Ignition problem pics attached

[Scott R]

I started hearing a popping in my exhaust, then I found that my CO levels can't be adjusted below 3% no matter how lean you have things set. This to me all points to a dead cylinder, but in testing today it seems like I have random dead cylinders.

Attached is a pic of my distributor cap it's scratched to heck inside! That's all the white marks in the picture. What would cause this? I don't measure any play in the distributor (it was rebuilt recently) so I'm at a loss.

What do you guys think?

[snbush67]

Is it possible that something is floating around inside? I would remove the distributor, shake it upside down and see if anything falls out.

[Scott R]

Ok, I'll go and pull it, good point.

[dfk911sc]

It looks like someone used some emory cloth to dress the carbon deposits. When it was rebuilt was the cap replaced? I ask because if something was floating around inside there would be mechanical damage to the contacts. Just my $0.02 worth.

[Targa Me]

Yup, it looks like something is loose inside that distr. Maybe a weight spring has broke and a piece is flying around.

[wwest]

Ignition is firing with the rotor not being close enough to a spark plug "contact" point.

[Scott R]

Distributor is on my bench, I can't find any sort of foreign material anywhere. The rotor itself is also clean, not scratched and looks as if new.

@wwest, have you seen this before? Because I'm leaning towards this as a possible issue now. I have a spare cap and rotor in a box and I'll replace it today however I would like to know the root cause.

BTW. This is a MSD setup with blaster high vibration coil and magencore wires. All of which is very new.

[Scott R]

I found a nasty arching between the end of the coil and the negative post on the coil. I removed the coil to find a complete hole in the side of the coil. Have a new one on order for next weekend.

[James Brown]

Yeah that will do it. Rember, in CDI systems, there is +300 volts going to the coil. YIKES! And get a new cap!!

[Steve@Rennsport]

Originally Posted by Scott R

I found a nasty arching between the end of the coil and the negative post on the coil. I removed the coil to find a complete hole in the side of the coil. Have a new one on order for next weekend.

Thats not an uncommon problem when the coil wire doesn't get seated all the way in the coil tower.

With MSD ignition systems, everything must really be perfect.

[DUK]

Also my .02. Make sure and use no grease on the rotor button. MSD's will make a mess with it and kill the cap.

[cudabnu]

Does the rotor itself have the built in resistor? the MSD's do not like this. If the top of the rotor has a section of black stuff between the the brass tip and the contact point to the top of the cap, then you need to get a different rotor. There should be a few posts with pics on this if you do a search of "MSD rotor" to discuss why.

also, what spart plug wires are you using with the MSD?

[Scott R]

The rotor does have the original resistor setup in it, I'll read up and find the correct replacement. The wires are Magnecore from our host.

[James Brown]

Scott, here you go: NAPA part EP407 rotor.

[Pazuzu]

Originally Posted by wwest

Ignition is firing with the rotor not being close enough to a spark plug "contact" point.

That doesn't look exactly like carbon trails to me, it looks like scratches. The carbon trails I've seen/had were distinct, wormy, and led on to the "hills" where the electrodes were.

Not saying they aren't carbon trails, maybe they look like that after a very long time.

---------------------------
ScottR, if you still have the distributor out, you can test the magnetic pickup. Connect the green signal wire up. Set the distributor on the edge of the engine bay. Connect a spark plug wire to the coil, and put a plug in it (standard spark test rig). You can rotate the distributor shaft by hand (at the gear) and get spark at the plug. Based on that (rotate back and forth, various speeds, etc) you can see if you're loosing any magnetic signals or not. Even slow rotation is enough for the MSD to trigger, it doesn't require much for the Hall sensor to send a signal.

[Scott R]

Originally Posted by Pazuzu

That doesn't look exactly like carbon trails to me, it looks like scratches. The carbon trails I've seen/had were distinct, wormy, and led on to the "hills" where the electrodes were.

Not saying they aren't carbon trails, maybe they look like that after a very long time.

---------------------------
ScottR, if you still have the distributor out, you can test the magnetic pickup. Connect the green signal wire up. Set the distributor on the edge of the engine bay. Connect a spark plug wire to the coil, and put a plug in it (standard spark test rig). You can rotate the distributor shaft by hand (at the gear) and get spark at the plug. Based on that (rotate back and forth, various speeds, etc) you can see if you're loosing any magnetic signals or not. Even slow rotation is enough for the MSD to trigger, it doesn't require much for the Hall sensor to send a signal.

I agree, I just can't find any other answer for why they are there. The rotor looks perfect and I can't find any contaminates in the cap or the pickup sensor area.

The nagging issue is still the miss-fire however, only when the engine is at it's normal operating temperature does it happen. So I've ordered a new coil and I started testing the wires last night. So far they all check out resistance wise.

I'm going to replace the cap, replace the rotor, use some silicone like Steve suggests and get the boots on nice and tight and try this all over again.

[Pazuzu]

It could be the magnetic pickup or the Green Wire. Heat could affect it.


I just went through my own ignition issues, which were solved after some random combination of an MSD box, new plugs, new wires, new coil, new cap and rotor, new signal wire, cleaned up distributor, a serious engine bay ground distribution point, etc etc blah blah blah... Dunno which of those things fixed it but the car runs better than it has since I bought it!



Oh, as for the coil, if you get an MSD Blaster, you'll find that it's an absolute bear to get the Magencor wire on it. The boot is so tight that it creates an air bubble inside, which pushes the wire back off. I put a toothpick between the boot and the coil tower when i install mine, which allows the air to escape. Put the wire on, pull the toothpick out, and you actually create a slight vacuum inside the boot which holds it tight.

[T77911S]

sandpaper marks on the cap. something would break if the rotor was that far off to hit the side of the cap.
make sure both clips are tight on the cap


miss= wires, cap, rotor, plugs, injector/s would be my first pick

[Scott R]

I didn't use any sandpaper on the cap, it's not been off since it was returned to me. Suppose I'll have to ask the rebuilder.

[wwest]

The "burn through" on the coil tower in conjunction with the "scratch" marks inside the distributor tells the tale.

Your distributor is MIS-TIMED internally, with the rotor tip no where near a spark plug connection at the time of the spark/ignition generation the high voltage spark must/will find another jump/arc point.

Matters made worse by the aftermarket HIGHER voltage output MSD system.

Been a LONG time ago but I did once run across a rotor that was too short to have close enough "connection" with the distributor cap spark plug contact.

Strange as it may seem I have also seen a case where random intermittent shorting inside the alternator seemingly resulted in enough electromagnetic crosstalk coupling to the NEARBY distributor's electromagnetic pickup coil that random CDI firing resulted. At least I think that was what was happening, the problem went away with installation of a new alternator. Disassembly of the old alternator indicated multiple shorting points, burned wiring insulation internally under the metal wiring supports.

You are not using an aftermarket high voltage output ignition coil with an OEM or factory standard CDI, right...??

THAT would be the problem...!!!!

And....

Denver...5000 ft elevation....low atmospheric pressure...sparks "jump" easier.

And one more point, as if the above isn't enough.

The output of the factory CDI ignition is not regulated in any way. So if the battery is being overcharged, the 12 volts rising to, say, 16 volts, the nominal 300 volt CDI output rises accordingly, ~400 volts, and the SCR (Silicon Controlled Rectifier) fires prematurely due to voltage breakdown, breakover. Granted, that's an unusually low breakover voltage for an SCR, but not a late 80's SCR. Which is why the typical failure mode of these older alternators, over-charging the battery, oftentimes leads to a CDI failure.