So leading on from my other post, which was about the rough running of my 76 Pre He I have worked through the injection and so far have not found any faults. Yet to check the fuel pressure which is fairly critical but awaiting a new Gauge for that. In the meanwhile I decided to put a spark plug tester onto the lead. The spark is pretty weak and pathetic. Its running the original Opus and even has the original coil Mind you I have never had a coil let me down in 50 years of playing with cars. Its showing 1.3 Ohm resistance. Amplifiers I have experience of letting me down when they get hot, but not being poor sparkers when cold. I would be interested in your views on the weak spark. Car runs poorly, starts fine just misfires.
Weak spark is definitely not good. IMHO, chances are better that the original Opus is the problem rather than the coil, although the coil is a definite possibility. I would recommend you don’t even bother with that thing and go ahead and retrofit the later Lucas CEI (including a distributor change) rather than fiddling with the Opus. Either that or go with an aftermarket ignition system. There’s even a kit for installing a Lucas CEI that looks like an Opus for those who care about original appearance. The message here is: the Opus isn’t worth the time and effort.
Ok, I shall consider a change but I have narrowed the problem down to two HT leads not getting any spark at all. Looking inside the cap there has been no arcing activity between rotor arm and two of the terminals which are virigin new. These correspond to the two cylinders not sparking. I am assuming its a faulty timing rotor ( the flat plastic disc that holds the 12 ferrite rods that stimulate the timing pulse) I have heard these can go bad so I have ordered a new one. Will see whether this returns my spark on the two cylinders in question.