How do I measure ignition coil resistance?

From
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on Page 10, I can see adrawing of someone taking resistance measurements with a multimeter.

The picture isn't very clear, especially the bottom one (measuring secondary resistance).

Anyone have any photos, or better pictures, of how to take resistance measurements?

Thanks

Michael

Reply to
mrdarrett
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Hold on... that bottom picture on page 10 shows the high voltage wire (removed) in the foreground, correct?

That would explain it...

By the way - how do you remove the ignition coil from a '96 Camry?

Thanks

Michael

Reply to
mrdarrett

The ignition coil is an "auto- transformer". The word "auto" is a co-incidence. Imagine a coil of insulated wire where the first cuople of dozen turns are made from reasonabley heavy gauge wire, then the remaining many, many turns is of light gauge wire, and you have an auto-transformer or ignition coil in the case of a car.

There are 3 connections: the bottom of the coil which is where the pulsed earths are applied from the solid-state ignition module, the 2nd connection is at the junction of the heavier gauge wire with the lighter gauge,.this is battery volts from the key when switched to ON or Start. The final 3rd connection is the spark-lead or HT wire which connects to the distributor center contact in its cap.

The coil works by applying battery volts on and off across the primary or heavier gauge part of the coil. The resulting electro-magnetic flux soaks the secondry or finer gauge part of the coil and a very high voltage spark is developed between earth (battery -ve or chassis) and the spark-lead or

3rd connection.

On older cars, you may have noted the coil also has only has 3 connections ie 2 threaded posts marked "+" and "-" These are the primary which you measure by simply placing an ohm-meter across the 2 posts. The secondry is the HT contact in the coil inslator and "+". The camry coil is the same electrically, but is jammed into the dizzy making access a bit harder.

When mesuring the Camry coil for serviceability, you place an ohm meter across the primary which on a camry is accessible as two soldered (I think) lugs on the coil,..and across the secondry which is across one of the primary lugs (the one which has battery normally on it) and the HT lead out to the distributor. The primary will be very low in ohms, while the secondry very high in ohms. Dont havethe figures on hand tho.

Jason

Reply to
Jason James

Thanks for that. I think my Camry has the coil outside the distributor tho. I know mine has some sort of electrical pickup coil inside the distributor, but I see the high tension wire coming out of a coil near the side of the car.

How do you remove the high tension wire? Press the sides, and pull? Or just pull?

Michael

Reply to
mrdarrett

What year is it Michael? If it has an external coil, it may well be a shape which is not familiar to older car enthusiasts. The easy way to ascertain whether the coil is inside the dizzy or not, is to note whether there is a HT lead attached to the *centre* of the dizzy-cap. If not, the coil is inside the dizzy and vice-versa.

I know mine has some sort of electrical pickup coil

The pick-up coil and reluctor (the star shaped gizzmo which is on the centre shaft) have a critical gap between the star and the pick-up coil. So be careful :-) If you see a component with a HT (spark) lead connecting to a centre socket in the dizzy-cap, you have solved the question, the coil is external.

Once again, the year would help,...with later Camrys eg '90s models, the coil is in the dizzy.

Haven't tried removing the HT leads on my '96, but that clip at the bottom at the dizzy-cap, looks like it needs to be sqeezed, then pulled.

Can anyone else help with this?

Jason

Reply to
Jason James

== California version has the exterior coil.

(larger, less heat exposure). Haynes and Toyota factory service manuals should have procedures for checking resistance though.

Reply to
Daniel

likely to develop problems

Yep, finally got it off.

I got 0.9 ohms for the primary. Spec said should be 0.55 ohms max. Problem?

Secondary resistance is within spec (20 kohms or so, don't have the exact numbers on me at the moment).

So... how do you get the spark plug wires off the distributor?

Toyota sure doesn't make such things easy (removal of spark plug wires, removal of high voltage wire from ignition coil...)

Michael

Reply to
mrdarrett

far less likely to develop problems

Make sure your ohm-meter is "zeroed" when measuring low resistance values, otherwise youcan get large errors. The way to do this is to connect the 2 meter probes together,...the meter should reads 0.00 (zero) ohms. If its unadjustable, subtract any non-zero reading from the measurement your meter indicates for the primary coil. Most cheaper digital mmeters have around 0.2 to 0.5 ohms internal and probe-lead resistance. This would bring that 0.9 ohm reading within tolerance.

Jason

Reply to
Jason James

Great catch! You're absolutely right. The probe / internal resistance is 0.5 ohms.

I got these measurements: Primary-Cold: 0.9 - 0.5 ohm = 0.4 ohm Primary-Hot: 1.0 - 0.5 ohm = 0.5 ohm

Spec is 0.36 to 0.55 ohm cold, 0.45-0.65 ohm hot.

Secondary-Cold: 12 kohm Secondary-Hot: 12.73 kohm

Spec is 9-15 kohm cold, 11-18 kohm hot.

Thanks...

Michael

Reply to
mrdarrett

You don't remove them, it's a one-piece assy.

Could it be Toyota got so many complaints from people using Aftermarket wires that this is a way to try to make them use OEM?

Reply to
Hachiroku

Oh yes... not to mention the "Whoops I put a spark plug wire in the wrong distributor hole..."

Reply to
mrdarrett

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