Setting Timing

[Gaz64]

Originally Posted by Bernica

No way they could be touching. Two hard parts (rotor tip and plug contact) rubbing together? They would either clearance themselves or break something.

That's correct.

[Bernica]

Change to a new cap AND rotor and try it. Another option is to borrow a working dizzy from someone and try that as well. Is your dizzy gear in good shape? Running out of ideas....

[patrickt]

FWIW, here's a closeup of my rotor tip. I think they start out touching and he has a new rotor and cap. But I don't know....

[Large Arbor]

Yes, I am still apt to think I have a component issue and leading towards the coil. I will talk with MSD tomorrow and get some advice. Just bizarre issues to have two cylinders firing and nothing else. That kind of bothers me. I did not re-wire anything. The car has set and not moved. Not sure of what is going on, but I will get to the bottom of it.

Phil

[Gaz64]

Originally Posted by patrickt

FWIW, here's a closeup of my rotor tip. I think they start out touching and he has a new rotor and cap. But I don't know....

Patrick,

That is normal "burning" of the rotor tip as the spark arc jumps the gap, not from metal to metal contact.

[Large Arbor]

Mine looks brand new...

[Gaz64]

Originally Posted by Large Arbor

Yes, I am still apt to think I have a component issue and leading towards the coil. I will talk with MSD tomorrow and get some advice. Just bizarre issues to have two cylinders firing and nothing else. That kind of bothers me. I did not re-wire anything. The car has set and not moved. Not sure of what is going on, but I will get to the bottom of it.

Phil

Hi Phil,

I have never heard of any V8 ignition system only firing on two cylinders.

Have you performed the MSD spark test, by jumping the mag pickup harness with a paperclip?

What is the quality of the spark, color and gap jumping capability?

Can you measure the pickup resistance with your meter?

Gary

[Gaz64]

MSD are known for rotor phasing issues, and the burning on yours shows that.

I would also look under the rotor button where the terminal screw is to see if the spark is going straight to ground.

[Bernica]

Originally Posted by Gaz64

Patrick,

That is normal "burning" of the rotor tip as the spark arc jumps the gap, not from metal to metal contact.

That is correct. I used to rub the tip of the rotor down with some steel wool from time to time and use emory cloth to sand the faces of the contacts in the cap to ensure a good arc.

[Gaz64]

Originally Posted by Bernica

That is correct. I used to rub the tip of the rotor down with some steel wool from time to time and use emory cloth to sand the faces of the contacts in the cap to ensure a good arc.

We've all done that, I learned to do that as a young mechanic.

Believe it or not, a small corrosive buildup on the terminals is still a better conductor than air.

So scraping terminals is a no-no. More frequent inspection and replacement of cap and rotor is the go.

[DanEC]

You might check continuity of your rotor from center contact to rotor tip. I never heard of this until the other day but I read where someone found a rotor that was very high resistance between the two - should be near zero.

Hard to see how a coil could cause your problem - it feeds the cap but doesn't have any way of knowing which cylinder is next in line to fire.

I can't see how you can even get the motor to run on two cylinders (?) That sounds unlikely - more likely would be most cylinders are firing but getting a weak spark. Did you use your timing light to check each cylinder to see if it flashed, indicating power to the wire? Since you have had the plug wires off and on so many times I would check each one out for resistance and while checking them be sure to move the wire around at the plug boot. Some types of wires/connectors can be damaged pretty easily at the plug boots. Also push the plug boot back if you can and make sure the terminal is still securely crimped to the wire.

[patrickt]

Originally Posted by Gaz64

MSD are known for rotor phasing issues, and the burning on yours shows that.

I would also look under the rotor button where the terminal screw is to see if the spark is going straight to ground.

I remember Kirkham's nice thread on that. MSD Rotor phasing But wasn't LargeArbor's engine running properly at one time? Something, somewhere, broke on it.

[1795]

Phil,

I would agree with Dan, and the others in that you should check the wires, cap and I would also suggest the spark plugs. Dan is probably correct in that some of the time the other cylinders must be firing, the engine would not run on just 2 opposing cylinders very well. It wold sound like my fathers old 2 cylinder John Deere tractor, chug, chug, chug, chug. What may be happening now is that since there have been multiple attempts to start then engine with little or no electrical output to the spark plugs, most of the spark plugs are probably fouled. Get a new set of plugs and try them as well. Also, there is a gap between the rotor and contacts for the spark to jump across. Maybe the cap is bad in that the contacts for the most part are recessed too far? Can you take a micrometer and measure the distance from opposing contacts and see if there is a difference? If the gap gets too far the spark will be weaker and possibly non-existent.


this is a baffling problem, there are very few scenarios that would result in only 2 cylinders firing, and even those situations are basically ruled out. If the cap were out of round, you might get a situation where only the 2 contacts that were opposite each other and closest to the rotor would be the only ones able to get spark, but your 2 contact points are right next to each other. The only way that the coil would be implicated is if it was sending weak charge to all cylinders, which is not your case (unless all of the plugs are getting fouled and these are just the last 2). A bad rotor would not be bad on only 6 of 8 contacts.

I just am not knowledgeable enough about computers to know if the programming in the MSD could be off and only allowing spark to go to 2 cylinders, but that does not seem likely.

[DanEC]

I forgot about the two cylinders Phil believes are firing are consecutive in the firing order. That means out of 720 degrees for firing all 8 cylinders, it's only firing on 180 degrees of that and the other 540 degrees are just coasting. I don't think that's possible unless the engine rpm is elevated way up there first.

[Large Arbor]

Gary,

Yes, I did the MSD spark test and had spark.

Patrick - Yes, the engine was running well last week prior to the pushrod episode.

Continuity at the rotor button to cap is fine - checked that last night.

Phil

[Large Arbor]

Dan,

Only the two header tubes were hot so only two cylinders were firing. Any chance the distributor cap could have been turned 180 degrees from where it was supposed to be?

I am still scratching my head on this as well.

Phil

[DanEC]

I still tend to believe you are getting a weak fire in a bunch of cylinders (still be relatively cool on exhaust and maybe no fire or one or two. I would ohm all the plug wires and check for high resistance and loss of continuity in them.

[Large Arbor]

Dan,

Completely agree with all of what you guys are saying and am not ruling anything out. I also plan to talk with MSD.

Phil

[Grubby]

Large,

I have been watching this thread and thought I should throw an opinion in.

I would use a spark tester or home made version, to test spark on each cylinder. If you get a new spark plug and put a small house clamp around the threads then clip a ground wire to it. Gap the plug to about .060".

Plug the tester into each plug wire with the ground wire attached to the plug and to a good ground. Crank the engine and look at the spark. I would expect a nice blue spark on each cylinder. This will test your complete ignition system.

John

[Large Arbor]

I bought a new cap and rotor button and will start there. I will check to see if I cam getting spark at each wire and then go from there. I think this is the only way to know whether it's a good spark or a no spark situation. More to follow tonight.

Phil