Harness mod. 98 GT to 2003 Mach1 w/ cops - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 3 Old 02-10-2006, 05:18 PM Thread Starter
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Harness mod. 98 GT to 2003 Mach1 w/ cops

I read an old thread where it was explained how to convert a pre 99 harness w/coil packs to a COP system.

I am doing a 2003 Mach 1 swap on a 1998 gt

Everything is done using the 2003 wiring harness and 98 gt computer. Can the same theory be used to wire the COPs to fire properly with the 98 GT computer and 2003 harness and cops?

How would I do this?

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post #2 of 3 Old 02-10-2006, 08:36 PM Thread Starter
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Sorry, here is the old post by EDO:

"Basically, with the coil packs there are cylinders that get paired together on a common coil. That way there are only 4 actual coils instead of 8, since each 4 post coil pack itself consists of 2 coils. That sounds confusing, but I think you already know what I mean, or look at the coils to understand.

Both cylinders that get fed from a single coil are at TDC (top dead center) at the same time, but only one is at the end of the compression stroke. The other is at the end of the exhaust stroke. The coil fires based on a signal from the EEC and consequently fires both spark plugs. But only one of those is a useful spark creating combustion. The other cylinder fires on the exhaust stroke and this is why it is called a "waste spark" system. That spark is wasted since it serves no real function.

If you look at the coil packs, they are likely labelled so that you can see what cylinders are paired together. Also you will see that there are 3 wires going to each coil pack. One (the center one if I remember correctly) will be +12V which feeds both coils and the others will both be grounds which come from the EEC to trigger the coils.

Now with the coil-on-plug ignition, there are 2 wires for each coil with one being a +12V and the other a ground.

To install the coil-on-plug (COP) ignition, you will obviously have to cut into the harness and do some rewiring since things don't just plug together, but it is rather simple.

For example for paired cylinders 1 & 6:

1) take the positive wire from the old coil pack and run it to the positive connector on the COP coil for cylinder #1

2) run a new wire from the negative connector on the COP coil for cylinder #1 to the positive connector on the COP coil for cylinder #6

3) hook the negative wire from the old coil pack to the negative connector on the COP coil for cylinder #6.

Note that this hooked up the coils in series, not parallel. Then just follow the same method with the other paired coils, keeping the correct ones paired together.

Also, note that there used to be two +12V wires. One per coil pack. You will need to split them since you now need four +12V wires for the new coils.

To those that find wiring in general and this in particular confusing, just spend a little time looking at your stock coil packs and the wiring. All you are doing is replacing the stock coils with new coils and then relocating them on the engine. Just think through it one step at a time. Electrons can be confusing at times, since they are not as obviously visible as a connecting rod attaching to a piston.

Since Anthony may do it when he installs a new 4V engine, the new coils are already in place and have wiring in place. If you are retrofitting the COP coils to an older SOHC engine, then it is up to you to find coil connectors and whether you think it is necessary to bolt the coils firmly in place. I never had a problem with just pressing them onto the spark plug and leaving them unbolted, but that is up to you. You never want to have fuel and air going into a cylinder with no spark taking place or you can melt the catalytic converter".

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post #3 of 3 Old 03-11-2009, 04:55 PM
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