Center Coil Left Tower Won't Fire

[Michael Savage]

1995 Monte Carlo 3100, I've replaced the module and replaced the Center Coils Left Tower Won't fire, same thing with 4 different coils and a brand new one, and I'm just stumped.

 

 

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[Galaxie500XL]

I'd suspect a wiring issue to/from the ECM and ICM.  Most likely, there's either a break or a short in one of the wires, considering you've already replaced the ICM, and the coil.

 

I found this on the internet...

 

Don’t forget, too, that ordinary secondary ignition problems can also cause misfires with DIS the same as a conventional ignition system. A bad spark plug wire or a worn or fouled spark plug will act just like a weak or bad DIS coil. So anytime you find an ignition problem that is isolated to a single cylinder, remove and inspect the spark plug and plug wire to rule out those possibilities.

 

Keep in mind, since the coil fires two cylinders, either could be a potential problem.  I'd pull the plugs for both, see what they look like.

[mfewtrail]

Are you testing for spark directly off the coil or through your spark plug wires? Go directly to the coil if you have not.

[Michael Savage]

Been checking the coil with the wire off either of the towers on it. Left one isn't firing and the Right one is, following the left coil the plug shows its been missing, right one looks fine. So far I'm stumped but I'll look over the wires to the ICM when I get the chance and see if any have gotten melted on anything appreciate it alot guys. First problem in a while and it had to be a weird one.

 

 

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[19Cutlass94]

Test the module to. New ones have been known to be bad too.

[Michael Savage]

Swapped out to one on a friend's car, same problem And mines working fine on his, gotta be somewhere else.

 

 

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[55trucker]

Which cylinder is not firing?......I'm assuming that #6 is misfiring..

 

if you've come this far and no replacement item has solved the issue then you've a problem upstream of the ICM..

 

seeing as all of the other cylinders are firing.......I get the impression that it's not a conductor problem at the ICM, none of the wires that feed to the ICM are individual coil specific, the crank trigger & cam sensor decide which cylinder is going to fire.

 

Seeing as you're OBD1.5 the ignition is sequential, try pulling the cam sensor and peak down into it's hole to see there is anything out of the ordinary with the reluctor, also check the crank trigger reluctor as well for a problem..

 

I can't think of anything else if all of the conductors are fine, a sensor reluctor may be bad.The PCM doesn't decide which cylinder fires, it just gets information from the crank & cam triggers courtesy of each ones reluctor wheel.

[Michael Savage]

Cylinder 3, it's the only one not firing(this is the firing order my car uses) never has matched the book. But yeah 3 is the only one out of the 6 not sparking and none of the others are weak, didn't see a problem with the wires tonight. Now the reluctors I have no idea about I'll get my dad to see if he can check on them. Appreciate the help again this has just been agrivating lol

 

 

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[Imp558]

Could it be that one tower is negative polarity. Those coils should only have positive secondary on 1 side like the 3800 unless they are radically different but look the same. You should have 2 dead cylinders.

[RobertISaar]

same coilpacks as a 3800(ICM itself is a bit different). I did investigate this a while ago to see what the polarization looked like.... I want to say the center coil was reversed compared to the outer two, but I don't know if that's relevant here. i'll see if I can dig around for that info.

 

I've had half of a coil fail before, but that's apparently been swapped around a few times. with one side of the coil disabled, it can still fire the other plug(according to both the service manual and some of my own real-world testing), but I want to say it's a weaker spark.

[RobertISaar]

here we go, I guess I made this 7/13/2014:

 

 

I guess it's the 2/5 pair that's reversed compared to the other two. red numbers indicate which way to wire the cylinders to cause more wear on the front bank of cylinders(easier diagnostics) when using plugs that have precious metal only on the center electrode instead of both.

Edited January 29, 2016 by RobertISaar

[55trucker]

the Center Coils Left Tower Won't fire,

 

 

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Let's clarify this......the *left* tower isn't firing?

 

that should be #6.......

[Imp558]

I'm still very confused on this, my understanding is that when the coil fires it travels through one spark plug into the head through the block, up the other head and then jumps the gap on the other spark plug in opposite polarity and returns to the other tower on the coil. so I guess I'm having trouble rationalizing how you can have a spark on one side of the coil and not the other. it seems the best way to do this test would be with the system all hooked up and an inductive timing light to verify that there is a spark traveling through the wire on both sides. it shouldn't be something you can measure off of the negative tower.

Edited January 29, 2016 by Imp558

[RobertISaar]

center paragraph. I've experienced that exact scenario with a half-dead coil.

