GM OBD1 and no O2 codes?

Only one plug at a time will fire then. I gotta agree with scott

Ok... If each coil sends two sparks at once and one spark is 'wasted', then why can't I make a new connection to the post to replace the one that failed?

I would be 'basically' putting a T fitting on #6 plug wire to fire #3 on the 'waste' spark. Actually I think I will jumper the plug wire ends at the coil under the boots with a spare chunk of plug wire trimmed at the ends. If it doesn't backfire or shoot sparks all over creation, then #3 should get the spark on it's compression stroke right?

Other than that I will just unplug that injector and drive easy. It 'did' make it down here the 250 km for our supply run running on 5 cylinders.... I can find a coil at my destination tomorrow or sometime in the next few weeks when I need the car again.

Mike

Well folks I know for sure this engine runs just fine with the coil post for #6 cylinder going to the #3 spark plug because it was that way when I got it. If anyone remembers, my firing order was seriously messed up but it ran nice. The previous owner had fun with the waste spark firing order....

Sooo... I hotwired an old plug wire to the post under the boot for #6 and just plugged it's end into the clip under the boot for the #3 plug and away it runs. The miss is gone and my timing light show fire on both 3 and 6 no problem.

Thanks all for the ideas, later...

Mike

I didn't know if it would actually work like that or not... I'd still fix it right ASAP

nate

It will be OK BUT I would replace that coil pack ASAP. The extra load of the second plug won't do it any good. The coil packs are basically two coils wound with a common ground and two taps. What has happened is one side has opened and caused the coil to fail.

The coil packs have no secondary ground. They fire in a loop thru both plugs and ground. One plug fires negative and the other positive. One of Mikes 3/6 coil towers must be grounded though -- through the icm. Not a pretty thought.

Our vacation got cut short/delayed, the place we were staying at had the main building totally closed for a serious environmental mold clean up with a dry ice blast job. Total zuit suit and respirator territory. The washroom was 'supposed' to be OK, but mold got found there too so the whole place is down for a week. Oh well, next week...

Well, it did 'kinda' work. It ran OK at low speeds but started missing worse at speed under load so I stopped and just ran #6 cylinder normal with the injector to #3 unplugged. It ran best that way.

I think the spark might have been leaking out under load, but it is moot now, we got a new coil for the drive back and it purrs again with 32 mpg.

I do not understand the GM waste spark system well.

When I got this car, the plug wires were seriously mix up on the coils, yet it ran beautifully and passed emissions with low numbers.

I did put new wires on and put them in the right order. It still runs sweet.

If the coils alternated the positive and negative power to make a block ground path for each spark, shouldn't one way run best?

Just curious because it might have even gotten a couple mpg 'better' when the wires were reversed? Or does it just not matter and only one power pulse comes through the harness to each coil so one cylinder fires a 'positive' spark and the other a 'negative' direction spark.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

Mike- The coils fire from tower to tower. The primary and secondary are insulated from each other and ground. On the 3/6 coil you could put either tower to 3 or 6. The only time it makes a difference is when the oem's use platinum plugs with only the electrode or ground having platinum and not both. The coils don't alternate firing. They always fire the same way. Because they fire in a loop, from one coil tower - thru the plug wire - thru the plug - thru the head - thru the other plug

- thru the other coil wire - and back to the coil to the other tower, one plug fires from the electrode to ground and the other plug fires from ground to electrode. The icm and coil never know which plug is firing a compressed charge and which is firing waste. Of course both plugs fire on every revolution of the engine.

I'm glad you made it without blowing the exhaust off your car.

Steve

So you're saying that the plugs are in series? And the head/block 'floats' wrt to the secondary? That means that pulling the wire from one plug would kill both cylinders. Are you sure about that?

You can kill both cylinders if you pull the correct wire, but not necessarily either wire.

I meant pulling either plug wire would kill both. If that's not the case, then they're not wired as Steve said.

Steve's description was accurate.

My only exception to what he wrote is in regards to whether a DIS system has the capability to detect power of waste firings... Saturn has used such a system since the mid 90s.

I still don't get it....

On mine, plug #3 had no spark period, yet the other tower on the same coil, #6 was sparking just fine?

Then when I hooked 'both' #6 and #3 to post #6, I got spark showing at both plugs... Post #3 was left open.

It did run worse like that though, under load....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

The problem with the coil was located very close to the #3 secondary terminal. When the magnetic field collapsed in the primary, high voltage was still generated in the secondary windings, assume that the #6 terminal is the negative side and the #3 is the positive side... Since there was a much greater voltage potential at the #6 terminal than there existed in the cylinder head, voltage flowed as it was supposed to.

It would be wrong to assume that there -has- to be a completed circuit with respect to the entire secondary loop as described by Steve, there only has to be enough -electrical potential- between #6 terminal and the cylinder head.

Had the coil secondary failed near(er) to the #6 terminal, both cylinders would have been dead.

The GM dis coils have a tendency to "tunnel" internally. The secondary arcs thru the plastic to ground or to the primary. Either condition is not good for the icm

Mike- When you hooked up both wires to the same coil tower, the spark could fire either plug. It wouldn't fire both at the same time. It would fire the easiest plug. That would be the waste plug. It takes far less voltage to jump the waste plug than the compression plug.

That would appear to be exactly what happened. It fired under no load, but messed up under load.

Man what a scam, 3 coils to replace now at $60.00 each instead of one or even the new ones with one coil per cylinder!

Mike