Help Me Diagnose My Miss

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I have seen the roll pin shear on a new MP distributor. See if the reluctor is not moving
 
AJ/FormS said:
Well the reluctor is pinned to the shaft, so that's doubtful.
Give the rotor a little twist and let it snap back on it's own. It does snap back right?All the way to it's parked position,right? Every time right? If not,find out why and fix it.
If it behaves properly, prove the TDC mark is in fact TDC using the piston stop method. Then
put the crank at TDC#1, on the compression stroke. Then back it up to 20degrees advanced. Next pop the cap. And the rotor. Then check the reluctor vanes. One of them should be more or less directly lined up with the metal spike on the pick up (called the pole-piece).If it isn't, make it so, by loosening the D and rotating it. But first, make sure the Vcan rod is properly installed, not jammed and that the Vcan is properly working; use a vacuum pump.Next,sight a line down from the firing tip of the rotor to the aluminum housing, and with a Sharpie mark that position on the housing where you will be able to see it with the cap back on. Put the cap/rotor back on.Make sure the rotor is properly located and holds it's position. Now; That Sharpie mark better be right under whatever tower sends spark to #1 cylinder.

But if it's not, Then the reluctor may be improperly installed. Pop the cap and rotor again. Look at the top of the reluctor. You should see two slots down by the driveshaft; one with the roll-pin stuck in it. Pop that reluctor up off there, and put it back on using the other groove. I use a couple of screwdrivers to do this, whatever works, they're rarely very tight. Ok now align a reluctor vane (Any one) again with the pole-piece on the pick-up, by rotating the D. Erase the old Sharpie mark, and make a new one. Replace the rotor and cap.Again, that sharpie mark should be right under a tower. If it is, make sure the #1 wire goes to that tower and relocate the rest accordingly. Fire it up and set the base timing. Lock the D down and prove it's locked down by attempting to rotate the housing, by pulling on the Vcan.
So if it didn't move, then the base timing should theoretically never move again, except the tiny bit it does when the timing chain stretches.
If it starts running funny again, the first thing you can do is check the rotor alignment to the Sharpie mark you made. If it goes off by itself, that is not normal and should never happen. The possibilities are; jumped timing chain, a slipping intermediate driveshaft, faulty mechanical advance system, faulty reluctor plate location,slipping rotor. Of these, the first two usually spell disaster for the engine. The last three are the most likely. The very last one is the easiest to check.

BTW, the rotor does not have to be exactly in the center of the tower. But it has to be less than 1/2 the distance to the next nearest CCW tower. And since the advance mechanism rotates the rotor clockwise, the rotor can only be slightly CW of the tower. Else the advance mechanism will drive the rotor to the next tower. If it gets to the halfway mark, and the coil has enough power, it will rather spark there. So you do have a fairly wide target window, maxed out at about 15/16 degrees; Maybe 10CCW and 5 or 6 CW.
Ok so have at her,lol.
Click to expand...

I'm going to pull the distributor tonight and dig a little deeper once I check the rotor phasing. I've checked TDC and it's spot on. A lot of those other suggestions I've already checked as well. Considering it was running perfectly and started acting up at a stop light suddenly, I'm sure it's something stupid. Maybe the roll pin for the reluctor wasn't punched down all the way or something. I'll post up what I find tonight. For now, it's running great again with timing at 24 initial and 36 total.
 
Verify regulator is not shot. I don’t know what that pump is rated at but maybe try bypassing the regulator. My brothers car had those exact symptoms. Just started running like crap all of a sudden and wouldn’t idle. After we completely disassembled the engine looking for the problem, we finally found the Holley regulator had **** the bed and was drowning the engine.
 
SSG_Karg said:
Verify regulator is not shot. I don’t know what that pump is rated at but maybe try bypassing the regulator. My brothers car had those exact symptoms. Just started running like crap all of a sudden and wouldn’t idle. After we completely disassembled the engine looking for the problem, we finally found the Holley regulator had **** the bed and was drowning the engine.
Click to expand...

I just rebuilt the regulator. I appreciate the input, but it's not a fuel problem. The timing was way off. It runs awesome now. I just have to figure out what caused the timing jump so significantly.
 
AJ/FormS said:
Well the reluctor is pinned to the shaft, so that's doubtful.
Give the rotor a little twist and let it snap back on it's own. It does snap back right?All the way to it's parked position,right? Every time right? If not,find out why and fix it.
If it behaves properly, prove the TDC mark is in fact TDC using the piston stop method. Then
put the crank at TDC#1, on the compression stroke. Then back it up to 20degrees advanced. Next pop the cap. And the rotor. Then check the reluctor vanes. One of them should be more or less directly lined up with the metal spike on the pick up (called the pole-piece).If it isn't, make it so, by loosening the D and rotating it. But first, make sure the Vcan rod is properly installed, not jammed and that the Vcan is properly working; use a vacuum pump.Next,sight a line down from the firing tip of the rotor to the aluminum housing, and with a Sharpie mark that position on the housing where you will be able to see it with the cap back on. Put the cap/rotor back on.Make sure the rotor is properly located and holds it's position. Now; That Sharpie mark better be right under whatever tower sends spark to #1 cylinder.

