destroyed coil

[1959LANDROVERV8]

Hi,

Im running a MS-II V3.0 board with 2.892 code.

I am using it to control fuel injection of a 3.9L 1996 V8 Landrover Discovery engine.

Everything has tested with the sim correctly. I am sensing the rev's off the negative of the coil using the opto-isolator circuit. Before connecting the MS-II to the engine harness I installed remove a jumper and installed "D2" a 22V zener with the banded end opposite to what is shown on the silk screen.

Once connected to the engine wiring loom, the MSII powered up properly, and all sensors seemed to be operating correctly. When I cranked the engine, there was spark at the plugs, however the megasquirt did not sense this. I was expecting "cranking" to show up within the Megatune software and the injector LED did not flash on the MS-II box.

I came up for tea, inadvertantly leaving the key on. When I came back 30 minutes later, I found my coil had blown apart and was leaking black goo. Completely destroyed.

I then tested for continuity from the negative of the coil to pin24 of the MS-II. This confirmed that pin 24 of the MS-II was connected to the coil with essentially no resistance.

Looking at the circuit diagram for the opto-isolator circuit. R2 is a 390ohm resistor which is the only resistance between the negative of the coil. Excluding the resistance of the coil itself, this works out to 30mA continiously flowing through the coil for around 30 minutes. Its this enough to cause such damage to the coil? Or is it more likely my ignition module has shorted the coil to ground?

I would greatly appreciate some assistance with this problem as I am at a loss as to why the coil has been destroyed and why the MS-II did not sense the RPM during cranking.

Cheers,

Pete

[1959LANDROVERV8]

We'll immediately after writing this post I had a bit of a brain wave and I was right. The co-axial cable join onto the premade wiring harness was bad which shorted pin 24 to pin 2 just before the computer plug. The solder on the outer shield had melted through the insulation into the center conductor. I will get a new coil and use a crimp type connection this time.

Cheers,

Pete

[trakkies]

Well worth going EDIS on this engine. An easy conversion as all parts are available.

I started out fuel only on my RV8. There was no need to use a co-ax cable for the tach input to the MS - you're talking about a high level signal from the coil of some 40 volts peak.