Melted ignition rotor....Jeep left me stranded.

Ok, background to this weird issue. Ive been noticing some breaking up of the engine while driving. Kind of a weird hesitation that was intermittent. The only thing I could track down was the TPS. So I changed it for a new one. That fixed it for a bit.

Friday, on my way to finish my xmas shopping, it broke up real bad, ran ok for about 2 more seconds, then shut down on me. Crank, crank, crank...no start.

Things I was thinking at first were fuel pump, or CPS. I wasnt getting a code, so I figured fuel pump. I got a tow off of the highway were I was stranded...in the pouring rain. Got it home, and after some testing, found out I had no spark.

First thing I did was pull the dist. cap. The rotor was in a few melted pieces. It looks like it was on fire. All inside the cap you could see were melted plastic was slinging around.
The metal contacts that are normall in the rotor were just layin on top the distributor.

I just HAPPENED to have a new distributor, cap, and rotor in my garage, so I replaced it all. The dist. had a lot of melted plastic on it, and since I had the parts, I figured what the heck.

Ok...what the heck could have caused this? I had an MSD coil installed. Is it possible that it went crazy and supplied too much voltage?? The other idea I had was I did some extended highway driving awhile back. Where I was at like 3000rpms for alittle while. Could this have caused the rotor to get hot and meltdown?

Ive never seen this happen before. It was a new cap and rotor that I installed at my last tune up. Which was only about a month ago.

Any ideas?

Justin

Thats really odd, I have run into broken rotors before but never melted ones. I really don't think your MSD could have caused it though, never seen an MSD cuase that at least. Keep us updated. I would also go get another cap and rotor and put them in the jeep incase this happens again.

Yeah ive never heard of this happening. Right now I have the stock ignition coil hooked up. I secured it next to the MSD one so I can switch back and forth if I want. I just didnt watn to burn up the new stuff right away.

And good call with the spare parts. I actually already had a spare cap and rotor in the Jeep. And I wish I knew what it was when I was standing on the side of the road. haha. But it was raining its butt off, and I was parked between and offramp and a busy highway. Just couldnt diagnose anything at the time. I wish I would have known it was just the cap and rotor, because I could have swapped it there and saved myself the $80 tow bill.

Ill post a pic of it in alittle while... Its kinda funny looking.

Justin

Maybe a distributor shaft seal allowing oil into the cap? Any oil that leaked would burn in the normal shower of sparks in there.

There were no traces of oil anywhere. Dry as a bone. When I changed out the distributor, there was no obvious play or issues.

OH...and just for kicks. While the cap and rotor were off, before I removed the distributor, I put a dial indicator on the distributor shaft and cranked it. No play at all. I know that thats not the same as high rpms...but still. It was something that I thought of.

Justin

Re: Melted ignition rotor....Jeep left me stranded. PICS ADDED!

Here are some pics. The white powdery substance seems to be plastic, not corrosion. But I guess it could be corrosion...not sure. Dont forget, this cap and rotor is probably less than a month old. It seems as tho the rotor was hitting somewhere and being shaved away. Also noticed the swirl marks around the inside of the cap. Like it was slowly falling down while spinning. Just kinda funny looking. haha. Also the electrodes inside the cap have grooves from the front of the rotor hitting them. Kinda hard to see...but here are pics since this obviously doesnt hapen every day.



















Justin

Just cheap as after market parts, where did you get them?

Looks as if the rotor was a hair too large OR the cap was a hair short in diameter OR the cap was not exactly centered when replaced.
Looking at those photo's brings back memeries of an old 39 ford coupe convertible that my aunt drove. Yes, it had one of those pop up rumba or rumble seat in the trunk area.
Well, the old ford developed a fuel line leak right above the distributer on her way home from work.
The dist cap exploded into 2 halfs and cracked the rotor in half.
I would not have believed this if I hadn't seen it. She had a roll of scotch tape in the glove box.
She taped the cap and the rotor back together and drove over 20 miles to home.
Believe it, I saw it when she got home.

