I have been fighting with a no-start problem for a while after my truck died suddenly as I was driving down the road. (search on my username for the previous thread on this). The short version is that I have spark, fuel and timing is fine.

I purchased an adjustable spark voltage tester (estimates voltage by looking for a spark between two pointed screws with an adjustable gap). I bought it because while I see a spark at each plug, the spark seemed kind of weak even though the spark from the coil seemed strong (white fat spark from coil). The tested showed that I have a very weak spark at the plug wires - way below the 17-20 kV that it says is needed to start a car. I can't easily use the same tester for the coil voltage.

The plug wires, cap and rotor have been replaced with OEM Toyota parts and measure fine, and the distributor coil resistances and pickup gaps all measure OK. The ignition primary coil measures fine, but the secondary coil measures 6.2k ohms versus the minimum spec of 9 to 15.4k. I checked this value with two multimeters to be sure.

It looks like some of the windings may have shorted out, resulting in a lower than normal voltage.

Do you guys agree? I'm looking for some other opinions before I invest in a new coil.

Since everything else has checked out to be with in specs or has been replaced with new, the secondary looks like the problem. Less than 3ohms doesn't seem like much, but anything outside the specs is bad.

You might check your local wrecking yard for a good one, before plunking down the $$ at the dealer for a new one.