Ignition coils

[oldtuggie]

1976 550 four f1 supersport
Hi can anyone advise me how to use a multimeter  to test a suspected  faulty ignition coils

[Bryanj]

Disconnect the coils then do a resistance(ohms) test between the two small leads and again between the two ht leads with plug caps off, also test the plug caps seperately.
Coils rarely fail but plugcaps do

[deltarider]

Like Bryan said, all suspect the coils, but usually they are OK. Let's take the stock configuration, meaning OEM coils and resistor plugcaps. The coil has two circuits: the primary and the secundary. The primary should read between 4 and 5Ω, so you select the 200Ω range for this. The secundary circuit of the coil itself, with plugcaps removed, should be between 14 and 15kΩ. To measure an individual, disconnected plugcap, select the 20kΩ scale. Each plugcap should read 5-8kΩ. If you read zero, that cap is not the resistor type and then it makes sense to have resistor plugs because you need some resistance in the secundary circuit. It should be resistor plugs or resistor caps, not both. So in total the secundary circuit will be between 24 and 31kΩ. BTW, for that you need the 200kΩ scale. You could start to measure the secundary circuit in total by just pulling the caps from the plugs and then have one probe in cap #2 and the other in cap #3 and for the other in cap#1 and cap#4. As said the secundary resistance inside the coil itself usually is 14 - 15 kΩ. An individual cap's resistance should not be over 8 kΩ. So with the plugcaps connected to their wires, total resistance should not be over (15 + 8 + 8  = 31 kΩ. If it is, plugcaps should be unscrewed from their wires for individual measuring. I'm not fond of R type plugs. Their resistance tend to increase faster than the resistor caps in my experience. You can measure the R plugs resistance by putting one probe to where normally the cap sits and the other probe to the center electrode (a bit difficult but it can be done). When over 8 kΩ, replace.

[JezzaPeach]

Nice one Deltarider, just what I needed too.

[AshimotoK0]

HONDA IGNITION COIL REPAIRING WITH NEW HT LEADS

https://www.dropbox.com/s/x0a4fcpmrwm3l19/Ignition%20coil%20fix.doc?dl=0

[JezzaPeach]

  Nice one Ash too, as I didn’t throw my old coils away and had a DeWalt multi too for Christmas!!

[Laverdaroo]

Gonna have a go at this so that saves me looking for it again, cheers Ash. My leads are so knackered they just hang limp on one of the coils, thought I might have a go after reading ot a few months back.

[oldtuggie]

Thanks for the replies guys, brilliant advice.
2&3 cylinders had stopped firing swapped condensers but it made no difference swapped leads on coils and plugs an 2&3 fired immediately,  I assumed it was the coil never thought of the lead or cap.

[JezzaPeach]

Hi just a question about the primary resistance. I’ve just tested the 2 old coils I had, and 2 new ones now fitted, and on all 4, using 2 different multimeters, the primary ohm reading is zero.
The advice says 4-5 ohms?, I can’t believe the zero readings could be ‘wrong’ on all 4. Any thoughts very much appreciated.

I’ve be doing all the usual checks due to occasionally stalling when hot, and I’m currently also checking for induction air leaks.
(I changed the coils because the leads were poor, and possibly a dud cap was the main issue)

[Bryanj]

Your meter is on the wrong scale or duff

[JezzaPeach]

Strange, both meters show the right ohms for the secondary side.

[deltarider]

The coil has two circuits: the primary and the secundary. The primary should read between 4 and 5Ω, so you select the 200Ω range for this. The secundary circuit of the coil itself, with plugcaps removed, should be between 14 and 15kΩ. To measure [...] select the 20kΩ scale. Which means: after measuring the secundary circuit, you'll need to select the 200Ω range for the primary. Did you?

[JezzaPeach]

Many thanks. I tested a spare resistor plug DR7ES and got around 5 ohms using the 200 ohm scale.
Doing the same on the 2 small coil input leads get zero on each of 4 coils. Very odd.

[deltarider]

I tested a spare resistor plug DR7ES and got around 5 ohms using the 200 ohm scale.
Doing the same on the 2 small coil input leads get zero on each of 4 coils. Very odd.

Very odd indeed, a DR7ES should read 5kΩ. In the 200Ω range it should produce a I, indicating the resistance is beyond the selected scale.

[JezzaPeach]

Sorry I misread your instructions. All clear now. I was confusing the 200 with the 200k
🙄