159 3.2 V6 Blowing Coil Packs #4 again and again and again

[alfagtv100 (Biggus)]

Hi all,

I have searched the forums for posts dealing with the tricky #4 coil pack destruction issue.
On a couple of occasions, a blown coil pack has caused fuses to blow.

The posts (on Alfaowner) I have found offer endless suggestions. The most promising (fingers crossed) seems to be:
- "Ultimately to resolve melting coils I dumped Bosch plugs and went for Denso 4719 Iridium ITV20TT (no need to gap them) - 0.4mm diameter centre electrode."
However, I am sceptical.

What I wanted to ask the community is, are there any members who have successfully resolved this problem? If so, could you please reply with details of what actually fixed the problem?

So far my (very good) indie has tried:
- Coil packs. 3rd party and Bosch. For all six cylinders.
- Spark plugs (unfortunately, I don't have make/type info)
- All wiring checked by an auto-electrician - twice

This post may possibly help some other poor souls in the future, so if possible, please reply with confirmed resolutions only. No suggestions. They have already been shared.

Cheers guys

[105gta]

Ok trying to make sense of your post. So is it just cyl No.4 that keeps killing coils?

[alfagtv100 (Biggus)]

Hi 105gta,
This week, coils 4 and 2 blew, but over the last 2 years, it was coil #4 which blew.
Cheers,
Marco

[105gta]

Hi Marco, sounds like you have an earthing issue I'd recommend getting the car along to a good diagnostic auto electrician. Not just a regular auto electrician. I would even try running new earth wires for each of the coils. And the main engine earth to chassis and battery should be checked/cleaned
Ben

[alfagtv100 (Biggus)]

Hi Ben,
Thanks heaps for the suggestion.  The car has been checked by an auto-electrician, but I don't know if he is a guru.  I will find out.
Cheers mate,
Marco

[Colin Edwards]

Hi Marco, 
A common plug shaft / connector ignition coil failure mode is as follows:
One fails and is replaced and some time not too far in the future it fails again
ANY other coil that has been removed and inspected or swapped with a known good one to eliminate rough running also fails not too far in the future

End result is a number of failures - usually burnt insulation or melted plastic due to overheating coils.  The root cause of this is usually over-tightening of the fixing screw or poor seating of the coil connector on the spark plug insulator. 

The correct torque is usually around 6 Nm.  You will rarely see anyone using a torque wrench to tighten these bolts!  The over tightening causes the coil housing to crack and damage the coil winding insulation.  The coil flashes over internally, burns insulation and melts the plastic housing.  The coil finally goes open circuit and the engine develops a misfire.

When plugs are changed or the plug-shaft ignition coils are swapped about for fault diagnosis, the plug insulator MUST be lubricated with a special high temperature spark plug connector grease.  This allows the plug-shaft ignition coil to slide over the plug insulator during assembly and disassembly. 

Most of the damage and resultant failure is due to incorrect disassembly / reassembly procedure.  This problem is in no way peculiar to Alfa Romeos!

[alfagtv100 (Biggus)]

Hi Colin,

Mate, I have to thank you for the best explanation of what could be causing the issue I have read, after much consultation of the book of Google.
Thanks very much for taking the time.  If you are right, I owe you a BIG drink.

Cheers,
Marco.

[ACE]

Colin,
+1 for the excellent explanation.
Could you please elaborate on the high temp grease for the plug insulators ?
What is it and where can it be sourced?
It sounds like it should be in every home mechanics kit.
Thank you,
Peter.

[bazzbazz]

More commonly known as "Spark Plug Boot Grease" or Dielectric Grease.

Available at most auto stores.

[Colin Edwards]

Hi Ace,

The lubricant / grease is a silicon based high temperature dielectric.  NEVER use ANY grease other than the proper stuff.
Permatex Dielectric Grease I have was probably purchased from Bursons.  I have seen it for sale at Autobarn. 
If you go to the Permatex site the part # should be listed there.  Seem to recall its about $15 < $20 a tube.  USE SPARINGLY and follow the instructions to the letter!
Also pays to have in you tool kit a 1/4" drive high quality torque wrench.  Purchase one with the shortest arm possible. 

Coil pack pullers are available however I have never seen one in the flesh.  BOSCH probably do one to suit the JTS coils.  The puller is unique to the coil design.  Fair chance one could be purchased as a GMH service tool?

[ACE]

Colin & Bazz,

Thank you again.
My approach with all of my pre-coil pack cars has always been to ensure that the spark plugs are clean and dry when assembling, so this revelation is somewhat counter intuitive!
So I'll be off to the shop soon for the proper stuff as it will likely be needed this weekend and maybe another torque wrench to add to the collection too.
Ciao :-)

[bazzbazz]

Ahhhh, one other thing, I just happen to be talking to a fellow Alfa mech today and he was working on a JTS engine and noticed that half of the coil packs were 5mm too short!!   

As the car uses the same spec coil as the same period Commodore, (They are both GM bases engines) I suspect they may have been accidently replaced with the incorrect length coil from a different manufacturer but gotten the wrong part.

On your car check the length of one of the original unchanged coils with the length of any new ones.

You never know.

Check Six

Baz

[Mick A]

On the GM based 3.2 V6 JTS, the cylinder numbers aren't the same as an Alfa Romeo built V6. It goes from drivers to passenger side on the back head 1,3,5 and on the front head 2,4,6.

Thought that might be useful info just in case you didn't already know.

Mick.

[Craig_m67]

I always thought number one was the closest to the flywheel .. Shirley if they're the same block (Alfa/GM)...?

Not doubting, just wondering

[Mick A]

When fault finding on a customers car many years ago I removed the coil plugs one by one to check which error came up on the scan tool, and worked it out that way.