[Macroblock]

The stock ECM provides an injection delay of 1 or 2 seconds, which is not nearly enough time to prime oil into the LT5 engine. My inclination is that it would take closer to 30 seconds to prime and pressurize all the oil passages with a typical start-up crank of less than 400 RPM.

As I reverse thru the functions of the Engine Control Module (ECM) and the Direct Ignition Module (DIS), here are my observations.

The original starting process involves a fuel injection delay merely to allow the Ignition Module to synchronize with the crankshaft and to allow fuel pressure to build up.

When the engine is turned over, and the DIS is satisfied with the signal it's getting from the crankshaft sensor, it generates successive signals to the ignition coils and provides a stable 0/5 VDC square wave to the ECM on the Crank Reference line (D18). This square wave signal will change states 8 times per crankshaft revolution - this equates to 4 complete pulses per revolution.

Once the ECM sees an appropriate number of Crank-Ref pulses per second, it energizes the fuel injectors and in due course the engine starts.

This means the engine normally doesn't receive fuel for the first second or two after cranking begins.

To improve starting, my firmware injects fuel, when appropriate, before the DIS energizes the coils, which means the engine will come to life sooner.