During my recent changeover from seized Crane XR700 electronic ignition, back to condensor and points, I went through a few adjustments to get car to drive well again. I replaced coil, points, condensor, cap, then adjusted timing and car started right up. Went for a drive and car felt like it was bogging down above 2500 rpm. Measured what I thought was a good used ignition coil, but primary resistance was too high. Replaced with new Beru unit and car ran great. But then there was the tachometer. The needle was fluctuating, jumping, dropping. What had I missed? When I removed cap to inspect points, the cap came apart in 2 pieces! Hmmm, I recall this was just a Bosch cap in my "spares" bin, and perhaps it was the one from years ago that got swapped out as I was chasing a reason for misfire. I suspect now this cap may have had a hairline crack that I could not see, and finally it completed its goal of separating and it failed completely. Installation of genuine new Bosch distributor cap has completely solved the jumpy tach needle problem. Car runs exceptionally well. Happy to be back to points type ignition.
