So,
1996 vdp engine model 7 4L 112k miles

I've been getting engine lights and the car hesitates on acceleration.
Codes are p0304 (miss on 4) p1314 and p1316 (catalyst damage) and after switching the coil from cylinder 4 to 3 now it's p0303(miss on 3) and p1313.
I assume I just need to replace the coil on top of the plug.
I have a part ordered for $85 from auto zone and I'll let you know if it fixes the rough running issue.

S.

 

Hi Steve i am new to the forum,
just like to offer any help or advice but reading your post it looks like you have diagnosed the fault anyway and hope new coil pack works out ok

ROB

 

Well I replaced the Coil on top of the offending cylinder and all is well There was an area on the edge of the metal wall next to the coil boot that look as if the old coil had been sparking through to the metal. We also cut the exhaust pipe and looked inside at the catalyst to make sure it was ok. It looked fine.
What I did find out was that the codes were telling me that if I continued I could have catalyst damage. NOT that the damage had already occurred. The dealer of course wanted to replace the catalysts....

 

Thanks for the feedback, good to hear your problem was fixed

 

So after the problem happened again and again and in my search of the perfect coil without spending for original Lucas coils I found that the cheap Chinese coils work great if you do one little thing. Isolate them better so they don't spark through to the metal. I started by wrapping them in electrical tape which works great till the tape deteriorates from heat. I have also tried dipping them in rubber (tool handle coating) which works and also wrapping a little piece of rubber around them. All of this works. Even better it seems to work on the OLD heat cracked Lucas coils as well. Just wrap them up so they don't spark through the sides and life is good !!!

 

Hey after getting tired of replacing melting tape I found the following:

Kapton Tape High Temperature Heat Resistant Polyimide

you can get it on ebay and amazon. It has a temperature rating of 200C!!!
Works much better! and doesn't melt..

I am wrapping the coils with about 10-15 layers of this stuff. It is used inside coils and capacitors. It is also used in 3d printers so it is now readily available and cheap.

I have found that my older lucas coils though they don't spark through they don't spark hot enough anymore. but my cheap coils are still running fine with the new tape on them.

Even the tool dip eventually melted and got soft and gooey.
This Kapton stuff seems to work much better.

Steve

 

So after a couple months of hard driving and full temperature the tape on the coils is working GREAT no sparking through. Now I have lost a coil completely due to cheap coil. But NO MORE SPARKING!
This absolutely works.

 

Great tip, Steve.

If I'm not mistaken, Kapton is also used for the voice coil formers in high-power-handling audio speakers, because of its dimensional stability across a wide temperature range. Thanks for reporting back with the success of your real-world trials!

Cheers,

Don

 

check and clean your injectors, it will improve power.

 

[QUOTE=Steve274;435662]So,
1996 vdp engine model 7 4L 112k miles

I've been getting engine lights and the car hesitates on acceleration.
Codes are p0304 (miss on 4) p1314 and p1316 (catalyst damage) and after switching the coil from cylinder 4 to 3 now it's p0303(miss on 3) and p1313.
I assume I just need to replace the coil on top of the plug.
I have a part ordered for $85 from auto zone and I'll let you know if it fixes the rough running

to add more fluid power do have your injector taken down and clean

 

Steve, great find! I have the machine in the barn because of missing. Found exactly as you had, very deep erosion in the ports from coil arcing. I cut some plumber's rubber and was going to wrap the coil with that until I read your post. I ordered Kapton at 40mm to wrap around the coil. How many times did you wrap the coil? I painted the ports with some insulating paint made for battery trays, however do not know how it will fare inside the ports. I made new gaskets and lubed them with dielectric grease. My coils test at about 1.1 on the ohm meter, but have the cracks in the sides. I'll order new coils and wrap them as you did. What do you think about lessening the plug gap to .035? I wonder whether this would have a noticeable effect on performance, it would certainly be easier on the coils.

 

I started wrapping at the top of the coil did about 4 wraps then started winding slowly down at a slight angle when I got to the bottom I did about 4 wraps.
I think the total average coverage was about 10 overlapping wraps. If you do too many it won't fit in the stock gasket. I probably overdid but I've got no problems now. On the bottom I overlapped the edge of the coil just a little so that it wouldn't spark through on the bottom edge.

I don't know about messing with the gap.

 

I don't like not understanding what is happening.
So I'm doing more research on this issue on my own.

