Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus

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Sun 26 May 2013 23:03
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - Grimmers

Hi, I'm looking for a little advice. I own a Ford Focus Ghia (Y reg), and yesterday went to pull onto a roundabout and it started driving like a bag of nails. Feels like a misfire - low on power, engine not running smooth and a distinct smell of rotten eggs. I've done a bit of reading on the forums, etc, and it sounds like it could be the coil pack(?)

I've opened the bonnet and figured out where the coil pack is, and disconnected both ends of the HT leads to see if there is any obvious corrosion or bad connections, all connections look fine to my fairly inexperienced eye.

I also watched a video on youtube about 'how to check a coil pack the easy way' which seemed pretty straight forward, so I followed the instructions. Got the following readings between the pins: left and centre 0.8, left and right 0.8, centre and right 1.4. Does that indicate a fault?

I'm looking for help identifiying and hopefully fixing the problem. I have a little bit of knowledge, and a basic tool kit, and I am awesome at following instructions. Is there an easy way of testing a coil pack without getting a new one and trying it? (Not got the funds for that kind of thing). Thanks in advance.

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Mon 27 May 2013 09:40
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - thunderbird

Coil packs are cheap, about £30. Less than a tank of fuel.

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Tue 28 May 2013 00:27
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - focussed

I have tested many coils that read fine on a ohmmeter, but that fail on a coil tester or on the engine. A meter reading is really only a simplistic test that doesn't recreate the real running conditions.

Buy a new coil and try it if it's only £30 a pop.

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Tue 28 May 2013 01:14
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - unthrottled

Focussed is right; multimeter readings are useless for diagnosing coil packs. Often coil packs suffer insulation breakdown when they are hot and when the discharge voltage requirements are highest ie low RPM, high load. So the engine might start and idle perfectly well, and cruise smoothly. But when you plant your foot at 2000 RPM or so, they enginme starts bucking.

Ford had a penchant for very large spark plug gaps at that time. Try closing the electrode gap down to 0.9-1.0mm. If the problem is ameliorated, your coil packs are probably on the way out.

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Tue 28 May 2013 20:47
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - Grimmers

Just as an update - I bought a coil pack from a salvage yard today. Going to fit it tonight when the boy has gone to bed. I'll keep you posted if it fixes the problem. I know second hand coil packs is probably just a temporary fix - but like I said, I'm on a budget.

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Mon 17 Jun 2013 18:03
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - Grimmers

Update. Took about 10 mins to do. Everything working fine once I swapped out the faulty coil pack for the one from the scrap yard. All good. It's been running happy for about a month now.

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Mon 17 Jun 2013 19:35
Ford Focus - How to Test a Faulty Coil Pack on a Ford Focus - Roly93

I have tested many coils that read fine on a ohmmeter, but that fail on a coil tester or on the engine. A meter reading is really only a simplistic test that doesn't recreate the real running conditions.

Buy a new coil and try it if it's only £30 a pop.

Absolutely right, trying to test a coil or magneto with an ohmeter is a woefull and sketchy task at best, as you cannot tell what the coil will do when there is 1000's of volts hitting it. I tend to agree that it is often a gut feeling swap and see activity.

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