EDIS problems and supplies

So I’ve spent the last couple of days trying to “tune” the car with its new EDIS system. I have twin Strom’s. Couple of odd things…

Using a Colortune I get blue across all cylinders but I can’t seem to change that color no matter how much I adjust the jets??

The engine starts and runs ok but has a constant minor “shake” and now and then a pop from the exhaust, a misfire

I’ve carefully adjusted the floats to 11mm per the guide in the kit.

I started with the jets 3 full turns down form the bridge, per J Curto’s advice.

Tried different plugs

I now wondering if I have a bad set of coils, so, anyone in the US know where a replacement set can be obtained?

Any other suggestions on the aforementioned problem?

Have you fitted resistor plugs which are pretty much essential even with resistor wire? e.g. BPR5

Coil packs are pretty rugged and if they fail they do so in a big way so unlikely to be the cause of your problems.

Check the plug going into the EDIS unit and the one to the coil pack - the U shaped connectors may need to be carefully crimped together a bit to ensure a tight fit. Use a fine set of pliers or tweezers to squeeze the ends. Similar problems reported here: http://forum.etypeuk.com/viewtopic.php?p=32447#p32447

If all else fails post in the Megajolt support thread: http://forum.etypeuk.com/viewtopic.php?f=9&t=437


Just an idea but with the Colortune in each cylinder, one at a time, might you observe a change in the flame concurrent with the “miss”? If so you would be able to isolate further diagnostic to one lead? one carb? one U shaped connector? etc.

Not yet, I’m using the std Champion plugs, but will try them, thanks.

As an added piece of info, all cylinder pressures are good and within 10% or less of each other…150 - 160.

Can’t see the threads on the UK forum you indicated David. Have to be registered to see them and apparently I screwed up my registration so have to “wait until later” to try again…however long “later” is.

I have use the Colortune one cylinder at a time John, to check for mixture. Tough to be certain but I might have seen #1 miss a beat now and then but the shake and is permanent, regardless and I can’t really see much change in the flame color or regularity. Might be easier in a darker environment.

As David and yourself has suggested, I’ll check out all connectors.

Odd - there should no no time constraints. PM me your email address and username you want and I will set you up from this side.

Anyway - Resistor plugs are your first go to as they will only cost you about $12 for six. Next check those connectors or you may be stranded on the side of the road. The connectors should have silicone jelly sealant in them to prevent water ingress.


Les - I have set your membership of the UK Forum up and emailed you the username and password. Once you are logged in you will be able to view the links and a whole lot more besides. We hide a lot of content from anyone who is not logged in as we don’t want Google’s bots crawling over everything and broadcasting it to the world.



Les, may sound evident but better to ask: do you have the firing order in the correct sequence?
The coilpack has a sticker which is for V6 engine, while you need to connect for inline 6.
Here is a pic taken from Ray’s write-up illustrating the correct order:

I support David’s suggestion. It is a mystery I have not yet been able to find an explanation for.

I was running non-resistor plugs on the EDIS-8 system on my Jensen Interceptor (440), (believing that the Magnecor HT wires would “do the job”) and found that the car would cut out every now and then. Turned out it was the ignition module that overheated and the transistors shut themselves down to protect themselves.

Fitting resistor-ed plugs sorted the problem.

The type of spark plug is also said to be important. As understand it, the secondary wiring in a standard coil is connected to the spark plug through the distributor on the positive side and to ground on the negative side. The current goes through the electrode and by jumping the gap it returns to ground. In an EDIS system what would ordinarily be the positive and negative side of the secondary winding is now connected to the center electrode of two complementary plugs (eg 1 and 6 on an XK motor). When 1 fires on the compression stroke it can only complete a return connection to the other side of the coil by in turn firing through 6 which is at the same position on the exhaust stroke, but this spark is in the reverse direction - that is from the ground to the electrode. This is the so called “lost spark”. As a result the EDIS system needs only 3 coils as opposed to 6. (I’m way out of my expertise here but I suspect that the EDIS system works by alternating polarity on the complementary plugs depending on which is actually firing. I’d enjoy hearing from somebody who knows about this.) The point of all this is that the system needs plugs that are efficient in jumping the gap in both directions. That is the iridium plug.
I have this really grumpy engine in my '68 - big valves, ported, stroked, with cams that are a little too aggressive and it doesn’t want to idle below 1000 rpm. Unfortunately at that idle speed it will run on after switching off. Going to an EDIS system really helped, and going to iridium plugs from standard resistor plugs also really helped. It now idles (not really happily) at 700 and shuts off. The plugs are NGK BPR5EIX. Expensive but they last forever, which is a good excuse to buy them - right?

