Re: 356 running rough and eating ignition points

Posted by HH56 On 2014/3/16 21:18:37

I'm curious on your first post you said there was ground on both sides of the points but no spark between. There should only be real ground on one side. The other side should be voltage if the ign is on and points are open. When the points close, the voltage should drop to 0 or ground. If you checked with an ohm meter with ign off then you are probably reading thru the coil but it is not an actual ground. Is that what you are seeing?

Since the issue seems to go away with new points any chance there is something with the distributor - either wear or something letting the settings or point gap change. Does the problem happen with car still and engine just idling or does it always depend on being in motion. I am wondering if something could be vibrating and shorting or has a loose and intermittent contact.

Be aware also, If you have an old original style coil, those are notorious for some strange and intermittent failures. Usually the symptom reported is once they get hot they just quit. An hour later when things cool, all is well again. Conceivably yours could be acting up to the point of rough running but the coil hasn't reached the absolutely quit working stage. Doesn't seem likely it would depend on new points to work properly though something to consider.

One other lesser possibility is the ignition switch or the armored cable between the switch and coil. The coil has it's own terminal in the switch and that could be heating up causing voltage to diminish or drop out. The wire inside the armored cable has been known to short against the armor.

If you wanted to totally rule out coil and ign switch, Since original style coils are so expensive, a quick, dirty and relatively inexpensive way to rule out coil is get a universal 6v coil from Napa for less than $20. Use some tie wraps around something handy to rig some kind of support for the coil in the engine compt. The case does need to be against a metal ground though. Reroute both distributor wires to the new coil and for power use a jumper to hot wire the coil directly and see if the problem goes away. If it does, the coil is suspect. If still a problem, go a bit farther by removing the power wire from the original coil end and extend it to the engine compt to power the test coil. Easiest way would be to remove the old coil and extend the wire thru that hole.

If you still have a problem then at least you have ruled out two places known for issues.