Hi everyone, first post here, and looking for some help. Here is the (long) story:

My dad has a 1999 Mazda B3000 (3.0 FFV) 4x4 which was running rough, so he asked me to take a look at it. I test drove it around the block and immediately felt that it was running down a cylinder because it was shaking and had very little power. Checked the #4 plug (easiest to get to) and it looked very good, so I then checked the DIS coil to see if all cylinders were firing by pulling the wire cap off slightly to see if there was spark. All were ok, exc cyl #2, so I changed the coil pack, and re checked the spark by pulling the caps off one at a time again, this time everything fired ok, so I congratulated myself on a job well done.

Not so fast, though. Not even a week later, same thing, actually worse this time around. I replace the plugs and wires, even though they all looked ok, except for the #2 wire, which was corroded and broke off at the plug when I removed it. (New plugs were Bosch super plus, which I have since read may not be the best choice for this type of ignition, wires were "prostart" 8mm.) I gapped the plugs to ~0.044 as the underhood sticker states. Again, same thing, the #2 cyl wire does not spark. I even switched the original coil back in, and same issue, no spark for cyl #2. The #2 plug was soaked in gas when removed, so it looks like everything else is working fine, and I'm all out of ideas.

I read on the tech section here that the DIS system fires two cyl at the same time, so #2 and #6 would fire at the same time and are on the same coil. I'm not really sure I understand this, as #6 is firing ok, and #2 not at all in this case. I have tried removing the plug from the cyl and grounding it on the intake manifold, and still no spark. I also tried removing the #6 wire, to see if this would make #2 fire, again nothing.

Sorry for the long description, but searching several forums has revealed nothing. I am hoping some ignition experts here can help me out. I can take pictures, video of this condition if it would help.

Thanks!

 

Welcome to FTE.

Cudo's on finding & using the Tech Info page.

Yes this engine uses a waste spark ignition system & I agree you may not have the best option for plugs & wires, as this system works the plugs & wires twice as hard as the old distribtor/single coil ignition, as the waste spark system fires the plugs on each rotation of the crankshaft & half of the plugs get a reverse polarity spark.

It fires once on the compresson/power stroke & again on the exhaust stroke(waste spark) & the drivers side bank of plugs gets the reverse polarity spark, so the plugs & wires have to be desgned to tolerate this double work load & reverse polarity spark, for them to last a long time.

If we don't use at least double platinum, or the new fine wire iridium enhanced center electrode, with platinum side wire plugs, the spark gap will prematurly erode & open up in 20-30K miles, or the plug wires insulation just won't stand up to the double work load & we'll have misfires, or driveability problems early on.

All that said, that covers extended service & this doesn't sound like it's your problem, from what you've posted.

It sounds to me like the new coilpack may have a problem.

Have you tried checking the end to end resistance of the suspect #6 plug wire, to make sure it's not open circuit, or if it's resistance has gone really high???? Plug wire resistance should be approx 1K ohm/inch of length, 30k ohms max, no matter the wire length.
Or have you tried swapping #6 wire out for a known good plug wire from the old set????

Have you done a secondary resistance check on the replacement coil pack????
As #2 & #6 plug share the same scondary coil, (one is connected to the end of the start winding, the other to the end of the finish finish winding, so you should have a secondary resistance reading from the #2 to #6 plug wire connection point at the coilpack & it should be 13-15k ohms.

Most autoparts stores around me can bench test the coilpack for output, or you could safely use your inductive timing light, to check for spark.

If you find the new coilpack is bad, be sure to have the replacement bench checked for output before leaving the store, or at least have them check the coilpacks primary & secondary resistance. The primary doesn't have a resistance spec, but should be less than say 2 ohms, maybe even less than 1 ohm.

The coilpack is known to crack on the bottom where it can't be seen, so maybe remove it & have a look see for cracks, or signs of electrical breakdown, carbon tracks, ect.

A whole bunch of thoughts for pondering, let us know what you find.

 

Hey pawpaw, Thanks a lot for your response.

I checked the resistance on the new #6 and #2 wires, and they are very close to the 1k Ohm/In that you suggested. The old wires are also very close to that (probably a bit less), unfortunately I can't know which was the #6 wire, and the #2 wire broke at the plug connector when I removed it.

I also checked the sec. resistance across the 2-6 coil, and it reads 13.65k on the old coil (currently installed) and 12.8 on the new coil which is now uninstalled. Primary resistance was 0 on both new and old coilpacks.

The original coilpack appears to be in pretty good shape, no cracks that I could see, the new one as well.

Thanks for your input.

 

OK, good feedback.

So now with the old coilpack installed, do you have spark on the #6 plug wire????

 

Yep, #6 is fine. Still nothing on #2 though.

 

Woooops, my bad, I got confused & thought we were having a problem with #6 & upon re-reading your initial post now have my mind squared away!!!! lol

Anyway, have you substituted a known good #2 wire???? Any one that is long enough & known good, will do for the test.

If you've tried that & you still don't have spark, check the spark plug center electrode for an intenal problem, to make sure it isn't shorted to the shell, or it's internal & external insulators, to make sure they aren't chipped, or cracked & messing with the spark.

Or, just swap in one of the old known good plugs into the #2 cyl & see what gives.

Seems to me, if the coilpack primary & secondary resistance checkout, you should have spark on #6.

About the only thing remaining is the plug wire & plug itself.

If the secondary winding were open to #2, you couldn't read the coils resistance.

If plug wire #2 resistance checks out, it isn't open circuit or high resistance.

If you swap out #2 plug for a known good one, that could eliminate a hidden problem in the new #2 plug.

So if you still have no spark on #2, seems to me that would leave us looking at an internal high voltage leakage/break down problem with #2 plugs part of the coil pack winding, so thats why I was suggesting a bench output test, or a test with an inductive type timing light on #2.