was working ok but with occasional misfires.

Is there a fuse that may have blown that I'm missing?

A wiring diagram for mk2 1.6 1998 model may help me if any one knows where to find one?

I couldn't test the replacement without splicing it in to the original's wiring (the original one was not attached to it) because the connector pin was different (original was 6 pin the replacement was 3 pin).

The plugs leads et al should be fine as they were fine before?

Is power getting to the coils now, since your brief rewiring? It could well just be coincidence and all the fiddling has blown the coil pack for good.

If there's no power getting there, then yes it will be a fuse or the relay.

edit: it is also I guess possible that the CAS may have disliked having its outputs joined together...and shorted out. But I don't know enough about the wiring there to know if that's possible or not.

Good idea, I'll check to see if there's anything on the connector.

Each coil has 3 wires red,black and green or blue (assume these are the trigger wires).

Should there be a constant voltage on the red wire and ground on the black and a pulse on each of the green and blue ones to trigger the coil pack?

petercassidy:

I couldn't test the replacement without splicing it in to the original's wiring (the original one was not attached to it) because the connector pin was different (original was 6 pin the replacement was 3 pin).

The plugs leads et al should be fine as they were fine before?

You have a question mark after the leads sentence! so I guess you have a bit of a doubt, you can swap them around with the other coil to see how good the spark is. I think the main mistake was the "splicing" ! if it dont fit first time dont try to adapt, when it comes to car electrics! Just had a nose thru my Haynes manual and basically according to that, check the spark, check power is going INTO the coil and coming back out via the HT lead (earthing plug) if there isn't or it's weak swap them etc to check. Then it is the coil pack and or the HT leads. DONT mess with them cos they can give you a kick in the teeth voltage wise!  

But then again the garage should have done all of this in the first place!

There is no spark.

I don't think the leads are at fault as they worked before.

It is looking likely that there maybe nothing going in to the coil pack after I messed with wiring, as I said the original coil pack has not been tampered with and worked mostly ok before I started. So the splicing must have buggered up something else which means there's nothing getting to the coil pack now.

What hould I be seeing going into the coil pack voltage wise?

Just to make it clear I messed with the wiring trying to connect the coil pack with only a 3 pin connector. It did not work so I went back to original coil pack and original wiring which mostly worked beforehand. This is now not sparking on any lead. So logically I think I messed something else up which provides the electrical input to the coil pack.

Any ideas where to look, fuses ? Relays ?

Whilst I have the coil packs off, are there any checks that I do on them with a multimeter to see if they are ok before I connect to wiring loom?

Yes, you can check the primary and secondary windings for resistance:

Primary: <1ohm

Secondary: 11.2-15.2 kohm

I would imagine the igniter might actually be blown if it got shorted...

Not sure this model has an igniter, isn't it built in the coil pack? Model 98 1.6 mk2

Which pins should I be measuring across?

Ok just put a multi meter across the 3 pins coming out of the car loom to the coil pack.

Results are with ignition turned on

12v on the black/white wire that goes the red wire for one coil

12v on the brown wire that goes to the green wire for one coil

0v on the black wire that goes to the black wire for one coil

Same results on the other row of three pins that go to the second coil (obviously the green wire to the second coil is blue though)

These voltages are not present with the ignition key removed.