Ignition coil boots for Ford V8 (SOHC) and V10 engines
with 'Coil-on-Plug' ignition

What is coil-on-plug ignition?
Many newer engines (from most auto manufacturers) have an ignition system that is commonly known as a "coil-on-plug" or sometimes "coil-over-plug" (or COP) ignition system. These systems connect a separate ignition coil to each spark plug without the use of spark plug wires. A typical setup for each cylinder consists of an ignition coil bolted to the valve or cam cover of the engine, which is then connected to each spark plug with some sort of connector. The designs of the ignition coil and connectors vary from system to system, but with all COP ignition systems, there are NO spark plug wires.

The COP assembly for Ford V8 (2 valve per cylinder) and V10 engines:
This page specifically refers to COP ignitions used on US Ford 4.6 liter V8 engines (many engines from 1997-2002), 5.4 liter V8 engines (most engines from 1997-2002) and 6.8 liter V10 engines (all engines) that consist of:

• Ignition coil for each cylinder - which is bolted to the cam cover;
• Spring/suppressor assembly for each ignition coil - which connects the ignition coil to the spark plug and provides some noise suppression;
• Insulator boot that fits over the spring/suppressor assembly - that is intended to seal the spark plug well and spark plug itself from moisture (see photograph, below).

For V8 engines, this assembly is only used on the SOHC (2 valve per cylinder) engines, and can be identified by the obvious lack of spark plug wires. Some DOHC (4 valve per cylinder) engines have COP ignitions, but these have a different design.

What is the problem?
(See photo below). Often, particularly on high mileage engines, driveability problems such as missing or hesitation become evident and sometimes a costly ignition coil will fail. 

These problems occur because of  the overall poor design of the cylinder head and coil assembly, which doesn't take into account that moisture will inevitably end up inside the spark plug wells. These engines had similar problems when spark plug wires were used and the solution was to replace the spark plug wires, or even a single wire, but he use of coils-on-plugs will cause consumers to pay 10 times as much to fix the same problems.

Generally, the rubber boot used to insulate the connection between the coil and spark plug is first to fail. The seal of the insulator boot at the cam cover is not adequate (due to poor cam cover design) which results in moisture seeping in and around the spark plugs. The moisture, when combined with the large factory spark plug gaps (which are at least 0.055" or higher, and get worse with age) causes sparks to ground out on the cylinder head, rather than across the spark plug gaps, which results in failure of the insulator boot. Once the boot fails ignition coil failure is not far behind since it becomes overloaded by the excessive voltage grounding out on the cylinder head.

A photo of the complete Ford ignition coil assembly, showing a typical boot failure.


How to solve this problem:
The problem cannot be 100% solved, since it is related to poor cam cover design, but replacement of the damaged insulator boots can go a long way to solving driveability problems and ensuring that you do not have an expensive ignition coil failure. Up to now, the only solution from Ford has been to replace the complete ignition coil assembly as shown above - which includes ignition coil, spring, suppressor and boot. Magnecor does provide a solution to this problem, we can supply the correct factory insulator boot. If this boot is replaced in time you may save failure of your expensive ignition coils. We recommend that spark plugs are checked, and replaced if necessary, at the time you replace the boots.

Please understand at this time it is not known how many engines will suffer this problem, but if you are experiencing missing and hesitation (particularly on a high mileage engine where you have not changed the spark plugs for a while) then you may need to replace these boots. If the ignition coil has been damaged, due to being overloaded, our boots may not stop its ultimate failure.

IMPORTANT NOTE: As you will observe, because of thoughtless engine design, replacement of these coils, boots and spark plugs is an extremely difficult and time consuming operation that may be beyond the skill of many people who are not trained mechanics - therefore it may not be a good idea to attempt this operation unless you are confident of your skills and have the tools and time to do the job. If you feel you may have a failing ignition coil boot you may want to contact your mechanic to check and/or replace the boots, and inform him that he can purchase the insulator boots from us.

Replacement of suppressor:
The ignition coil assembly also includes a noise suppressor, which is a resistor. It is possible that the suppressor will fail over time and also cause ignition problems, however we currently cannot supply this component.

Part numbers and prices:
The insulator boot we supply is the exact factory part (see photo above, except it is in new condition). The following prices are retail prices only, trade/wholesale dealers should contact us for pricing. There is no minimum order or quantity.

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