I hate it when this happens: you think you’ve seen something but you can’t remember what, or where, or how……
I’m trying to remember if I’ve correctly remembered something Paul once said in a video, and, if I did, how it can possibly work.
It was to do with a long crank time because the crank sensor had failed, but the ECU then looks at the signal from the camshaft sensor instead and uses that input for rpm and firing/injection timing. Now, if I didn’t dream all this, and there was such a video (or videos), what I would like to know is how, without missing teeth to provide a datum, can the ECU use camshaft signal and know when the right point in the cycle is to inject and ignite?
If anyone remembers such videos, and can provide a link, I’d be grateful. Alternatively, if I need to be told I simply had a bad dream and it isn’t possible, I’d also be grateful.
The crank can only give you two things, rotational speed and position.
Without any specific ID tag like a missing tooth, it can only give speed. But even with that missing tooth, it cannot tell where cylinder 1 is supposed to be firing, as there will be more than one cylinder at TDC at that point ( 4cyl or more engines )
Whereas a suitable camshaft trigger, even a single tooth can give all the data, albeit slower and with less resolution, but because it can positively identify cyl1 compression stroke.
But running like that is certainly not ideal but would be a get you home strategy.
Of course it does require a suitable. eg, 4 equidistant identical teeth would not positively identify cyl1 alone. But with the right number of cylinders, it might just denote that every tooth could be an injection/spark event sufficient to allow the engine to run.
There are lots of options and variables, but in the absence of either a crank or cam, with the correct tooth pattern, one can quite easily allow the engine to run.
I think I remember a video covering that as well?
I'm pretty sure the explanation given was that the PCM will fire injectors/coils in pairs untill the engine is running, hence the long crank time.
If I can find it, I'll post it up here.
man, I'm so sorry I am late with this, but here is the video.
It was a bad engine computer in part 1 and when it came back it had a long crank time and a crank sensor code (I left it unplugged when I was testing it in part 1 I think)
