Does anybody know off-hand what the crank sensor signal looks like? As I recall, the flexplate has two 1/2" holes side by side. So does the sensor show a high, go low on each hole (With a high in the middle), and go back high? Or is it low, hig-low-high and low again?

I'm working on the electrical schematic for the truck build, and since i'm going to be carb'd with an LA block but use the existing cluster (and try to keep the CEL off to pass OBD2 inspection), I need to find a way to emulate the crank sensor.

I can do it 2 ways I think. One way would be to fit a second cam sensor into the distributor with the 4 degree trigger offset for fuel sync, the other would be to use an arduino to interpret the cam sensor and provide a fake crank sensor reading.

A third way would be to use the MSD tach output into an arduino, and emulate both the crank and cam sensors. But I'll still need to know the waveforms.

The crank is a 3 wire with signal/ground/5V and the cam is also 3 wires, signal/ground/5V . Both are thus hall effect sensors with a digital output. I just need to know the output patterns, if there are such.

Right now my thought is to put 8 ohm 5 watt resistors across the fuel injector leads, leave the IAC plugged in but zip-tied out of the way, and plumb the MAP sensor to the air filter hose. I'm not sure what to do with the TPS...If i put a resistor there, I'm sure the computer will throw CEL for engine RPM increase without TPS increase. So I guess I will have to find a way to attach it or a similar device to the throttle linkage.

edit- well I be damned. Youtube does have everything. Looks like yellow is every 2nd blue. Since the dizzy spins half the speed of the crank, i'm guessing yellow is cam and blue is crank, and both have 4 rotors. But if that is the case, I don't see any fuel sync at all, straight up 0 degrees.

Looking in the FSM, it shows the pulses to be given by a 180 degree rotor ring. That does not jive at all to what the video below shows. So if somebody could confirm/deny that, it would be great as well.

 

Cam sensor is used by the pcm to identify what cylinder is what along with fuel sync. It needs to make one complete rotation before the pcm will fire the coil. That's the 180 you see (green line). The crank gets a pulse for each cylinder (blue line). The flex plate has 8 squares cut out for trigger points.

???
I don't think you will get this to work. What about the iac and what the 02's send to the pcm? Even if you do get it to work i think you will get a lot of codes because the pcm doesn't have control of the motor. This will be the first time i seen it done if it does work.

 

So what is the yellow line?

A V8 has 4 spark plug fires per rotation, which is half a rotation of the cam and distributor. So the 180 degree plate on the cam sensor would be high for 4 cylinders and low for 4 cylinders, agrees with the green line.

The yellow line has 2 pulses with the cam high and 2 with it low, which I don't quite understand.

I'm leaving the O2's in place. IAC will stay plugged in, tied up out of the way. Not sure what I will do with the MAP sensor, may plumb it to the air cleaner cowl. I'll build my own TPS more than likely. Put resistors across the fuel injector connections. Keep the EVAP system intact, just plumb it to the fuel cell. Remove the ABS and use resistors to mimic the hydraulic pressure switch and solenoids. Then use an arduino off the MSD tach output to send digital signals to the PCM for the crank and cam sensors. I can program the timings to align to a 4 degree fuel sync signal, and match them up to the pulses from the O2's to align for the prevention of misfire codes. On paper, the computer shouldn't know it's not in control of the motor once I have the tweaks worked out.