This folder contains all combinations of wiring options for Coils. The main choices are, no of cylinders, basic or built-in driver coils, wasted spark or COP coils and the type of spark required namely Distributor, Wasted Spark or Full sequential spark. Each folder contains its different variations for your engine. Note that the drawings are generic and you have to dill in your own firing order to see which wire colour goes to which coil. Print the document and write on it before you begin.

Abbreviations in this section.

F/S – Full Sequential
W/S – Wasted Spark
COP – Coil On Plug

See the sub folders more information.

Mercury Coil Drivers

Ignition Coils

Distributed Spark System
With this system, which was popular in the older cars, there is only one ignition coil for all the cylinders. The spark is distributed to the spark plugs with a rotor and distributor cap. Here only one driver is required from the ECU. The disadvantage of this system is that the coil has to charge and discharge a couple of times in one revolution. With high revving and performance motors this means that spark quality will deteriorate with increased RPM’s. Another problem is spark deterioration with the gap between rotor and cap. It also has a higher maintenance service. Very important for these systems is the rotor fazing. Advantage is one coil and driver and full sequential spark system. (View it further in the manual.)

Wasted Spark System
With this system there is one coil for the two cylinders that move up and down simultaneously. The cylinders that are 360 degrees apart are paired. These coils have two High Tension towers which spark on the two plugs simultaneously, one on compression stroke and the other on exhaust stroke. Each dual coil is being driven by its own driver in sequence from the ECU. The advantage is less drivers and coils and better spark than distributors. This method only requires a crank gear with TDC slot. Disadvantage is the coils energy is divided between 2 spark plugs. Also the fact that current is reversed through on plug. This deteriorate copper cored sparkplugs unevenly.

Multi Coil Spark system
With this system there is one coil for every spark plug. The coils must be driven by separate drivers from the ECU. This makes the ECU larger and more expensive. The coils are fired in full sequential or wasted spark method. The advantage is more spark energy per cylinder. Disadvantage is the number of coils and drivers required.

Different Types of Coils

Coil Selection
It is important to know which coil on the engine has a faulty setting as this may destroy the ECU driver or coil. Always start the ECU with a disconnected output connecter till you set the trigger level output to the correct setting, or alternatively wire the ECU correctly. Start with a 5A Fuse in the coil positive circuit which will blow quickly if you have an error. If you have coil packs with a common positive, insert 5A fuses in each driver signal to protect the coil against damage.

Oil filled coils
The point-condenser coil has a resistance of +/- 1.5 ohm and a charge-time of 7 m/s. the spark on this coil will be weak. Should you need to use it do not connect the ballast resistor. If the coil has a resistance of 3 to 3.5 ohms it has a built in ballast resistor and will produce poor spark. It is not recommended to use these coils.

Electronic ignition coils were designed for variable dwell systems to improve spark at high Rpm’s. They have a resistance of +/- 0.8 ohm. and a charge time of 3 to 3.5 ms. they can be used effectively but are being phased out by manufacturers. Some coils go as low as 0.4 ohm and need charge times of 1.5 to 2ms. For these coils Mercury2 must be used with the Mercury Coil driver.

Epoxy filled Basic coils
These hard resin coils and consist of single, wasted spark, COP or combinations of coils in a single housing. Some have built in driver electronics. If it has no driver there is usually a common pin and one pin for each coil. To measure this coil put the meter on Ohms and measure all the points. You should get a 0.8 Ohm reading for each coil. If you measure over the two coils it should read 1.6 Ohm. For these coils Mercury2 must be used with the Mercury Coil driver. See the Mercury Coil Drivers.

Epoxy filled coils with built in drivers
If you measure high resistances on open circuit, then the coils have an internal driver. These coils normally have a positive, ground and trigger input for each coil. These coils are normally charged with a positive pulse and fired with a negative going pulse. Mercury2 can drive these coils directly. These Coils with internal drivers can be connected two coils per output. You must make sure on the firing order to connect the two cylinders of these coils that move up and down simultaneously.

Spark Plugs and Leads
Use high quality inductive suppression leads such as Bougi Cord. Don’t use wire leads: Possible interference.
Be careful when changing spark plug type. Always consult the vehicle’s owner’s manual first. Some ignition coils are sensitive to the type of spark plug used. If the ignition system uses resistive type plugs from the factory NEVER use non-resistive plugs as it may result in coil failure.
Run high tension leads as far from the ECU wiring as possible (especially sensor signals). Otherwise reconsider the wiring loom and layout. If the loom must cross the ignition wiring it should do so at 90° angles to minimize the interference.

(See the sub folders for explanation on wiring and connections.)