MatraSport Forum

After breaking down in October I parked the Murena up pisse* off and left it sitting forlornly on the front apron of the house. However as the spring approached I took it to a very local garage had had it for a few days and hey we are back on the road again the problem of the car cutting out was the coil he showed me the old one and it was in a state. They also freed off my brakes and fitted a new rear caliper which I had had since before Christmas. So I can return the used unit back to Will Falconer to get refurbed.
I was a bit peeed off with car and was intending to sell it but we are back on the road again and I think I will keep it. As it is such fun to drive Long Live MURENA ownership.
Richard

So... another broken ignition coil.... the plot thickens... :)

Congrats on getting your car running again! :)

You should have seen the state of the coil, it was or seemed very old
Richard

Was it orange?  I bet it was the original coil still!  This is what I mean when I say people don't maintain their cars correctly.  No Murena should still be running around on it's original coil but I know of another that is - it's a breakdown just waiting to happen.  Planned maintenance means replacing things before they are likely to fail, and expecting an original coil to still be fine after over 25 years is asking for trouble.

Roy

oh to be perfect sigh

Hmm, I do believe mine is still orginal Roy.... And it does still not run fault-free, perhaps it could be the coil...? Is there any way to measure if is is faulty...?

I would get a new coil right away.. razor.. at that age it might give up anytime.

The tests really are to take primary and secondary winding resistances and then check voltages produced.  Connect your meter between the two lucar connections (positive and negative) for the 12v windings - you should disconnect any wires first.  Then check between the H.T. tower connection and negative.  Primary should be about 1.5 ohms and the secondary around 8 to 10 thousand ohms.  Running the engine, H.T. output should be something like 25kV for a points/condenser set up, and possibly 40 kV for an electronic one.  Care obviously needed when checking H.T. voltages as well as the right equipment.

However, one problem is that resistance varies with temperature, so a common coil failure is when they get very hot after some period of running.  Also the coil is kept from overheating by the oil inside the sealed case.  But the coil body is aluminium and the clamp is steel.  Differential metal corrosion often means the oil starts to leak out by the clamp when the body becomes porous.  It can be so slight that you do not see it.  But when the top part of the coil has no oil it gets overheated and failure is inevitable.

The Murena 2.2 coil set up has a further problem.  The coil and amplifier are mounted on an aluminium plate which is in turn mounted to the galvanised chassis, and the amplifier relies on the grounding and plate contact for heat dissipation.  It is also a little difficult to get at where it is tucked away.  After many years if it has never been out you need to remove the plate from the car, thoroughly soak the screws with penetrating fluid, and remove the amplifier and coil.  Remove the inevitable corrosion behind the amplifier and put some silicon grease on the base to aid heat dissipation and then remount it to the plate.  Renew the coil, 12v coils are so cheap it is simpler to replace it but remember you need an electronic ignition coil not a standard one, clean the chassis mountings and replace the amp/coil assembly.

I also take the time to modify the mounting slightly which makes it easier to fit and remove in future.  You will probably have had to get a second person to help remove the original if it has never been off before.  Why?  The nuts are under the wheel arch and the bolt heads are in the engine compartment and they will spin around once loose!  I use longer bolts and two extra nuts.  Bolt everything up OFF the car, then fit to the chassis and bolt up using the two extra nuts.  It is now a one person job.

Roy

Roy, is there another coil than the one Simon has that can be used?

Couldn't you use most coils designed for a distributor system??

No, as Roy says: Pick a quality brand coil designed for electronic ignition. Not "ballast", and not one for mechanical ignition.

/Anders

Like....?

Bosch, MSD, whatever you can find with a recognised label on. Or order it from Simon, he knows the car and has good parts.

Yes, at least here in the UK it is fairly easy to obtain a standard electronic 12v coil.  The last one I bought for a job about a year ago was a Unipart one I think from a good automotive factor.  Cost less than £24 if I remember.  Can you not get anything?  What is Simon charging?

Roy