MSefi.com read only forum (Jan.15,2018)

After the 25th time looking at my wiring I am still convinced it is correct. It is slightly different than the diagram above but I think I am still ok.

Old small block Ford firing order: 15426378
converted to EDIS speak:
ABCD
1532
6378

EDIS module post #8 goes to coil A which has plug wires 1/6
EDIS module post #9 goes to coil B which has plug wires 5/3
EDIS module post #11 goes to coil C which has plug wires 3/7
EDIS module post #12 gooes to coil D which has plug wires 2/8

The only "difference" is that in my arrangement my coil A is not the one with the thick part of the wiring plug it is the other coil. I do not think it matters since the coil I am calling A is wired to post #8 on the EDIS. I did this at the time because my salvage yard coils both have the same wiring colors unlike the diagram above. It could be when they pulled them they mixed them up.

I also checked for solid 12V at the EDIS. If the VR is wired backward I do not think it will start. That leaves the EDIS module itself which I just cannot imagine is faulty.

Ideas?

Thanks

ABCD
1532
6378

EDIS module post #8 goes to coil A which has plug wires 1/6
EDIS module post #9 goes to coil B which has plug wires 5/3
EDIS module post #11 goes to coil C which has plug wires 3/7
EDIS module post #12 gooes to coil D which has plug wires 2/8

Mark,

The above is correct except, two #3 cylinders is unlikely, even on a Ford!!

It looks like a simple typo but maybe you want to double check that #3 is not paired with #7...... Of course, #4 and #7 are complimentary cylinders on your sbf.

Your issue is certainly a strange one. Since you are not controlling fuel (ie. carb'd), have you tried to run the car without the MS connected at all? As I'm sure you know, the engine should start and run (in limp mode of course) even if your MS was off visiting your mother-in-law.

Ken

EDIT:

If the VR is wired backward I do not think it will start

I wouldn't be so sure about that. Recently I made a number of changes to my wasted spark setup (new wheel, sensor etc). I ran but it ran like crap...... Until I swapped the VR wires that is........

What is the true ignition advance figure you're seeing at idle - using your timing light? Does this changes when it stumbles?

Yes I did a typo..sorry for that.

At idle my timing is 10 degrees. If I just hold the timing light and watch it, the light goes out once in a while. I assume this is happening on other cylinders also. I did run it with the MS disconnected and had the same behavior.

I was really hoping someone would look at my log and sat "oh yeah its this" and maybe I had a software setting off but no luck.

Tonight I reversed the VR wires and it would not start. Switched them back still running poorly.

Any suggestions? I guess I need an EDIS module. I do not know what else to test.

Could these symptoms be caused by run out in the trigger wheel? Maybe it is wobbling and when I put it in drive it gets worse. How can I test that?

pcf_mark wrote:Could these symptoms be caused by run out in the trigger wheel? Maybe it is wobbling and when I put it in drive it gets worse. How can I test that?

That is certainly within the realm of possibility. How much run-out are we talking here?

Ken

pcf_mark wrote:Could these symptoms be caused by run out in the trigger wheel? Maybe it is wobbling and when I put it in drive it gets worse. How can I test that?

Check the gap at 3 points approx 1/3rd of a revolution apart.

I just went over my wiring a 4,345th time and still things all make sense. I also ran ground wire from battery to coils and to EDIS mounting bracket no changes.

I checked the gap at the VR and it is .47, .042, .060, .065" or a total run out of .023 for highest to lowest. When running in park I tried to push and pull the VR bracket and it does move around a little bit with some flex in the bracket. When running in park it is dead steady and it is mis firing. But while moving it around and tapping it the engine never changed (better or worse).

I pulled the plug wires off trying to locate a dead cylinder. Some do spark more aggressively than others and it does depend if the wire on the other cylinder is connected or not.

I am at the end of my rope with this. I hate to throw money at a problem replacing parts. but my logic is the coils are all good since I am getting spark to each cylinder. The VR is good since it is running at all. But how does an EDIS fail?

UPDATE! UPDATE!

I hope someone jumps on and reads this!

