This can't be normal for my dist cap...

[chrisbruck]

Check out this pic... look at the center point that touches the rotor. Is this "normal"? Bosch cap and maybe 15k on it. I swear there used to be a pin or nub that looked like a BB. A tiny little gray nugget if you want to call it that fell out when I pulled the cap off. It was very small and not really round. Didn't think much about it and put the cap back on and the car seemed to run fine... I went ahead and swapped it out with my old cap that had a pin in it just to be safe until I get a new one. I can't imagine only the spring would make a reliable contact to touch the rotor.

Was this disaster about to happen? Did the center pin burn up? Very odd it still ran too.

[proporsche]

yes most likely it burned away or got destroyed to powder,it is after all graphite made.
Get new one ..or what is wrong with your old one?
Ivan

[76FJ55]

That is definitely not normal. As you say there should be a conductor (carbon) that the spring holds against the rotor. without the carbon there ends up being a gap between the spring and rotor conductor that the spark has to jump, similar to the gap between the outside end of the rotor and cap and the gap at the spark plugs. depending on the size of the gap sometimes the spark can find an easier path rto ground and you will loose spark at the plug, but in your case it still followed the designed path and the engine continued to run. In general it is harder on the coil as it needs to generate a higher voltage to get the spark to jump the additional gap distance in the system. the time to build the higher voltage can also delay spark timing, but this is marginal comparted to everything else.

[icarp]

The dist shaft bushings look worn out as well , the posts are also very worn

[GG Allin]

My car actually ran, at Road America no less with this one. Made the drive home too. I had no choice.

[eastbay]

End of life for sure, they will run like that until they don't

[porsche930dude]

Once my co-worker's honda civic stopped running and i figured out it was that same problem. His spring was burnt up completely so it wouldnt jump the gap anymore. I put a spring from a ball point pen in there and sent him on his way. I dont think he ever replaced it. Eventually he got a pickup truck a year or two later.

[nospiners]

ive gone through 2 of them in 35k miles. now i always keep a spare.

[chrisbruck]

I just checked my records... 16k miles on in, street car too. Shocked it happened so quick. Car runs great and no issues.

[Walt Fricke]

As you can see, the spark will jump quite a gap. I had this happen to me, though only the conductive tip and spring were missing. In your case somehow the tip of the plastic casting broke off. Icarp's supposition of worn bushings could be why.

[john walker's workshop]

Msd?

[smadsen]

There is a bakelite/plastic spacer on the distributor shaft. Over time they ALL rot, crumble and land in the bottom of the case. The then missing spacer allows the distributor shaft to then "slide hammer" up & down every time you throttle up/down. Over time that action can dislodge the shaft bearing. When the bearing finally falls out, the shaft can flail around and do some expensive damage to now unobtainable distributor parts. Remove the distributor ASAP and get it fixed with a suitable number of stainless shims and a new bearing. If you don't, the new cap/rotor will prolly end up in similar condition quickly. The fix is pretty cheap right now.

[Gordo2]

Icarp hit it - your distributor needs to be rebuilt / the distributor shaft bushings need replaced.

Wobbly shaft (due to worn bushings) allows the distributor rotor head to physically contact the cap, and make a large gap for spark to jump…

Look here: 83 SC Ignition Distributor Bushing Replacement

Not too expensive to fix if you can DIY.

Good luck,

[chrisbruck]

Interesting... and it's the stock coil for me, not MSD or anything fancy.

I'll be sure to pull it off and look closer at that distributor for any free play today.

[chrisbruck]

So I pulled the cap off again and checked the distributor shaft for play. Zero play side to side and just very very slight axial (in / out). I think it's fine for the time being and I'll just keep an eye on the wear patterns.

[PeteKz]

Are you sure it was a genuine Bosch, not a cheap knock-off? Maybe the contact in the center of the rotor was bent? It should have lasted many times 15Kmi.

[smadsen]

With the distributor installed in the car (and the gear engaged in distributor drive), the shaft may not move around much. With the distributor out of the car, give the shaft the wiggle/wobble test and the up/down test. Also visually check for the aforementioned spacer. It won't take much axial movement to beat the crap out of the cap in pretty short order.

Good luck.

[smadsen]

Another thought. I'm not sure what car you have, it looks like a big bumper SC in the background. It doesn't look exactly like an SC cap to me. Looks like it has a tab on the outside for a hold-down and possibly some kind of fitted plastic dust cover on the outside. Both of those items would not be on an SC cap, I think. The inside of the cap also looks a little different from my SC cap. You may have a proper rotor with the wrong cap causing your grief. Just some thoughts to look at.