NON ZR-1 Technical Help needed

[limey]

You guys are smart and i know we have some ECU geniuses here, so i pose my dilemma.

I'm been trying to convert a lamborghini that uses Marelli 3 pin C.O.P. ignition coils to the more common and easy available VW AUDI 4 Pin coils.

For the love of me, i can't get a spark. I switch back to the 3 pin coil and fires right up.

Ive attached 2 pdf pages, the 2002 Murcielago uses Marelli 3 pin, the 2004 uses VW 4 pin coils.

On the 2002 cars, the coil wiring is as follows:

Pin 1 = 12V Power
Pin 2 = Signal Ground
Pin 3 = ECU Signal

On the 2004 cars, the coil wiring is as follows:

Pin 1 = 12V Power
Pin 2 = Signal Ground
Pin 3 = ECU Signal
Pin 4 = Chassis Ground.

So, why when i ground pin 4 on the 2002 retrofit, the car doesn't fire?

[GOLDCYLON]

What happens when you Ground 2 and 4 together or are you running pin 4 to a seperate ground?

[XfireZ51]

Which ECM are you using? And has this retro been done before?

[XfireZ51]

I have a feeling the 4 pin Chassis ground is short circuiting the Signal w the VW coils. Are these coils of equal output?

[limey]

Originally Posted by GOLDCYLON

What happens when you Ground 2 and 4 together or are you running pin 4 to a seperate ground?

Nothing, same no spark issue

[limey]

Originally Posted by XfireZ51

I have a feeling the 4 pin Chassis ground is short circuiting the Signal w the VW coils. Are these coils of equal output?

The VW coils read a LOT higher resistance than the stock ones. I was told that i may need an ignition amplifier, but haven't looked into this yet.

[Paul Workman]

Well, right off the bat, the schematic for the Lambo coils leaves a lot of questions. That and exactly what/how the (ECM) signals the coils: beit a ground or??

And, another thing: If I signal trace the VW circuit and go by the schematics provided, either the schematic for one or the other is wrong, or it is a positive ground whereas the Lambo is a negative ground chassis. Do we know that to be the case? Cuz if it is, it makes a big difference how the switching transistor is biased on, and explains why the VW coil will require some faniggling to make it work.

Note: RE the 4 pin coil: The collector of the transistor switch is grounded, and appears to be a NPN (if the diagram is correct). The emitter connects to (I presume) the battery, and to bias the transistor ON, the emitter voltage would have to be to be negative in relation to collector. That would suggest the chassis is a positive ground, assuming the schematic symbology is accurate. Or, am I missing something?

It may be possible to fanigle the VW coils, but to see what is what, a breakout of the Lambo coil is required; that or taking a whack at guessing how it is configured and experimenting. Do you have one of each in hand? (I'm guessing you do.)

[XfireZ51]

I'm thinking the VW coils are much more powerful than the 2002 coils and so have discrete power and ground. The 2002 ECM likely can't handle them.
BTW, I have read that the VW guys swap in LS-2 coils due to reliability issues better dwell time properties. And of course the LSx coils are 4 wire.

[scottfab]

Very interesting indeed. I've noticed two design elements obfuscated into the schematic which explain why shorting 2 to 4 on the four wire design does not work.
Since this is not a ZR-1 issue for a donation to the club I would consult on the what's going on. Certainly the cost could be passed on to the owner of such a fine automobile.

[geezer]

Kurt; Hope you find a solution for this. BTW still waiting for your parts to arrive here. Check your emails.
Thanks; Bill