[Real McCoy]

I picked up a slight skip in my engine. So I'm doing some PM stuff tonight and while checking the Ohms on the plug wires I find the lugs inside the cap are dark colored and I have to scrap the lug with the meter lead to get any reading at all. The cap only has 130 passes on it. I pulled the rotor off and it too was dark and I had to scratch the tip to get a reading to the button pick up. I put the cap and rotor in the glass bead cabinet and cleaned the lugs up. Now they read fine. Anyone see this before? I run a crank trigger and this is a MSD cap, rotor, and distributor and they were all new 130 passes ago. Wonder if that could insulate the gap and hurt the fire to the wires? Maybe I'm just over thinking this? RM

 

[WJ Birmingham]

Sounds like the crank trigger wasn't phased to the cap correctly... But that's just a guess.

 

[Real McCoy]

I had checked it about 2 months ago or 30 passes ago and it was good then. I think the cap may not be vented enough. I thought about leaving the test cap with the 1 inch hole on the car. I just don't know so I asked. Thnaks RM

 

[69427]

Had a similar problem with moisture. MSD tech had me vent the cap more.

 

[Horndog]

Yep, needs more vent.

 

[CarbGuy]

I've had this happen on a number of marine engines in the past, we'd have to clean the cap and rotor monthly. If your racecar sits in a hot trailer or garage in the humidity it can happen.

 

[Real McCoy]

It stays in the shop mostly but I haven't been keeping the A/C on 100% of the time so it can get hot. It is SC you know......LOL. I drilled a 1/2 inch hole in the MSD cap to check the rotor phase and I'll leave it as a added vent. Do you think that coating can reduce the fire to the plugs? It can't help but does it hurt? RM

 

[Horndog]

It may add a little resistence but I wouldn't worry about it unless the engine develops a miss.

 

[CarbGuy]

Hurt? Maybe, maybe not at least to the point it's at right now, but why risk it?

 

[Real McCoy]

Well I origionally started all this checking because the engine recently picked up a slight skip. Very slight but you can heard it and it just happens once or twice a pass. I checked rotor phase, timing, plug wires, replaced the plugs and closed the gap to .035, checked float levels, valve lash, valve springs, and compression. Everything is spot on the same as it was in the spring. I'll go run it again Friday night and hopefully it will be fine now. If it don't skip the question would be was it the corrosion or the new plugs? The old plugs only had 30 passes on them and they looked fine. RM

 

[quickwrench]

The corrosion on the cap terminals and rotor could absolutely be the problem. I used to put just a skim coat of dielectric grease on the terminals and rotor tip on the big alky stuff, and checked to make sure the gap between the rotor tip and terminal wasn't too wide. It helped out a good bit with the carbon buildup. The hotter the spark, the more the arc is going to try to oxidize the air in the cap and coat the terminals.

I don't know if that helps or not, just what I saw and dealt with all the time. I coat all the cap terminals and rotor tips on customer vehicles now when we do tune-ups.

 

[Real McCoy]

Thanks, if the extra vents don't help I'll use the silicone. RM

 

[bottlefed1]

This might sound stupid... but also make sure you have a ground wire run to the block and heads. You would be amazed how many people still don't supply a reliable current path on the ground side and think chrome moly, iron and alloyed aluminum are a good electric cable

 

[Real McCoy]

Well, while I did run a separate wires from the battery to the chassis ground lugs I didn't run one to the motor. I'll do that today. Thanks, RM

 

[Real McCoy]

Well I got to make one pass before we got rained out but the motor ran fine, no skips and it went a 5.43 in 100 degrees on a track that was 145 degrees so I think it's fixed. Thanks for all the help and suggestions. RM

 

[AutoRoc]

My pickup/reluctor wheel was rusting really bad and FAST after being cleaned up. It would cause all kinds of mis-fires. My friends does not do this. The difference? My grommet was missing on the bottom of the dist. Where the wires go from the pickup through the bottom of the dist. heat and humidity from a hot engine, etc...No wonder it rusts! Silicone it up if you're missing yours.

 

[Real McCoy]

The motor was brand new last spring and everything on it was new too including the distributor so nothing is worn or missing. This is an empty flat cap no guts MSD distributor since I run a crank trigger. I'll watch it and see what happens. Thanks, RM