MoTeC Global Forum

In a new M4 installation, whenever I turn the ignition on, all 4 of my coils are firing once.
If there is fuel in the cylinder the flame can go in any old direction, so I am assuming this is not normal!

M4, using LS2 coils. 4cyl, 4 coils, wasted spark, 2 ignition channels.
setup ign = 1
I have no capacitors near the coils, its using the coil harness from the donor commodore(?).

I thought it may have been because my injectors and ignition coils were powered by the same relay powering the ECU. So I added a separate relay as per the Motec diagrams, powering the injectors and coils controlled by the Fuel pump output. It made no difference.

I disconnected the M4 Ign1/2 wires between the ECU and coils, and the spark goes away.

I can do a coil test, both fire as expected. Engine starts and runs.

Noise on ground or ign signals?
Miswired somehow?

I use a different ecu on my LS1.

But this spark you refer to happens in it as well. Under normal circumstances, it does not pose a problem. The only time it make's itself known, is if you have been cranking for a long time with no spark, and there is excess fuel in the cylinders. I'm wasted spark, which makes it worse.

But the only time I actually had a spark ignite anything, was when I first fitted this ecu to the car. It has never been a problem in the subsequent 4-5 years or so.

Not a solution for you, but the problem isnt unique. If indeed it actually is a problem, which I dont see it as.

Just a WAG

I believe my M48 is setup to not fire until I have sync.
I realize this could have down sides as well (like loosing sync in the middle of a session)

However, might this be an option which resolves your issue?

mike

The problem is usually attributed to the coils being powered at the same time as the ECU. Obviously the ECU has a small period of "wake up" time and a coil only needs a millisecond or two to produce a spark. If you have wired the ignition power as we show in our drawings I can only assume you have some type of wiring gremlin.

With it all wired up as per our drawings I would check that there is definitely no 12v to the coils when the ECU is off. Bad earths can cause interesting problems with ignition systems so i would check if there is any voltag drop between the earths for the coils and the earth of the ECU (physical connection to the chassis). Do this first and let me know.