Can an EDIS4 coil pack have just one dead tower?

[sgraber]

Here's my setup:

1985 Toyota 4AGE bluetop, MegasquirtI Extra 029q, Innovate LC-1 wideband, Edis4 (coil module and vr sensor pulled complete from single donor at the junkyard).

Here's the background information:

I had a bit of a troubleshooting nightmare when engine cranks but theres no spark on the #1 cylinder. (I am using #1 wire to check for spark since I will use this wire to check timing later.) So I reverse the VR Sensor wire polarity to ensure that it's not wired backwards. Still no spark, but the vr is delivering good voltage. Well guess what, if your coil is not delivering any spark on the #1 wire, then you're going to spend hours re-doing all of your wiring trying to figure out why the VR sensor or the EDIS module are not working! (Because I was trying to get a spark off the #1 cylinder) and megatune is giving me a good reading of RPMs on the realtime display which is showing 266rpm during cranking. Finally I decide to check for spark on some of the other plug wires and I have solid spark on #'s 2,3 and 4, but #1 plug is not sparking. I checked the sparkplug and it's good, I checked the plug wires and they check out too.

Question: I thought that the EDIS coil pack delivered a spark to 2 towers at the same time (1,4 and 2,3) so is it even possible that just one tower would go bad?

The good news is that once I put everything back together and cranked the car (even with just 3 firing plugs) it really, REALLY wanted to start! You know the sound a car makes when the engine is running just a bit faster than the starter? then it falls back on the starter for a second or two and then the engine fires again and just about starts? It is soooo close to running. The laptop shows all of the sensors are online, the wideband is reading a pig-rich condition under cranking, the map sensor is good, coolant temp is showing ambient temperature of 105f as is the Air Intake Temp Sensor. Car shows revs of 260RPM when cranking and jumps up to 700rpm when it tries to outrun the starter, injectors are showing a pulse width... It's all there!

In any case, now I am looking for a new coil pack to get the car running.

Anyone with an extra EDIS4 coil pack they want to sell?

[PSIG]

Question: I thought that the EDIS coil pack delivered a spark to 2 towers at the same time (1,4 and 2,3) so is it even possible that just one tower would go bad?

Yes. Not likely. The EDIS coils function by firing both ends of the coil windings against themselves. This means for anything to spark, there must be a complete current path from one tower to the other somehow. Athough this could happen internally with arcing across the windings, that would not allow plug #4 to fire. The #1 spark must be getting to ground somehow.

This is usually by arcing through the plug wire insulation to a valvecover or something. If the coil surface is dirty, it can possibly arc right from the tower, through the boot, to a mounting screw. You can swap the #1 and #4 plug wires on the coil terminals to confirm this. You can also swap the entire 1 and 4 plug wire sets, but that will change the grounding (arcing) points and might fix it but only temporarily. In that case you need a new plug wire set, plugs or both.

Hope that helps,
David

PS: I check for shorting and arcing in a dark garage or at night. It makes finding stray sparks easier. Be careful!

[sgraber]

I am operating wth a clean coil and new wires. Did as you suggested and no solution. After running a number of tests on the coil that included switching the wires, arc testing each plug lead to the valve cover, reversing the coil leads for packs sides 1 and 2, and testing the resistance of the ht sides to the 5v input and to the triggers I can say definitely that there is a short in the 1-4 tower.

What I see is the #4 tower is getting double the spark energy while the #1 tower gets nothing. And there is measurable resistance from the 1-4 ht towers of to all the pins on the 3-prong plug, the same test on towers 2-3 show open circuit. AFIK I should not be able to measure resistance from the ht side to the input side. I am certain that the windings of #1/4 are shorted internally. I'll have to get a new coil.