Have taken all advice and it hasn’t made much of a difference, however, my car came to me with triple webers, and an aftermarket electronic pump. I did fit a fuel pressure regulator in the Weber system but of course the car is now with Stroms and without said regulator…so I’m now wondering if the heart of the problem might well be too much pressure from the existing pump…hence my questions about which pump to get.

Anyway, if this turns out to be the case I’ll feed the info back so the lucky few who have Stroms still fitted, can benefit from the experience!

That is absolutely not true! BOTH plugs have their center electrodes connected to the same coil. BOTH plugs have their ground electrodes connected to… wait for it… GROUND. After all, they’re both screwed into the same head. What you describe would require the current to flow from from the coil to the center electrode of the #1 plug, jump the gap to the ground electrode, then to the head at the #1 plug body, across the head to the #6 plug body, to the #6 ground electrode, jump the gap to the center electrode, and back to the coil. That path violates several basic laws of physics and electricity. Besides which, what you describe would lead to constant back-firing through the carbs, as all the plugs would be firing when their intake valves are open.

In reality, when #1 reaches TDC on the compression stroke, the #1 plug will fire, the #6 plug will NOT fire. When #6 reaches TDC on the compression stroke, the #6 plug will fire, the #1 plug will NOT fire. For both current flow will ALWAYS be from the center electrode to ground. There is no electrical trickery to which plug fires, and the coil neither knows nor cares which cylinder fires - the plug that is under compression fires, because it is easier for the spark to jump the gap in that cylinder due to the dense, compressed fuel/air mixture.

Ray L.

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You are absolutely CORRECT Terry.

Ray, respectfully, you are wrong on this matter. Please consult an electronic engineer on this matter to verify independently.

An EDIS coil DOES NOT FIRE TO GROUND. It fires from one HT terminal to another. This spark current does pass THROUGH the head though from the body of one spark plug to another.

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He was talking about a wasted spark set up. A typical 6 cylinder coil pack only has 3 coils with each coil having two outputs. So if 1 and 6 are on the same coil then both spark simultaneously but only one has a mixture to ignite.
Also…there are quite a few parameters that affect the discharge voltage between two conductors…but I think that at the dimensions and pressures encountered on an internal combustion engine the higher the compression ratio the HIGHER the plug voltage required…and the system designers put PLENTY of energy into their coil packs to jump both the spark plug gaps at full compression pressure…so both plugs have a fat blue spark that will rattle your teeth loose if you can’t let go…!!!

You might want to recheck your float level spec. I use 16.5mm which is pretty universal for most Zenith Strombergs.

So my question remains - does it matter for spark efficiencies whether the spark emits from the center electrode or the ground electrode? Maybe not? Interestingly a friend of mine here, who was service rep from Ford (now retired) says there is no polarity shift in the coils to ensure firing from the central electrode on the compression stroke. He has a later version of the Thunderbird with a V8 engine, with a factory installed EDIS system. He says that Ford specs for the car have different spark plugs for the four complimentary cylinders. Curiosity killed the cat - I’ve got an abiding interest in knowing how things work - ok an obsession, so the answer is not life or death, maybe. I do know my car runs better on Iridium plugs, which are said to fire backwards better than any others.

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Terry, I can not say with absolute certainly if it matters or not. What I can say is that I’ve installed EDIS coil packs on numerous engines, my own V12 XJS, a Jag V12 Cobra replica I built, and my own EFI-converted E-type V12, several Rover V8s, and most recently, my own Jensen Interceptor 440 cubic inch V8.

If it matters, it matters so little that its of no consequence.

Interesting questions on the intricacies of the wasted spark set up.
I suspect there will be a difference in discharge voltages depending on the direction of electron flow. Lightning rods are a preferred path for discharge to earth because of their sharp end so there is a phenomenon relying on concentration of electrons…ie shape…which is at play. The Engineers would apply so much voltage to the circuit to easily discharge over the gap…in either direction…so the system would work if someone didn’t pay attention to the subtlety of different spark plugs.
I think the current flow innthensecondary circuit will always be in the same direction. When the primary coil is switched off the magnetic field collapses. The secondary coil circuit reacts to maintain the strength of the magnetic field by inducing a current flow. This will always be in the same direction because the primary coil current flow is DC and always in the same direction.

Thanks Matt - I had assumed that after the first spark there would be a voltage drop of some kind before the second, and that the second would therefore be a pale shadow of the first. If the spark occurs on the exhaust stroke it doesn’t matter of course - there is no compression in the cylinder, and jumping the gap might be easier - though the composition of the “air” in the cylinder on exhaust would be different from on compression and may ionize differently.

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