Here's your 1st post in this thread...

Changing just the cap and rotor does nothing to change the timing. That only happens when the body of the distributor is moved so that the position of the rotor moves relative to the position of the cap. (And yes, if you wanted to screw up the timing on your truck by moving the distributor, you could).

And your response would be...?

 

Look, I'm sure you're a nice guy and all, but I just don't get what this is all about. What is there to respond to? I think what I said is crystal-clear. I have never "advocated" moving the distributor. Throughout this thread, I've stated that the PCM wants it in a specific place for both spark and fuel.

Yes, I now understand that distributor position is much more critical to fuel than it is to spark:

"Thanks Hahns, that was the best explanation yet, and clears up a misconception that I hadn't quite got past about how the spark can still get from the rotor to the contact inside the cap in a "timely" fashion, even if the distributor has been moved a little. Not at all like my International 392".

Now maybe you can get out of my face.

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Merc, that was a very interesting read, but unless I missed something, it didn't state how the PCM never ever loses track of which injector is next to fire.

 

Winner, winner, chicken dinner!

I suggest some of you buy a copy of the book, How to Rebuild Mopar Magnum V8 Engines.



It was written by one of the engineers who helped develop the Magnum engine and explains a lot of how it works.

 

"My best guess on how the pcm knows the correct firing order of injectors lies in the cam sensor. The pcm sees a disruption of the hall effect and knows that at a specific time after the disruption is registered, fire injector number x".

But, but .... I still don't understand how the PCM "never ever" loses track of which injector gets fired next, for example even after the CMP has been replaced, or if the engine has been turned with the ignition off (eg., 5-speed parked on a hill).

 

You're forgetting the sensor in the transmission that "reads" the flywheel. That's how the PCM knows which injector is firing, and when.

 

This thread:
*facepalm*

 

It's magic.

 

This thread is generating a lot of interesting discussion and beats the shiat out of the usual lazy morons who have to post redundant questions about the plenum, Death Flash, and dash fixes.

 

Hey "facepalm"; tell us how the PCM never loses track of which injector is which, even after the cam sensor has been removed and replaced. How does it never, ever lose track of which injector is which.


"You're forgetting the sensor in the transmission that "reads" the flywheel. That's how the PCM knows which injector is firing, and when".

Do you mean the crank sensor? I'm very aware of what it does; not exactly in the transmission though.

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"It's magic". In other words, you don't know? And the annoyance continues .....

***

Let me try stating another way what I think is a good question.

As I said before, the spark side is easy to understand because the PCM doesn't need to keep track of which cylinder needs a spark; the distributor takes care of that; and the orientation between cam and crank never changes under normal circumstances.

So what happens when you replace your PCM, for example. How does the new one know which injector is which? It just seems to me that for injector purposes, the PCM would need to be told which cylinder is which, at least on occasion.

For those of you who think I'm a complete idiot, tell me (exactly) how the hypothetical new PCM knows which injector to fire.

 

I'd have to say it's all in the timing. The pcm doesn't remember or need a signal to know which injector to fire. The pcm is assuming the timing is right, and automatically activates the required injector. The cam and crank sensors tell the pcm what position they are in for spark, and the programming takes care of which injector to activate.