But if it's not, Then the reluctor may be improperly installed. Pop the cap and rotor again. Look at the top of the reluctor. You should see two slots down by the driveshaft; one with the roll-pin stuck in it. Pop that reluctor up off there, and put it back on using the other groove. I use a couple of screwdrivers to do this, whatever works, they're rarely very tight. Ok now align a reluctor vane (Any one) again with the pole-piece on the pick-up, by rotating the D. Erase the old Sharpie mark, and make a new one. Replace the rotor and cap.Again, that sharpie mark should be right under a tower. If it is, make sure the #1 wire goes to that tower and relocate the rest accordingly. Fire it up and set the base timing. Lock the D down and prove it's locked down by attempting to rotate the housing, by pulling on the Vcan.
So if it didn't move, then the base timing should theoretically never move again, except the tiny bit it does when the timing chain stretches.
If it starts running funny again, the first thing you can do is check the rotor alignment to the Sharpie mark you made. If it goes off by itself, that is not normal and should never happen. The possibilities are; jumped timing chain, a slipping intermediate driveshaft, faulty mechanical advance system, faulty reluctor plate location,slipping rotor. Of these, the first two usually spell disaster for the engine. The last three are the most likely. The very last one is the easiest to check.

BTW, the rotor does not have to be exactly in the center of the tower. But it has to be less than 1/2 the distance to the next nearest CCW tower. And since the advance mechanism rotates the rotor clockwise, the rotor can only be slightly CW of the tower. Else the advance mechanism will drive the rotor to the next tower. If it gets to the halfway mark, and the coil has enough power, it will rather spark there. So you do have a fairly wide target window, maxed out at about 15/16 degrees; Maybe 10CCW and 5 or 6 CW.
Ok so have at her,lol.
Click to expand...

This. This right here needs to be on video. Would be an awesome tutorial.
Im on a tractor forum, there are a few good reference videos. Like they say a picture is worth a thousand words.
 
I just have to figure out what caused the timing jump so significantly.
Click to expand...
Tchain jumped a tooth? EDIT A coil can perform good then act up when hot, same with cheap HEI modules. For sure post what it ends up being.
 
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AJ/FormS said:
19%! ho-lee!
Hey where did you get the tool to measure that, I want one. Can I afford it? Probably not,lol.
Click to expand...
Built into fuel system in newer impala,displayed on my nap-on solus scanner.
 
Rapid Robert said:
Tchain jumped a tooth? EDIT A coil can perform good then act up when hot, same with cheap HEI modules. For sure post what it ends up being.
Click to expand...

Is there an easy way to tell if the timing chain jumped a tooth? I would think that would completely change the characteristics of the engine by drastically changing the cam timing. How much is one tooth worth in terms of cam timing? It seems to be running as it did before this issue.

The coil definitely doesn't seem to be the issue. Checked a different HEI module too and it didn't change anything. I think it's probably in the distributor. Either way, I'll definitely post up what I find tomorrow. I appreciate the input.
 
Well, turns out the roll pin acting as a keyway on the reluctor/distributor shaft fell out. The reluctor wheel had shifted and the pin was just chillin at the bottom of the distributor. Thanks for the help guys. I'd never seen this one before.
 
Awesome. Makes perfect sense now, doesent it? Does to me. Another mystery solved.
 
mopowers said:
Well, turns out the roll pin acting as a keyway on the reluctor/distributor shaft fell out. The reluctor wheel had shifted and the pin was just chillin at the bottom of the distributor. Thanks for the help guys. I'd never seen this one before.
Click to expand...
Thanks for taking the time to let us know. That's the way we all learn. BTW, I lived in the Sacramento area (Rancho Cordova) twice while in the Air Force. Once as a Second Lieutenant for one year going to Nav School at Mather AFB, and once for 4 years as a Captain teaching at Nav School. BEAUTIFUL area.
 
harrisonm said:
Thanks for taking the time to let us know. That's the way we all learn. BTW, I lived in the Sacramento area (Rancho Cordova) twice while in the Air Force. Once as a Second Lieutenant for one year going to Nav School at Mather AFB, and once for 4 years as a Captain teaching at Nav School. BEAUTIFUL area.
Click to expand...

No problem. Thank you for your service! I appreciate it.
 
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