 

[Michael Savage]

Yeah my coils when they've gone bad it's usually one side of them that stops sparking, but currently no matter what coil goes on the center from the front of the car the left center coil on mine Cylinder #3 isn't firing #6 the right center side of the coil is still firing. So far, if I swap a coil onto the center it doesn't change anything but the coil will work just fine on the left or the right just not the center and the coil swapped onto the center starts doing the same thing. So pretty much it's gotta be the CPSensor at this point I'm hoping lol

 

 

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[55trucker]

the schematic for the ign wires is correct (mine runs fine & I'm sure anyone else's does as well), you've got your #3 & #6 backwards.

 

since the coils *dual-spark*....... the cylinder that fires primarily fires pos to neg while it's counterpart fires neg to pos. The cyl that is on the exh overlap receives only a portion of the voltage that the primary cylinder receives to fire the plug. If you've got the cylinders backwards then BOTH cylinders will receive a low voltage as the coil is firing both on the exh overlap, reverse your high tension wires on the towers.

[RobertISaar]

as long as the wires are on the correct cylinder pair, it doesn't matter which cylinder it goes to. the spark(and electrode erosion) will occur in one direction with the wires on one way and it will just reverse itself when used in the other orientation. a plug that fires on the exhaust cycle "uses" less voltage because there is less resistance to arc formation, but that won't matter for the next ignition event that the cylinder pair experiences, since the roles get reversed.

[Schurkey]

when the coil fires it travels through one spark plug into the head through the block, up the other head and then jumps the gap on the other spark plug in opposite polarity and returns to the other tower on the coil. so I guess I'm having trouble rationalizing how you can have a spark on one side of the coil and not the other. it seems the best way to do this test would be with the system all hooked up and an inductive timing light to verify that there is a spark traveling through the wire on both sides. it shouldn't be something you can measure off of the negative tower.

Correct.  The spark does not "split" between the cylinders.  ONE current pulse fires TWO spark plugs--one of them in reverse polarity.

 

C'mon guys.  His coil works great on another vehicle.  Other coils don't work properly on his vehicle.  Unlikely to be a coil problem.  One cylinder of the pair runs.  The module only controls power and ground for the coil primary winding--so since one cylinder gets spark, it can't be a module problem unless the module is only powering the coil weakly.

 

I'd like to hear how he's testing the coil for proper spark.  This has not been properly explained.

 

 

First Guess:  Dead plug wire.

[55trucker]

 

I'd like to hear how he's testing the coil for proper spark. 

 

First Guess:  Dead plug wire.

That's what I thought as well, until he stated he has tested the coil with the plug wire *off* the tower......

 

have to take him at face value......

 

my thought.....bad reluctor that fires #6 not #3 (he has his plug wires connected in reverse.......set this straight then carry on) 

 

 

               * In a Wasted Spark ignition systems there are two spark plugs connected to the ends of one coil . Both spark plugs will therefore fire simultaneously. The one spark plug will be fired in the compression stroke of the first cylinder a- (power), and the other in the exhaust stroke of the opposed cylinder b - ( wasted ). When the time comes for cylinder “B†to fire in compression the “A†cylinder will fire in the exhaust stroke. Since both spark plugs are fired at the same time from the ends of only one coil they have opposed current flow. That is the spark “flows†from the center to the outside electrode in the one spark plug and from the outside electrode to the center in the second spark plugs. This can be seen with an oscilloscope very clearly as the “exhaust sparks†have much lower voltage flowing as there is no need for high energy to bridge the spark plug gap. i.e. no compression. They are of opposite (negative) direction to the “power sparks†(positive).    

 

What he could use is a spark tester.....

 

  https://i.ytimg.com/vi/PeGXQ0OTkvA/maxresdefault.jpg

[Imp558]

Here's what makes sense:

1) You won't ever find a spark on the negative post with a spark plug laying on a ground point like a typical ignition system.

2) If you have EVIDENCE of bad spark when looking at the plug or into the cylinder it must be a bad plug or a mechanical failure in that cylinder allowing moisture or bad compression.

 

If it were a bad ICM 2 cylinders should not be firing, same with a bad coil. Bad CPS or CMS would be other symptoms but not this.

 

Check for spark with something inductive, if you don't have an inductive pickup timing light or similar find your stupidest friend and talk him into grabbing that wire with wet hands... he'll let you know if there's spark.

Edited February 2, 2016 by Imp558

[Michael Savage]

Found a burnt wire behind the engine, fixed it and had O'Reilly replace the new coil and now it's working. Thanks guys!

 

 

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