318 stalling while driving
The 5th wire on original factory ECUs was a part of the internal power control. Later the factory and aftermarket was able to incorporate solid state control into the units without using that. The 5th wire is just along for the ride and available if you ever install an original ECU.
The ECU draws only a little power as all it does is amplify the magnetic pulse (wires from the distributor).
That amplified magnetic pulse signals when to make and break the primary coil circuit. Its just an electronic version of points opening and closing.
When the key is in run, the power available in the J2 wire is approximately 14 Volts (engine running).
The coil doesn't need power supplied at 14 Volts. It will draw more current and get too hot if given power at that voltage. So it draws power through the half ohm resistor. This reduces the voltage the coil sees while running to something less than 14 volts..
The 5th wire on original factory ECUs was a part of the internal power control. Later the factory and aftermarket was able to incorporate solid state control into the units without using that. The 5th wire is just along for the ride and available if you ever install an original ECU.
The ECU draws only a little power as all it does is amplify the magnetic pulse (wires from the distributor).
That amplified magnetic pulse signals when to make and break the primary coil circuit. Its just an electronic version of points opening and closing.
When the key is in run, the power available in the J2 wire is approximately 14 Volts (engine running).
The coil doesn't need power supplied at 14 Volts. It will draw more current and get too hot if given power at that voltage. So it draws power through the half ohm resistor. This reduces the voltage the coil sees while running to something less than 14 volts..
