As I was preparing to replace my Spark Pugs and Coil packs (read the article here) to deal with a Lumpy Idle issue with my DB9 (read this other article here) I was researching the Coil Packs to learn if I could find a cheaper source for them. Many of the parts in a DB9 are not bespoke, and rather scavenged from the massive Ford conglomerate parts bin.
Google searching this I came across several forum articles from like-minded individuals on the same search. Some suggested that Coil Packs were the same as a Lincoln LS 3.0l V6 or a Jaguar S Type(both part of the Ford universe back in 2002-2005). In either case, there was no certainty. In fact, they acknowledged that the electronics were likely the same, but the ‘Boots’ that inserted into the cylinder head and internal springs connecting to the Spark Plugs were different, but you could just move the boot and spring from your old one to the new. I was not convinced.
On top of this, there are two generations of Coil Packs for the DB9. Early cars (MY 04 through sometime mid MY05) had 2-pin Coil Packs, and the MY06 and later cars had 3-pin (referring to the number of electrical connectors). I have not found any clear reference to the cutover VIN number in 2005 yet.
I never found an alternate source (either a cheaper aftermarket Coil Pack made specifically for the DB9) or the exact same part sold for another car for less (the Lincoln/Jag may have been similar, but not the same). I gave up and got the Official Aston Martin part number 4G4E-12A366-AA. You can find them online for $66 USD each here, and I paid about £39 ($51 USD) each by contacting Rob Sims at HWM in England. (see my article on Parts Needed to Change your Coil Packs for more details).
After I changed mine out, I decided to disassemble the old one to see if the boots/springs were easily interchangeable, and maybe this would help others find a cheaper alternative. Below are photos and a video showing the disassembly and the result.
- You can remove the rubber boot from the coil pack, and this leaves a wound coil spring exposed that carries the electrical charge to the Spark Plug connection. This spring adds some adjustability to the system.
- The spring is NOT removable from the electronics head of the Coil Pack as far as I could tell. I futzed with it significantly to try and get it disconnected, but no luck. This would be an essential step if you were trying to reuse this portion of the old Coil Packs and marry them to a new electronics head. If you know how to do this without cracking the whole unit open, please share the process with me.
- The spring is specially wound (see the photo) and includes a special area that contains a solid metal ‘core’ that has been inserted. This must play some important role in dampening electrical noise or assisting in transmission of the electrical charge from the Coil to the Spark Plug.
Since the spring/core section is not removable, it seems that if you only interchanged the rubber boot to an alternate part from a Lincoln (that has a shorter stubby body) and maybe just ‘stretched’ the Lincolns spring to reach the same length, you’d not have the solid core or same spring setup. This would worry me greatly that it may affect the performance of the unit in some unanticipated manner – and is not worth saving maybe $20 bucks. It is SOOOOO hard to get in and change these rascals if you do have an issue, the savings would be false economy.
So for now, I don’t know of a better solution. I am very interested to hear your input on this if you’ve got a better solution, or if I missed some detail here. I would love to find an alternate source for this part that was half the price and as good or better.
Check out my video of the disassembly process here, and below are a series of High Resolution photos that might help you in this quest.
Here are some high resolution photos if you are interested in seeing the details close up. Enjoy!