When I strobe each cylinder with the timing light I get some really interesting behavior that is very consistent. One wire on one cool fires very nicely and the timing light strobes very consistently and very fast. Switch to the other wire on the SAME coil and it is nearly dead. Random sparks or none for several seconds then a few then dead again. Every coil has the same behavior - one good cylinder one bad cylinder.

I do not know what to make of this. My next test is going to be to switch the wires from one post to another. If the formerly dead coil tower works I know it is in the coil. If not then it is in the wire or plug.

Other things I have tested: removed the capacitors from the coils, verified 12v at the coil, ran a second ground to coils and EDIS.

Anyone ever have this before?

Smacks of a bad coil IMO. A crack or carbon track in the offending coil tower causing the spark to arc to ground...... Just a thought, but I think you are on the right track!

I have certainly seen this in old school coils!

Ken

Be a simple job to swap coils and see if the fault moves with it. You say you've removed the caps - but those shouldn't make a difference as they are fitted to the battery feed - you've not by any chance fitted them to the EDIS side of the coil? (Their job is RFI suppression, so shouldn't have any effect on the spark)

Are you also using spark plugs with resistors? I'd also measure the resistance of the plug leads with a DVM - even although they are new. They will be so much per foot of length - something like 2000 ohms per foot or so, and a faulty one will be very much higher. I'd also measure the voltage at the coil positive to ground with the engine running to make sure it really is getting full battery voltage under load. An easier way would be to measure between coil positive and battery positive with the DVM, which will show the actual voltage drop in the circuit. Should be 0.5v maximum.

I disconnected the caps just as a check because I am running out of things to check. I have 14.2 v running at each coil.

I did a test on one coil tonight. This coil had one sparking fast and consistent and one that was sporadic in idle. When I move the wire that was sparking to the other post on the same coil that was previously not firing it starts to fire on that post. This makes me think the problem is in the new wires or new plugs. I have never seen that before. I did not gap the plugs when I installed them but surely they would fire a .050+ gap. They are supposed to be resistor plugs that is what I asked for. Now I need to check the number to be sure.

If it was carbon tracking would I see the spark finding another ground path?

When I move the wire that was sparking to the other post on the same coil that was previously not firing it starts to fire on that post.

Therein lies your clue! Based on your description, I would replace that wire.

If it was carbon tracking would I see the spark finding another ground path?

Absolutely! Hence, my response above.

Ken

I cleaned the coil towers while looking for any carbon tracing - nothing. I removed all the plugs - 4 completely fouled. I closed the gaps from .050 to .030 cleaned and re-installed. My situation is much improved. I can actually drive it around in the driveway. I still have this miss that randomly sneezes / pops through the carb. It only did it a few times compared to the disaster I had before.

Could it be incorrect plugs? They are supposed to be resistor type according to the AutoZone website but there is no R in the part number. The wires all checked out in the same range.

What is the make and part number of the plugs? I have the figure of 0.035" for EDIS plug gaps - but dunno where it came from. Works here ok. Again on the subject of resistor plugs, I read they had to be used so did. Luckily, a later version of my engine used EDIS, so I just got the ones specified for that.

The plugs are Motorcraft SP-420 / BSF42C.

I have also observed that the timing light picks up the spark in one direction for one cylinder and in the opposite direction for the other cylinder on the same coil. The arrow on the timing light pickup that say "to spark plug" needs to point to the coil for on of the pair and away from the coil for the other one. This may have had me thinking some of the pairs were dead. Then I think the spark plug gaps were too large and then they fouled out.

Now that I am running on all 8 cylinders but still randomly miss firing I am back to thinking my random miss fire is a bad component. Can I read the VR output to see if it consistent? I would like to eliminate that as a source of problems.

The arrow on the timing light pickup that say "to spark plug" needs to point to the coil for on of the pair and away from the coil for the other one.

That is the very nature of the EDIS design. It is normal so, nothing to worry about.

Ken

Took for a 1 mile test drive tonight. The miss fire is very present - sometimes worse sometimes almost hard to notice. I am back to thinking I have a bad component. But of course I have no idea which component. Would a log help diagnose? Can I back probe the signal going to the coils to see if they are getting a consistent signal? If the signal wavers EDIS or VR, if it is solid then the coils?

I really want this to go away so I can get my fuel side going!

Were all the fouled plugs on the same coil?