Two of the plugs on the coil pack are bad ?

[Patriq]

I'm having trouble getting the engine to run properly after just having installed the whole system. At first I thought it just was the table that was all wrong.

Then I decided to look to see if I had sparks properly and evenly. When I installed the system I only had the timinglight on the first cylinder to check the timing.

Now I hooked up the timing light to all cylinders. It's a four cylinder engine. I then realize that cylinder 4 only gets sparks at odd intervals. And that cylinder 2 has no spark at all. My first recation is that maybe the leads are bad. So instead of trying with the extra set I have - I switch to put cylinder 4 lead on cylinder 1 coil outlet and vice versa. To my surprise cylinder 4 no runs perfectly and cylinder 1 has the same problems as cylinder 4 had previously.

Hm... maybe the same test would work for cylinder 2 & 3? And, yes it does. When I switch, cylinder 2 runs perfectly, and cylinder 3 siezes to fire.

This has me buffled. I thought that there were only two coils in the coilpack, and that it fired twice on a complete cyclus and sent the spark to two outlets. Can the outlets really be that damaged ? The coilpack was used when I bought it. I suppose that the trigger signal that comes from the EDIS module couldn't do that kind of damage to the coilpack that it causes this type of fault ?

Any one heard of this, or should I be looking for the fault elsewhere ?

And oh - yes, there are in the faulty outlets on the coil one spot in each that is dark. Looks almost like a burnt spot the size of a needle top - just where the bottom surface of the contact area meets the cylindrical surface. Other than that they look shiny as new - as do the other two, but without the black spot.

[david jenkins]

Don't trust a timing light to give sensible results! The wasted-spark coilpack sends a high-voltage puls down 2 leads simultaneously - one is a positive pulse, and the other is negative. One will trigger the light, and the other won't.

Been there, done that...

[Patriq]

Don't trust a timing light to give sensible results! The wasted-spark coilpack sends a high-voltage puls down 2 leads simultaneously - one is a positive pulse, and the other is negative. One will trigger the light, and the other won't.

Been there, done that...

Ok, but even so - how come I get the same result from only one of the outlets - regardless of if I'm measuring on cyl 1 or cyl 4 ?
The engine block can only be ground - it can't send a +Ve current, can it ? That would mean that the pulse the ignites is positive regardless.
And I would expect to see an even "stroboscopic" blink on each cyl?

There is a significant difference between outlet 1 and outlet 4 on the coilpack. 1 has a even stroboscopic rythm. 4 is sporadic. Shouldn't I see the same on both if both 4th and 1st has both negative and positive pulses ? And if 4th gets the negative pulses and 1st gets the positive pulses, then why do I anyway see some of the pulses on 4th, but not all ?

And, I can't really understand how one cyl would get a negative pulse - do you mean that the coil then earthens a postivie pulse coming from the block ? How is the positive pulse then induced through the block ?

Same with 2nd and 3rd. Why do I first get perfect pulses on 3rd and none on 2nd - and then the opposite if I switch the cables on the coilpack? Do you mean that there still is a pulse coming through outlet 2, but only that it is negative?
And how can it be negative ?

It's this difference between the coil on 1st&4th and 2nd&3rd that I neither can get to make sense. Why do I get sporadic/perfect signal on one pair, and none/perfect on the other pair. Shouldn't these two pairs display the same pattern then ?

[david jenkins]

The voltage ends up a huge amount more negative on one terminal, and a huge amount more positive on the other, relative to the chassis. I can't explain why you (and I) got intermittent flashes on one lead, and strong flashes on the other - it happened that way for me too. I can only suggest that the clip-on sensor was getting a strong signal on 1 pair of leads, but only just enough signal occasionally on the others.

In my case the engine was running quite nicely, but I decided to check the timing anyway - and panicked because I could only get an intermittent flash on lead 1. I went through the same process as you, seeing 2 leads good, 2 leads bad, but in the end I decided that I was chasing shadows as the engine was fine!

One test would be to identify a lead that's giving a poor signal, turn the sensor over (if it has an arrow on the sensor to indicate the way to connect it relative to the plug, turn it so the arrow's pointing the other way) and see how it behaves then.

Of course, I could be talking a load of irrelevant rubbish, but that's how it worked out for me!

Have fun,
David

[Patriq]

The voltage ends up a huge amount more negative on one terminal, and a huge amount more positive on the other, relative to the chassis. I can't explain why you (and I) got intermittent flashes on one lead, and strong flashes on the other - it happened that way for me too. I can only suggest that the clip-on sensor was getting a strong signal on 1 pair of leads, but only just enough signal occasionally on the others.

In my case the engine was running quite nicely, but I decided to check the timing anyway - and panicked because I could only get an intermittent flash on lead 1. I went through the same process as you, seeing 2 leads good, 2 leads bad, but in the end I decided that I was chasing shadows as the engine was fine!

One test would be to identify a lead that's giving a poor signal, turn the sensor over (if it has an arrow on the sensor to indicate the way to connect it relative to the plug, turn it so the arrow's pointing the other way) and see how it behaves then.

Of course, I could be talking a load of irrelevant rubbish, but that's how it worked out for me!

Have fun,
David

I think you are just right !

I just got back in again. I simply took of one plug at the time - connected it to a lead and looked for spark between plug and engine. And there was steady spark on all 4. Off course only at cranking - but still. So that rules out the coil-pack I think. And you seem to be just right !


I'll have to try to inverse the clip with my timing light on the lead tomorrow to see if you're asumption was right on negative and positive end as well.

This leaves me with the conclusion that my carbs are giving way to much fuel. I suspected it long before my previous ignition system failed and I started on MJLJ. I borrowed an ignition system for a while and had similar problems - but I then thought that my first ignition system was so bad it was making the car run porely (before failing completely), and that the borrowed system was set for an other car - and that made also the engine run porely.

I have an appointment with running the car in a bench to set the carbs - I just promised to sort ignition first before coming to him.

My plugs get sooty and black almost immediately. A sign that it is running to rich ?

[david jenkins]

My plugs get sooty and black almost immediately. A sign that it is running to rich ?

Absolutely! You should have a nice light brown colour if everything's about right (apart from when the cold-start is on).

Apart from the mixture, are you sure that your cold-start/choke mechanism is off?

David

[Patriq]

My plugs get sooty and black almost immediately. A sign that it is running to rich ?

Absolutely! You should have a nice light brown colour if everything's about right (apart from when the cold-start is on).

Apart from the mixture, are you sure that your cold-start/choke mechanism is off?

David

Yes, certain ! They are disconnected, and that was confirmed when I had them apart before installing MJLJ - changed all gaskets, bad jets etc

But since you mention it - it's a good idea to check again !
The stiff wire/rod that connects the two double webers and the coldstart wire that you pull, are not connected to the operating lever(s) for coldstart/choke on the carburettors.

As mentioned, the car has running poorly since just after I bought it. But many factors made me not suspect that it was running rich.