At worlds end: no spark: A little progress

[DocMel]

My original post was getting a little long, so I thought I would start again, this time with a little progress to share:  Hopefully the folks that have been following and helping so far will tag along as work continues

1.  While cranking the car, very strong spark at the coil lead.  So I know I have power while cranking at the MSD, and that it works, as well as the coil

2.  Next tip I got was to check for fire at each plug, using a known good spark plug cable and spark plug, and check every cylinder for fire

While I didn't have a new/extra HEI type spark cable to use, I disconnected each cable at the plugs, one at a time, inserted s new spark plug in the end, and checked for fire at that cylinder by grounding the plug on the head:  What I found was interesting

# 7 had good spark
# 5 none.
# 3 good spark
# 1 none

At this point I wanted to see if the cables were the prob, or maybe the distro/  So I switched the firing cables with the non firing cables, and got spark. 
(In other words the post on distributor is working, as long as I switched a non firing cable with a good cable

With me so far?

#2, #4, #7, no spark.   #8 a very weak spark.  (I did not try switching cables on this side)

So basically I only have 2 cylinders firing at this point.  I don't believe its the distro (new/w/new cap), and I don,t believe its the new plugs I installed

The only thing I haven't changed out since this prob started are the spark plug cables.  They are 8mm, but they are fairly old

So whats the consensus out there now?

[Strawdawg]

I guess you could ohm the cables, but you might as well replace them all with a new set

Not sure what other consensus you can come to.

[734406pk]

I think i am with you. It sounds like you have bad plug wires ( you probably know this already). How and why? Who knows? Do the plug wires have paint on them? Try some new wires. At least you know that your distributor amplifier and MSD 6A is working. The issue is between the distributor and the plugs (wires, Kv leakage to ground, high resistance etc). Troubleshooting is a process of elimination, congrats!

[Strawdawg]

734406pk always try to use logic and elimination in his troubleshooting advice.  I believe in doing the same thing.

Remember my comment from a prior post?

If you still have spark at the coil wire when you check it, I think I would pull a plug and a plug wire off another vehicle, remove one of your plug wires and replace it with the borrowed wire and plug and lay this plug on the valve cover so that it is grounded.  Then crank the engine over and watch the gap on the plug laying on the cover to see if it is sparking.

I was trying to help you drive the problem in a box.  I have found after way too many years that you have to be very methodical and narrow the problem down to a certain area and that means one has to never assume anything is good no matter how little information exists to the latter   

I was having a hard time trying to understand why there was spark at the coil wire and none in the plugs...that narrowed it down to either a shorted rotor, bad cap, or wires and/or plugs.

I hope you found it 

[734406pk]

734406pk always try to use logic and elimination in his troubleshooting advice.  I believe in doing the same thing.

Remember my comment from a prior post?

I was trying to help you drive the problem in a box.  I have found after way too many years that you have to be very methodical and narrow the problem down to a certain area and that means one has to never assume anything is good no matter how little information exists to the latter   

I was having a hard time trying to understand why there was spark at the coil wire and none in the plugs...that narrowed it down to either a shorted rotor, bad cap, or wires and/or plugs.

I hope you found it 

Thank you very much Strawdawg! You are a true professional and a great asset to this site!:thumbsup: I hope this issue has been resolved! (if not, post back)I treat these issues as if they were happening with my own car. This is what I do, and happy to do it.

[73_Cuda_4_Me]

When I worked at Oceana Dodge a long time ago, I experienced plug wires on customer cars that were purchased new from local shops which had the end contacts incorrectly crimped and the 'prong' wasn't hitting the conductor, and contacts that didn't slip fit into cap far enough to make contact with cap tower plug.

If you can, take a non-firing one and push dizzy boot of plug wire further up on wire, and try inserting the contact down into the cap... you should feel a definite engagement.

Ohm the wire with plug and cap attached, and read between plug center conductor and cap spark contact inside the cap - ensure you have proper resistance for length of plug wire.

[67vertman]

Your getting there Doc.  since you know that you are getting spark from one spark plug wire and spark plug, I would use that (good wire and spark plug) to test the other seven terminals on the distributor.  If you get spark from each terminal of the cap, then you know it is the spark plug wires. If you still only get spark from some terminals let us know which ones.

Do you think it is possible that the MSD switched from 8 cylinder mode to 4 cylinder mode?

[DocMel]

For the box to go from 8, 6, 4 cylinders, I would have to actually modify the small wires at the box.   But then again, I would have never have thought that almost all my spark plug cables would have gone south (If thats the case)

I will certianly check all wires with a good one before I get a new wire set.   Ill do that today and post results.    Ill also take my other, good  MSD box and check again, based on your input   It cant hurt........

[Chryco Psycho]

it could be a bad signal at the pick up coil just picking up certain vanes

[HP_Cuda]

As mentioned before, new plug wires will probably do the trick and are not that expensive a fix to go for.

