Carbon in cap/roter

On my 74, with the pcm 351, I too had black crabon in my cap, i found that it led to the plug wires arking inside the cap. I would change your plug wires to see if that fixes it.

79Tique wrote: Yeh, I'm going to replace the plug wires today. I hope that's the issue, but if there is something els I should check please let me know while I'm in there.

good luck with that let me know when it doesn't work.

Also get a new cap and rotor made by a quality manufacturer like "Standard Electric"

replacing the wires won't hurt any as it sound like they are quite old to start with but this will have no effect on the carbon tracks. You have excess moisture in the cap, a cheap cap/cracked cap or a really weak spark.


are you saying that the carbon is about the center area where the carbon button in the cap makes contact with the center of the rotor? or are you talking about the tower contacts where the tip of the rotor meets the individual contacts for each spark plug wire?

also are you getting the rotor seated completely? the only source is the carbon ball or arcing at the terminals, so if it is in the center and the rotor isn't seated all of the way it will apply excess pressure to the button and make it ware quicker than normal.

Some one suggested timing. Anyone know if that could cause this?

79nautique wrote: 79Tique wrote: Yeh, I'm going to replace the plug wires today. I hope that's the issue, but if there is something els I should check please let me know while I'm in there. good luck with that let me know when it doesn't work. Also get a new cap and rotor made by a quality manufacturer like "Standard Electric" replacing the wires won't hurt any as it sound like they are quite old to start with but this will have no effect on the carbon tracks. You have excess moisture in the cap, a cheap cap/cracked cap or a really weak spark. are you saying that the carbon is about the center area where the carbon button in the cap makes contact with the center of the rotor? or are you talking about the tower contacts where the tip of the rotor meets the individual contacts for each spark plug wire? also are you getting the rotor seated completely? the only source is the carbon ball or arcing at the terminals, so if it is in the center and the rotor isn't seated all of the way it will apply excess pressure to the button and make it ware quicker than normal.

Where do we buy "standard electric" parts???

NAPA used to carry them just have to ask for it. But use a quality part not the cheapist thing you can find atleast for the cap and rotor, wires no big deal you just replace them sooner. But spend the extra couple of bucks and get the good stuff.

79Tique wrote: 79nautique wrote: 79Tique wrote: Some one suggested timing. Anyone know if that could cause this? Also What plugs are you using they will effect resistance more than anything in the system. I was running NGK's but just replaced them with Auto lite's. Also I replaced the old 7mm PCM plug wires with a new set of Taylor 8mm and noticed a big performance increase. I think maybe the wire from the coil to the cap was the main issue. I guess I won't know for about 50 more running if the carbon problem is gone. With the change in engine tone and power increase I bet it's fixed.

if you just cleaned the contacts in the cap and the carbon tracks and didn't replace the cap and rotor when you changed the plugs and wires then you WILL HAVE THE EXACT SAME PROBLEM within hours not after 50, so replace them and you won't have to worry about them for maybe 150 hours provided the timing is set correctly.

once the tracks are in the cap they are always in the cap and you will never ever be able to clean it well enough to prevent them from coming back because it's burned into the plastic of the cap and returns quite quickly.

use autolite you don't have a foreign motor you have an american motor that requires america speced plugs.

just be sure and replace the plugs each year or they will rust in place, they do make a platinum series that are made with stainless steel and a marine series too I belive that are SS as well and those you do not have to worry about, so say use never seze on the std plugs but I never did just replaced them a lot.

I would always leave the old ones in for the first tank of gas before replacing them in the spring no need to feed new plugs junk, let the old plugs take it then install the new ones after the bad gas and fogging oil is burned off.

Should i use the engine fog? I just remove my water pump, drain the engine block and manifolds, then refill with antifreeze. Also i drain the float bowls to keep the floats from getting stuck open.

wow.

One can use NGK or autolites, or any brand as long as you keep all 8 the same brand.

Then again on my jeep forum I hear folks say you can ONLY use champion copper plugs because that is what they come with from the factory. LOL. 90k later on my Bosch Platinums and I still laugh.

German plugs on a 100% american 4.0 I6?
Or how about Champion (american) plugs in a japanese fuji snowmobile motor.

anyway....

74, you remove your water pump? do you mean the RWP, or the engine circulating WP? I do neither, but I replace the RWP impeller when needed.