Autozone... But before anyone says anything about Autozone... I always use those duralast parts. I had the other cap and rotor on there for a year with no issues. Still looked new inside. I changed it merely because I was doing a tune up. My parents ZJ, any cars I work on... they always get Duralast parts. Unless I want to spend more on the Duralast gold... But Ive never had a problem like this. No one else has that I know of either. Maybe alittle bit of build up. But my accel cap had that on my Firebird as well.

But seriously. Even if the parts are junk, I still dont see how the thing melted down and destroyed itself.

Actually...I did come up with a possibility. I wonder if when I was tightening down the cap the last time, if I didnt get it seated all the way. Like maybe I was afraid to strip the bosses on the distributor, so I kind of snugged them then stopped. If there wasnt proper contact between the rotor and the cap, there could have been arcing. That would cause heat right?

One other question. Does the output of the coil increase with RPM and engine load? In other words...is there a difference in coil output between cruising down a back road at 40mph / 1500 rpm vs. 70mph / 3000 rpm???

Just curious. I thought they always output the same amount of voltage no matter what.

J.

P.S. parkeruph...haha thats pretty crazy. Ive held some stuff together with duct tape and rope to make it home. But never a rotor with scotch tape. haha. I think you might be right with the parts being out of spec. I guess thats what langer1 was referring to when he said cheap parts. That I can see...

BlueCuda said:

Thats really odd, I have run into broken rotors before but never melted ones. I really don't think your MSD could have caused it though, never seen an MSD cuase that at least. Keep us updated. I would also go get another cap and rotor and put them in the jeep incase this happens again.

Click to expand...

Did you install a ballast resistor with your MSD? If not, it will get too much voltage and eventually something will catch fire. My brother in law almost lost a custom '69 Camaro to an MSD.

Jeep MSD don't need a ballast resister, the 69 Camaro was a whole different system.

I use the AutoZone cap and rotor without a problem. Not to say something can't even be wrong from them, though......

The rotor shouldn't hit the distributor cap at all. There should be arcing. Looks like they were touching and that's bad.....

Take a stethescope to the new distributor cap and you shouldn't hear any scraping or anything.

I just wonder if the bearings or bushings got so hot in the Dizzy it melted the rotor?

Yeah there is no resistor with the MSD replacement for the Jeep. It looks like the stocker except its red. I only had it on there because it was free. I have no supporting mods except for a high flow cat and flowmaster muffler. So I didnt expect anything from it.

As for the arcing...I meant between the center electrode in the cap, to the top of the rotor. Those touch do they not??? The car goes from the tip of the rotor to the outer electrodes for the plug wires. And I dont think the rotor was touching those until it started to melt and go crazy.

langer1: When I pulled the cap, the part of the rotor that sits on the dizzy shaft was still there. Thats what so weird. That part of the rotor was still in good shape. It will slide right onto a dizzy shaft and index itself and all. Its just like the top part, and front part of the rotor got hot, and flew apart while spinning.

Im really stumped on it. Im not going to re-install the MSD just in case. I need the jeep to make an hour trip this weekend...then get me back home. So Friday, after driving the Jeep back and forth to work all week, Im going to pull the cap and see what things look like. Keeping my fingers crossed that it looks good. I also plan to stop about halfway on my trip, and just check it again because Ill have to do some 65mph cruising. Just so it doesnt happen at an unoppurtune time.

The Jeep is running great now by the way. No noises, no breaking up, starts up fine... So hopefully I can chalk it up to a crappy cap or rotor. I will however grab my stethescope and give it a listen just for the heck of it.

Thanks for the input guys!!!

Justin

ghettocruiser said:

Autozone... But before anyone says anything about Autozone...

Click to expand...

They built an AutoZone near me about a year ago. I've gone in there a total of 6 times. Not once did they actually have the part I needed in stock. This is common stuff like a Jeep 4.0 distributor cap and radiator hose. I even got into an argument with the counter flunky who kept insisting that my Jeep didn't have a serpentine belt as I'm standing there holding the old one. Last time I stopped in, they didn't have standard wattage H4 bulbs on the shelf but the idiot kept insisting the I should buy the $40 set of 9004 SilverStars because they used the same plug and were twice as bright (they were stock wattage). No wonder the parking lot is always empty.

Oh I see what you're saying. Yes, the top of the rotor should touch the center pin of the cap.