With that in mind,
I just got out my dremmel and cut a coil or two apart.
It is a traditional coil like any other car coil.
Two wrappings of wire isolated by an epoxy and a steel core.
There is a metal can around the entire coil.

So from inside out:
Layered steel core
plastic spool
Epoxy
Inner coil with coated heavy gauge wire
Then another plastic spool
then more epoxy coating the fine gauge wire.
Thick layer of epoxy which is grey and not transparent.
Layer of transparent epoxy.
Metal can
Outer layer of plastic.

I tore apart two coils one of the cheap ones and an original lucas.
I cannot see any difference between the two coils.
Thicknesses of each layer seems exactly the same.

I am trying a new new high temp insolation for the coils where they spark through.

It's a self vulcanizing high temp rubber 500deg 8000Volt rating.
I'll let you know how it works.

However I have a new theory and any responses would be greatly appreciated.

The outer can outside the coil is shielded with a thin layer of plastic.
However it is surrounded by the valve cover.
That means that the metal can makes one side of a capacitor and the valve cover
makes the other side of the capacitor.
With the amount of voltage developed inside the coil I'm sure that there's quite a voltage potential between that outer can and the valve cover.

There could be sparking between the can and the valve cover than has nothing do do with the coil itself but simply equalizing the potential. However when this spark occurs it would make a tremendous spike on the ground system of the vehicle.

I found no evidence in the coils I pulled apart of sparking through to the coil.

I spoke with someone else who says that in his experience some people have
many more problems than others and it seems tied to the valve cover.
He said people who replace the valve cover with a new one have no more problems. (of course new ones are almost impossible to find anymore)

That being said. If the connection from coil to spark plug to ground is not good.
either because of bad spark plug, oil on plugs bad boots etc
it will require a higher voltage to make the spark. That higher voltage will make for a greater and longer duration potential on the outer surface/CAN on the coil.
and also make for a different "path of least resistance " for the charge.

So to do some testing I have put some OLD coils that I previously pulled out as known bad back in my Jag. However I have replaced my plugs put new boots on the coils checked the connections on each plug cleaned the surface of the plug hole and for the last 2 days I have had no problems....

I am really tired of buying new coils every 3 or 4 months.

Steve

 

In your previous post#12 you wrapped the coils with Kapton. Are those coils still working properly?

 

The Tape is working I am not sparking through to the side wall of the valve cover.
I just thought I'd try a new one.
That being said. I still have had a couple of coil failures but they are failing internally not sparking through to the sides.
I have painted the inside of the spark plug well with white high temp paint so I can see if I'm getting any additional sparking.

Also I was responding to someone who said in another thread that they were actually capacitors. And if you look at them superficially they do have a metal can outside the primary winding. I wanted to confirm that they were infact coils and that started me on the quest again.

However I've only been running the tape for a few months now.

These coils should last years not 6 months. We won't know how well the tape works till I've had it in here for a year.

Some coils fail by sparking to the wall others fail internally.
So the tape theoretically only helps part of the problem not all of it.

The first problem I have noted with the self vulcanizing rubber is that it is much thicker than the Kapton tape so you have to be careful or they won't go in the spark plug well.

I am very frustrated at why these coils are failing.
This should be a very simple thing.

I have no oil leaks in the wells. I have good boots. I have replaced the valve cover seals/gaskets

AND

The fact that there is a metal can as the outside layer of the coil will make a capacitor with the valve cover. Even if it doesn't "spark" through it could be charging up the valve cover something fierce and cause weird currents on the ground of the vehicle.

Anyone with ideas let's join in here and solve this problem.... There has to be a reason that some people have recurring coil problems and others do not.

Steve

 

FWIW.....

On my car none of the true OEM coils from Diamond Manufacturing have failed.

All (or nearly all.....I've lost track....there have been so many) of the coils from other than Diamond Manufacturing have failed within 6-18 months of purchase

Cheers
DD

 

I cannot find a source for diamond manufactured coils......
If you have one please let me know.

Otherwise I have another question.
Could low battery voltage result in higher current causing the coils to fail earlier?

 

Ok well the Tape works really well for sparking through to the walls of the spark plug wells... however.... eventually the coils break down internally anyway. So it's only making them last just a little longer... I went ahead and bought the expensive coils....

 

Hello Steve,
Any developments in your coil problems/solutions?
Thanks!

 

I didn't see your post back in 2015 but thanks for this interesting info. Is the metal can around the coil connected to one of the windings say at the +12V terminal?