Flexplate

[Dando]

4 minutes ago, HOrnbrod said:

Yes, it will tell you the advance or not from TDC, and also if it's flaky (jumping around) or not. Suggest you invest in a decent timing light.

 

I can work on getting ahold of one. Still curious what this will tell me. It ran before the flexplate broke and now it won't run properly. If the timing is not adjustable I guess I don't see how it could just suddenly be off (need to be explained) and if it's off how could I fix that if yet again it's not adjustable. 

 

Would the timing light just confirm if the flexplate is my issue? And if so, how? 

[DirtyComanche]

21 minutes ago, Dando said:

 

Would the timing light just confirm if the flexplate is my issue? And if so, how?

 

The windows in the flexplate are what the crank position sensor reads, and that's the basis of how it determines when ignition and injection events are to occur.  Obviously ignition advance/retard is modified beyond that baseline depending on the output of other sensors, but those windows and the crank position sensor sets the base timing.  If those windows are screwed up the timing will likely be hunting, or way advanced or way retarded.  As I previously mentioned, the one my friend had refused to idle properly as the timing was going amuck at that point, but his issue was that the windows in the flexplate were the wrong size, if they had simply indexed the windows wrong that would produce a retarded or advanced state.  A timing light will answer this and likely rule out the new flexplate.

 

I think you more likely have a MAP issue or a vacuum leak.  I would use brake clean (non-chlorinated) to look for vacuum leaks, and check the MAP output or swap a known good one.  But please put the timing light on it first, or at least at the same time.

[Dando]

34 minutes ago, DirtyComanche said:

 

The windows in the flexplate are what the crank position sensor reads, and that's the basis of how it determines when ignition and injection events are to occur.  Obviously ignition advance/retard is modified beyond that baseline depending on the output of other sensors, but those windows and the crank position sensor sets the base timing.  If those windows are screwed up the timing will likely be hunting, or way advanced or way retarded.  As I previously mentioned, the one my friend had refused to idle properly as the timing was going amuck at that point, but his issue was that the windows in the flexplate were the wrong size, if they had simply indexed the windows wrong that would produce a retarded or advanced state.  A timing light will answer this and likely rule out the new flexplate.

 

I think you more likely have a MAP issue or a vacuum leak.  I would use brake clean (non-chlorinated) to look for vacuum leaks, and check the MAP output or swap a known good one.  But please put the timing light on it first, or at least at the same time.

 

Thank you, that explanation of why the timing light will help was what I needed help with understanding. I've already swapped my map sensor with a known good one earlier today, with no response. Reached out to my local jeep club to see if someone has a timing light I can use. 

[carnuck]

It could be the tone ring was welded slightly off from where it should be. You may have to slot the crank sensor to get it closer to the correct timing.


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[Dando]

6 hours ago, carnuck said:

It could be the tone ring was welded slightly off from where it should be. You may have to slot the crank sensor to get it closer to the correct timing.


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This is exactly what it seems like. Can you explain what I would have to do to try to slot the cps? My truck hasn’t been driven in over two months now and it’s killing me 

[carnuck]

 
This is exactly what it seems like. Can you explain what I would have to do to try to slot the cps? My truck hasn’t been driven in over two months now and it’s killing me 

I would check the timing with a light first but there is a post here with pictures of a slotted sensor.


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[Dando]

44 minutes ago, carnuck said:

 

I would check the timing with a light first but there is a post here with pictures of a slotted sensor.


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Thanks I’ll search it out, I did get a timing light on it and it’s jumping all over the place 

[carnuck]

It should vary with RPMs. Even with the center of yours broken you should be able to tell where the tone ring sat. I can’t recall if the big slots were at CPS on TDC but the converter holes should let you see it at TDC #1 or #6 (same point) if it’s aligned or off a lot.
The RENIXPower group on yahoo has/had diagrams showing how it aligned.


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[Dando]

*UPDATE* 

 

as of today I have a running/driving Comanche again. Thanks to a member here, I got a stock flexplate shipped to me. Spent the day today removing the trans and putting in the flexplate. Started right up and runs great. Thanks everyone.