4.2L crank + aftermarket cam= ??? in setting cam sensor

[Retlaw01XJ]

Any idea how the stock PCM works?
Does it maintain the 'end injector close point' and just open the injector earlier to richen the mixture? I believe that's how the Megasquirt works. (??)
There's no point in keeping the injector open past the intake closing point...but opening the injector before opening the intake valve isn't a bad idea....the fuel stays in the port absorbing heat which actually helps it to atomize.

Maybe I should just put a carburetor or my '01..... at least I cold understand how it works!

[SilverXJ]

I don't know exactly what the PCM does when adding fuel, but I was measuring the closing point with the timing light as the kick back comes when the coil closes. Maybe the opening point is what stays constant and the closing is moved. I suppose I could hook an oscilloscope up to the #1 injector and the CPS and see what happens(would be able to measure opening point), but I am not sure how much voltage is being fed back to the PCM when the injector closes. If its too high i could fry the oscilloscope.

[Sharp Rock]

I suppose I could hook an oscilloscope up to the #1 injector and the CPS and see what happens(would be able to measure opening point), but I am not sure how much voltage is being fed back to the PCM when the injector closes. If its too high i could fry the oscilloscope.

SilverXJ,

You could add a small wattage (like 1/4 or 1/8 watt) high resistance resister in series with the probe. Maybe start around 1 to 5 meg. Then decrease the size until you find the range you need. A variable pot would work too if a large enough range was on hand.

[RayRay]

what i done with my titan4.6 was what the factory manual stated about tdc timing marks alined and all. well it ran good but was 23* advanced. had jeep dealer put the crank and cam sensor in synk.