Why are Mallory caps different colors? I am having an ignition problem with my 1987 Crusuader 350/270. I replaced the dist a few years back. Then I installed a Perko electronic ign sys in. The dist is a YL and came with a blue cap. Now I have a black cap and the engine won't run right. Almost like it is missing. Not backfiring like crossed wires, but not firing.