[ace.cafe]

Tom,
Just being curious here regarding a potential UCE twin fireball. Am I correct in my understanding that the crank position sensor in conjunction with the throttle position sensor essentially 'trigger' the fuel injection and spark by completing/switching an electrical circuit.

It could be described that way, but it's a little more complicated than that.
Basically the crank position sensor and throttle position sensor are devices which feed data to the ECU. The ECU monitors these and then actuates control functions based on the data it acquires from its sensors.

The crank sensor is basically a hall-effect magnetic "switch" that is activated as each magnetic pole of the alternator passes by it. So, once the engine is indexed to this crankshaft position during set-up, then it "knows" where the crank is, and how many revolutions it is doing.

The throttle position sensor is basically a rotary potentiometer(variable resistor), that provides a changing calibrated electrical resistance all along its range of movement as it rotates with the throttle plate axle. When the resistance at a certain position is received at one of the analog input ports of the ECU, it then "knows" how far the throttle is open(and the rpm and crank position indicated by the crank sensor), and then it can squirt the programmed amount of fuel into the port by opening the injector valve for a certain time period. The injector operates off a regulated pressurized fuel supply that is kept at a specified pressure by the electric fuel pump. It has an electric solenoid valve to open/close the injector, which is controlled by the ECU. The injector has precisely metered holes in it so that it squirts the fuel in precisely controlled amounts when it is opened.

So yes, they trigger it, but it isn't quite as simple as triggering an ignition spark like a set of points. In the old days of very early fuel injection, they had more simplistic control systems that used switches. But, not anymore.

[ROVERMAN]

Nice Tom, that would be called "hitting the nail on the head".
Robert & REnfield.