No spark when engine is hot

[Biffdiff42]

Hi I have a Rover 3.5 V8 sd1 motor circa 1980 in a TR7 and have a problem with the engine cutting out when it is hot. The engine starts very well when cold and gets warm nicely but when hot the engine cuts out as there then no spark, and will not go again until it cools down. There is plenty of fuel as the car back fires as it starts to cut out.

The ignition set up is Lucas 35DLM8 2585 which is the early type of electronic ignition and it has an Amplifier on the side of it. It has new coil which I had relocated away from the rad and water pipes to try and keep it cool and and it is the non ballasted type so the ballast resistor sits behind it. The coil gets warm/hot but I can keep my hand on it. The plug leads and spark plugs are new.

I have fitted an electric fan to keep the whole plot cooler and this seems to work very well.

Where should I look to find the problem and what practical steps can I take to identify the root cause. I have only basic electrical knowledge so any advice or guidance is very welcome as I am struggling to know where to go next !

I have attached a couple of pics to show the set up.

thanks

Jonathan

[Biffdiff42]

I have also now removed the current coil and checked its primary and secondary circuit using a multi meter and obtained good readings from it, but it was cold. I then put it back on the car and tried to replicate the problem by running the car stationary but could not get the fault to re occur. I could drive it down the road again but risk of a random stop at a bad spot is not a good thought.

[GDCobra]

I had a similar problem with an SD1 era ignition amplifier (the type that was like a box with the coil mounted to it) several years ago, eventually the symptoms 'improved' in that the device failed completely so allowing me to narrow down the culprit.
I replaced this with an aftermarket amplifier but I believe it is now possible to buy just the guts of the standard amplifier which should be cheaper.
There is a thread on here somewhere about the modification.

In fact it's stikied right at the top of this section.

viewtopic.php?t=78

[Biffdiff42]

Thanks, I have ordered the replacement ignition amplifier and will let you know how I get on once it is installed