coil resistance problem
 

I am still trying to resolve a no spark problem. My coil is reading out of spec on one of the resistance reading. Clarks garage and Haynes both say that the resistance between the pos. and neg. should be .4 ohms to .6 ohms, mine reads .9ohms. So, logically it is bad and should be replaced. I ordered another coil from ebay, a used one in good condition. That one also reads .9ohms. I might have done something to it, i don't know. What would cause a higher resistance reading than normal? How does that happen? Do I need another coil?

Here is another explanation on coils.

Ignition Coils

I checked my coil a minute ago (waiting for Pelican ICV hoses) and I got a reading of 1.9+-ohms. The car ran fine and no starting problems.

It could be the coil but since you have a spare and the readings are the same---look elsewhere for the no spark issue.

GL
John

Did you allow for the resistance of the meter leads? That is usually around 0.5 ohms on a typical meter. Older analog meters have a zero adjustment while modern (budget) ones do not. Short the lead probes together on the lowest resistance range. What does it read? Then deduct that reading from any measurements made. Is that better?

The coil is often unnecessarily blamed while they are usually quite reliable. More likely is another cause, such as DME relay or crank sensor.

In the same vein, the cheaper meters, and even some more expensive ones are not always very accurate at readings less than an ohm. Also, the reading you get depends on decent contact through old oxidised surfaces, so believe the true reading will always be the lowest one you got, or less.

cheers
R

To test the coil, connect a spark plug directly to it and ground it. Disconnect the (-) lead from the coil, turn on the ignition so the (+) terminal has 12 volts on it. Connect a piece of wire to the (-) coil terminal. Then with the other end stripped of some of the insulation, lightly scratch the bare wire over some grounded metal on the engine, and you should see the plug do some sparking.