mj1pate

I'm reposting under a new thread now, since trouble shooting has added a little granularity. Thanks all to responding to my earlier posts about "loaner coil wires"

The car starts and stumbles badly, spewing carbon out the tail pipe.
I replaced the (suspect original) final stage igniters today, with no change in behavior.
Using a timing light I see fairly consistent fire on the drivers side bank of spark plug wires during my last check , and inconsistent or no fire on the passenger side wires. I would say this was a slam dunk for coil/wire related issue, but the first readings I took on the drivers side were inconsistent.

Passenger side coil wire resistance: 1k ohms
passenger side coil + to output = 6.5k ohms
passenger side coil - to output = 6.5k ohms

The coil side contacts on all wires look clean. I have yet to pull the plenums and check the spark plug side wire contacts.

what about those resistance readings? Thanks for your help.....

Mrmerlin

swap the coil wires side to side then retest with the timing light

mj1pate

OK; heres an update. The coil resistance reading on the right side is identical to the left.

I removed the passenger side cap and it looked like these pictures.

It doesn't look good for the cap. Yes, I'll order new caps/rotors, but I don't know if this is bad enough to derail ignition to the left side plugs. Should Bosch caps look this bad after 40k miles?

Merlin, I'll ohm out the two coil wires and try a swap, once I get the replacement caps/rotors. (I know I've asked you this... do you fly one of those?)

Mrmerlin

I would suggest that you get a new set of Bosch caps and rotors ,
make sure the rotor is seated onto the pulley,
It also appears that there is corrosion in the mounting holes of the cap,
and the center electrode is bent, this could indicate the cam cover was removed while the cap was still in place thus damaging the cap

also turn the engine over and watch the pulley without the rotor in place see if its out of order.
If someone tossed me the keys to the Mustang I would fly it,
I am a pilot, but never flown a P51

mj1pate

Yes, will definitely do that. While not seeing demolition, all that carbon spewed around looks suspicious.

Do you see that carbon coating on the 4 contacts? That coating is really persistent and resists scraping off. Are the contacts factory coated with carbon? Or is this a build up?

davek9

I've replaced Caps with over 70k miles on them and never seen that, no that is not normal.

Looks to me like a lot of moisture in there(?), also make sure the Cam gears are running true when the engine is running (no wobble).
And if the caps and rotors do not solve the original problem you may want to swap coils too.

mj1pate

update: I just pulled the drivers side cap its carbon spewed as well. Not much difference in the appearance between the inside condition of the two caps.

I live in central Maryland. Is it possible that location has something to do with this kind of deterioration?

SeanR

Well, that doesn't look good. Impressive way to blow up some caps/rotors.

mj1pate

So, to repose my earlier question: are the caps four contacts carbon coated from the factory? or are they solid alloy? Im trying to figure out, without new units in front of me, why my cap contacts seem to have a carbon film on them that is difficult to scrape off.

Further; if the rotor is wiping out some kind of coating on the contacts, then that might suggest cam bearing wear? But the thing is, I would assume that most bearings under tension will cause the rotor to pull in one direction, and not necessarily slice coating off all of the contacts, if they are coated.

mj1pate

Whoa Merlin; I finally took note of this. Yes, some 15k miles/4 years ago, I removed the cam covers and refinished them. No, I did not remove the caps when I did that. I didn't notice any interference at the time during cam cover removal/installation. So, how would interference occur, between removing the cam covers without removing the cap?

Mrmerlin

when you position the cam cover it will usually be off a bit thus having to slide it into place,
Thus the center electrode will also be sliding around on the top of the rotor damaging it.

NOTE when removing the cam cover remove the cap first .

I know its more work, but it will prevent this type of damage..

the metal tips inside the cap are machined metal they look like shiny brass when new. ...

from the looks of the corrosion this engine has gotten put in a wet environment for extended times

NOTE these do not appear to be Bosch caps maybe Bremi,
look carefully the outer black grounding covers are usually swapped over to the new caps.

NOTE the new Bosch caps come with new outer black grounding covers.

using non Bosch parts will usually result in strange damage or wear patterns this looks like it.

Based on the electrodes damage and carbon tracks you also have ignition issues, its probably a good time for new coils, wires ,
and igniters,
ONLY buy Bosch ignition parts and Beru wire sets
Deoxit all the electrical connections

69gaugeman

Those caps are toast. You might try getting in there with a wire wheel on a dremel tool. What do the rotors look like?

The wires may be suspect, in the dark run the engine and see if you see electrical sparks at all. Measure the resistance of the wires. If they are all close then don't replace them just yet. Pull the plugs and see what they look like. Measure the resistance of the plug center electrode to the connection point AND the connection point to the body. Check the large ground strap that connects the engine to the body.

One cap does not do one bank. The wires cross over.

M. Requin

The extent of damage to the caps would seem to indicate the motor ran for more than a few minutes to get to that state. I haven't seen condensation related damage look quite like that - is it possible that some marvelous electron elixir was sprayed into the cap at some point? I'm thinking the PO may have used something like WD-40 or a CRC product or the like. Just a WAG.

mj1pate

I've had the 928 for 7 years now. The PO did the previous tune up and TB/wP job. He was pretty competent and again, that work was done 7 years/35k miles ago. Considering lthe condition of both the caps, and after examining the spark plugs (all carbon fouled), I'm wondering if the ugly caps are cause or just a symptom. The car hasn't been in high water or near a beach. I haven't hosed the engine down, but it was under a car port during a hellatious rain storm we had in the east coast recently. It's been very rainy/humid lately. I'm concerned that once the new caps/rotors/wires are on that it may not improve, but I'll know later this week.

dr bob

First thing to do is clean the crud out of the caps, and burnish the four brass contacts with a soft wire brush. If you have the small rotary brush for your Dremel, use that on the brass. Then thoroughly wash the cap inside and let it dry completely. Then inspect for damage to those contacts.

The center contact is a carbon brush supported on a small spring. It usually sits dead center on the rotor, and transfers spark energy from the coil wire connection to the center contact on the rotor. That pin needs to be able to slide smoothly in and out a small amount in the cap, typically about 1/8" or so total, so it can touch the rotor. If the cap was laterally displaced with pressure on the carbon pin as Stan describes, it can break. If yours is actually broken, it isn't obvious in the picture.

The crud/debris in the cap is interesting, but may easily be timing belt debris rather than carbon from ??? or spattered brass from an arc-flashed cap contact. Regardless, anything in there offers a potential path for spark energy to track to cam cover ground. Clean it all out completely, and you may find that your spark loss is problem is solved.