Ground Issue? Intermittent Spark

[Tim Kay]

In my Tornado with only about a two mile warning the motor started missing at the plugs progressively worse but giving me enough time to find a parking lot, at which point I could only get short burst of ignition when trying to fire the motor. First thing I checked was fuel & fuel pressure, both were fine so I towed her home.

Back at the shop I set out to diagnose an ignition problem:
(1) MSD 6AL tested fine (white wire to ground and coil wire throws an arc every time).
(2) Installed a new MSD Blaster Coil (and woo baby, it got me good on one of the MSD 6AL ground test!!)
(3) Grounded a spare plug to any given plug wire and spark is intermittent (while trying to start the motor) if at all. Spark is never consistent (ergo short burst of ignition).
(4) Tried a different test at the coil wire, this time stuck a used spark plug in the coil wire to ground and it sparks intermittent if at all (similar as the plug wire test except when it sparks it's rapid)
(5) Dual Sync Pro Billet Dizzy seems to be ok, circuit board lights are operating correctly.
(6) I've repeated all the test three times, in different sequence, same results.


Is it likely I have some kind of ground issue with the results of the above mentioned test? I'm kinda focused on why the coil wire is not a consistent rapid spark. I wonder if that's even a valid test (#4 above) since the MSD Troubleshoot instructions don't suggest that procedure. Am I damaging something by doing that?

Or do I need to look at the dizzy as the culprit here? I'm not sure if I can isolate the MSD & coil from the dizzy like I am trying to do.

 

[Jac Mac]

Before I start thinking too hard this early in 2014, have you checked rotor to cap contact at the center contact & or any crud buildup in the cap...

 

[Ian Anderson]

Mismatch parts on dizzy drive and cammeaning one has worn away and dizzy not now meshing correctly

I hope not!
Ian

 

[Tim Kay]

Before I start thinking too hard this early in 2014, have you checked rotor to cap contact at the center contact & or any crud buildup in the cap...

That's the way to approach the new year Jac Mac, "slow and easy" :thumbsup:
I did remove and inspect both cap & rotor real good, there is no wear to speak of (dizzy has only 2-3k mi logged). The only thing that appear odd to me was the gap between cap and rotor contact seems large, approx 1/8" (3mm). Is that normal?

Mismatch parts on dizzy drive and cammeaning one has worn away and dizzy not now meshing correctly

I hope not!
Ian

I have a real aversion to removing the dizzy but I'm afraid your correct Ian and I'll be taking it out for inspection. Another reason I fear faulting the dizzy is this is the third go-round with Accel Pro Billet in relatively short order at $300+usd, the last one ironically expired, almost to the day, one year ago.

 

[Howard Jones]

I wouldn't take the distributor out until I had replaced the cap and rotor with known good ones. Even if you need to buy a second set and that's not it you will have a good set from now on.

When you have the cap/rotor off check out the electronic sensor in the distributor. Is it loose, are the wires loose, does it appear to have rubbed on the little gear (stator) that is used for a timing pulse along with the sensor, is the gear firmly positioned on the shaft?

Any of these will get you what you have. I will say you have me worried about the third bad distributor. What was wrong with the last one? Something isn't right in your part selection?

If you are going thru cam/dis gears that fast then you need to do some research on cam/dis gear comparability. We all hope that's not it.

We could use some more info on your motor. Hyd roller? solid lifter? Cam type?

 

[Jac Mac]

Tim, on 26 January, 2010 you started a thread '-Engine wont start-' , just to save time have you rechecked on the cause of that problem to make sure history is not repeating itself?

 

[Dimi Terleckyj]

Tim

Your problem sounds very much like one I had some years ago with a Chevy 350 running a Mallory Dual point electronic distributor.

The electronic module in the distributor had packed it in and it would run then it would shut down then after a period it would run then it would shut down.
Then it wouldn't start, then it would.

If you can swap out the distributor module before going to any major dismantleing that would be my first starting point.

Dimi

 

[Tim Kay]

^ Dimi, good suggestion. The route I'm taking.

Howard, cap & rotor are not suspect (although a good suggestion) but inspection of the dizzy revealed rubbing on the sensors as you described. The rest of the electronics are secure and in good shape. Before I removed the dizzy I connected to the ECU to get a "sync" reading while cranking the motor which displayed "off", should be "on".

Tim, on 26 January, 2010 you started a thread '-Engine wont start-' , just to save time have you rechecked on the cause of that problem to make sure history is not repeating itself?

Jac Mac, your memory is astounding, I am doing the same diagnostics and quickly coming to the same conclusion that the dizzy is kaput. Certainly raises the question as Howard notes, what is causing these reaccurances.

Just got back from a speed shop and the owner there had some valuable experience regarding the same model Accel distributor I'm using. From the discussion we had he discovered this particular model, abeit a very good dizzy, is sensitive to spikes and needs inline filters to protect them. Ordered the new dizzy and when it gets in he will set me up with the necessary accessories.

Won't know anything further for another 10 days at which point I'll update this thread.

 

[Jim Cowden]

Tim

It may just be a poor product, If the dist has a module built in you can get issues with resistances ect between coils and modules they are generally matched.
This can cause modules to overheat and die prematurely.
Does MSD make a dist.
You should be able to test the output from the dist with a frequency meter(in most digital volt meters) if you don't have a scope.
Connect to the wire that sends the signal from dist to msd, if it changes dramatically when you loose spark when cranking I would be thinking dist as well.

Jim

 

[Robert May Eng.]

Are these msd ignition systems even necessary? Just about every hipo and stock engine in the world manages on standard ignition components quite well and are knocking out the best part of double the hp per cube while also revving a lot higher in standard road trim.I can see the advantage in a drag car when you are trying to drown the engine in fuel/nos but fail to understand the need on normal engines. I may be missing something here but what discernible advantage is there in the MSD over the stock components of an electronic ignition in a road car??? I have junked so many of these over the years that have proven problematic, it may well be down to my misunderstanding of the system.

Bob

 

[Jac Mac]

In Tims case he only has the MSD 6AL box & coil and if history has repeated itself it would appear that there is a compatibility problem with either the Accel distributor or possibly some of the other electronic goodies in use.
Personally dealing purely with Factory Ford electronic distributor the addition of the MSD6AL to that setup has always worked for me with the advantage of the easily available large dia cap/rotor/adapter. The centrifugal weight system in the Ford dizzy is robust & easy to change springs /advance curve on once you have done it a couple of times ( admittedly not as easy as an MSD with everything up under the rotor ).
Most of the 'bad press' for the Fords dizzy is a result of people using a dizzy that already has a couple of thousand miles on the clock.... funny part is I have yet to see a MSD or any other aftermart ignition setup last anywhere near that mileage.