[cudabob496]

I suspect the MSD box.
there's a small black cap with a screw in it, on the side.
I had to open that up and cut one wire, to get mine to work.

[734406pk]

I suspect the MSD box.
there's a small black cap with a screw in it, on the side.
I had to open that up and cut one wire, to get mine to work.

The MSD box should still be disconnected at this time and out of the picture for now. The questionable sparkplug wires are in the process of being replaced.

[DocMel]

Finally, spark at all 8 cylinders.   The end result is great, but makes no sense to me.  But also realizing that electronics can be really finicky at times, and can work one time, but not the next, with the same exact setup.........

Today I checked all cylinders with one good park plug cable and a good spark plug .  I removed all spark plug wires, and went around all cylinder distro post and tested one at a time.  Again, no spark at all but 2 cylinders

So again, I checked for spark at the coil lead.  What I saw, (and have been seeing), was a good spark, but it wasn't constant.  Spark at the coil lead should be a steady and rapid fire.  Instead it was in a somewhat inconsistent, consistent pattern  (if you can get what I mean here)

So once again, I took the msd box off my off roader and tried it on the cuda, and vice versa:  Great fire on my off roader with both boxes, the same inconsistent spark at the coil lead on the cuda w/both boxes. 

Same no fire on all but two cylinders on the cuda with both boxes

So I figured I would try one more thing:  Take the msd box completely out of the circuit.  I would use the MSD 2 coil, but wire the ready to run distro with no MSD box.  (I had done this once before a few days ago)

And yes, I got fire at all 8 cylinders......   So...

I ordered a new set of accel ceramic boot spark plug wires. (I run headres)

 I will take the new plugs out, clean them as I am sure there is raw gas on them, and regap back from .050 (as one would do with a MSD box) down to .035

I wont even pretend why I have a good solid spark at all 8 cylinders now. 

The MSD box on my cuda works fine on my off-roader.   Ill miss that fat MSD box spark I am used to on every other vehicle that I have run a MSD box on  (maybe 5-6 past vehicles) 

But at least Ill have an extra one for my off roader in case the one on it now goes south

Also, my thanks to all of the input rec'd.  The checks that were suggested helped me eliminate some things that might have been wrong

But I am still wondering, WTF.........   

[70chall440]

So, what you are saying is that on your Cuda the MSD box is causing inconsistent/unreliable spark but in your off road rig it works perfectly? If this is correct, then I would assume that the wiring to or from the MSD box has an issue (which I am sure you surmised). I am interested because I have a brand new MSD digital box in my Cuda but have yet to wire it up or start the car. I am also running a new MSD distributor (I like to keep like brands together when possible). I have a long way to go before I am firing anything up, but am trying to set myself up for success. I am running an after market wiring harness and wiring everything from scratch.

[734406pk]

Finally, spark at all 8 cylinders.   The end result is great, but makes no sense to me.  But also realizing that electronics can be really finicky at times, and can work one time, but not the next, with the same exact setup.........

Today I checked all cylinders with one good park plug cable and a good spark plug .  I removed all spark plug wires, and went around all cylinder distro post and tested one at a time.  Again, no spark at all but 2 cylinders

So again, I checked for spark at the coil lead.  What I saw, (and have been seeing), was a good spark, but it wasn't constant.  Spark at the coil lead should be a steady and rapid fire.  Instead it was in a somewhat inconsistent, consistent pattern  (if you can get what I mean here)

So once again, I took the msd box off my off roader and tried it on the cuda, and vice versa:  Great fire on my off roader with both boxes, the same inconsistent spark at the coil lead on the cuda w/both boxes. 

Same no fire on all but two cylinders on the cuda with both boxes

So I figured I would try one more thing:  Take the msd box completely out of the circuit.  I would use the MSD 2 coil, but wire the ready to run distro with no MSD box.  (I had done this once before a few days ago)

And yes, I got fire at all 8 cylinders......   So...

I ordered a new set of accel ceramic boot spark plug wires. (I run headres)

 I will take the new plugs out, clean them as I am sure there is raw gas on them, and regap back from .050 (as one would do with a MSD box) down to .035

I wont even pretend why I have a good solid spark at all 8 cylinders now. 

The MSD box on my cuda works fine on my off-roader.   Ill miss that fat MSD box spark I am used to on every other vehicle that I have run a MSD box on  (maybe 5-6 past vehicles) 

But at least Ill have an extra one for my off roader in case the one on it now goes south

Also, my thanks to all of the input rec'd.  The checks that were suggested helped me eliminate some things that might have been wrong

But I am still wondering, WTF.........   

I would have to suspect that the Summit RTR distributor (which is made to simply connect directly to the coil) is not completely compatible with the MSD 6201, or some low voltage issue that reduces the signal when you have both the MSD 6201 and Summit RTR connected all at once. I think you would be better off with a mag pick up type distributor not the RTR and wire it into the violet and green wires on the MSD 6201. I'm not seeing an advantage in amplifing and already amplified signal to the coil. Just more room for trouble IMHO.