question

[bamawrx]

Can anyone post a chart or tell me which cylinders share coil packs? For a 1990 in case that matters. I also need some recommendations for "must have" technical manuals. I also need to know the layout of the packs under the plenum identified by which cylinders they power. I tried to search the forum but it wouldn't work from my phone for some reason. Thanks for any assistance.

[Dynomite]

Can anyone post a chart or tell me which cylinders share coil packs? For a 1990 in case that matters. I also need some recommendations for "must have" technical manuals. I also need to know the layout of the packs under the plenum identified by which cylinders they power. I tried to search the forum but it wouldn't work from my phone for some reason. Thanks for any assistance.

Photo Provided by ZR1Vette (Coil Numbers Shown)

Service Manual Supplement (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070557)

http://i17.photobucket.com/albums/b79/MRBLU/ZR1Coilpacdetail.jpg

[bamawrx]

#6 wire is top right then. I'm going to see if I can trace its pair.

[bamawrx]

#6 wire is top left then. I'm going to see if I can trace its pair.

[Dynomite]

#6 wire is top left then. I'm going to see if I can trace its pair.

The only one left (I mean the only one you cannot see)....that would be bottom left in photo ;)

[bamawrx]

Ok so #6 is paired with #3. I just traced the wire. That is big help. I'm going to check continuity.

[Dynomite]

Ok so #6 is paired with #3. I just traced the wire. That is big help. I'm going to check continuity.

Looks to me like #6 is paired with #1 :confused:

drivers side bank from front to rear:
1 3 5 7

passenger side bank from front to rear:
2 4 6 8

Firing order is 1-8-4-3-6-5-7-2

[bamawrx]

Very odd. I just traced my #6 wire and its in the #2 position on your chart.

[Dynomite]

Very odd. I just traced my #6 wire and its in the #2 position on your chart.

let me check...This is identical.....I am now confused :confused:
Left side of photo is front of engine.

I assume your #6 wire goes to the Passenger side third cylinder from front?

When you say #2 position you are referring to the coil top right in photo (the pin extreme right) in photo?
Or are you talking Coil top left and pin top row in center of photo?

http://i287.photobucket.com/albums/ll142/dynomite007/91%20ZR1/ZR1Coils.jpg (http://s287.photobucket.com/user/dynomite007/media/91%20ZR1/ZR1Coils.jpg.html)

[bamawrx]

From your photo my car has #6 cylinder wire attached to your #2 label.

[bamawrx]

Which would be passenger side rear of engine.

[bamawrx]

Wouldn't #2 and #6 fire at same time?

[Dynomite]

From your photo my car has #6 cylinder wire attached to your #2 label.

Where is the #2 (front first cylinder on passenger side) wire attached? :p

Firing order is 1-8-4-3-6-5-7-2

[bamawrx]

Disappears deep under plenum. My best guess....the #6 spot.

[bamawrx]

I have no spark on six. Plug is carboned up. Marc suggested to use volt meter to check continuity between wire pairs to rule out bad wire verses pack. I hope its bad wire because I can change it without plenum removal.

[Dynomite]

Change plugs on number 6 plug wire....using good plug. You can change a plug wire without removing plenum?? :thumbsup:

1 and 6 fire with 1 TDC compression and 6 TDC exhaust.
8 and 5 fire with 8 TDC compression and 5 TDC exhaust.
4 and 7 fire with 4 TDC compression and 7 TDC exhaust.
3 and 2 fire with 3 TDC compression and 2 TDC exhaust.

Then we get to 1 and 6 again but this time 6 is TDC compression.

Drivers side bank from front to rear:
1 3 5 7

Passenger side bank from front to rear:
2 4 6 8

Firing order is 1-8-4-3-6-5-7-2

http://i17.photobucket.com/albums/b79/MRBLU/ZR1Coilpacdetail.jpg

[bamawrx]

Ok I was right about cylinder numbers. Definitely #6 wire in #2 spot. Any harm in leaving it there?

[Dynomite]

Ok I was right about cylinder numbers. Definitely #6 wire in #2 spot. Any harm in leaving it there?

I guess not since it is a waste spark ignition.......

[Franke]

I think the story goes that the cylinder under compression would fire and the other one would be wasted spark. Yes - No?

[Dynomite]

I think the story goes that the cylinder under compression would fire and the other one would be wasted spark. Yes - No?

Paul wrote a good description...of waste spark.

It's called a "waste spark" system. Cylinders are twinned, but only one at a time is in compression cycle when the spark arrives.

Just a point of interest: Because current flows in a loop through the block, coil and plug wires/plugs, the current is the same through both spark gaps. However, due to the much higher compression air pressure in the cylinder about to fire, the gap resistance to flow is much higher, resulting in the heat generated in the spark to be proportionately higher than that in the waste spark cylinder. In other words, the majority of the energy expended in the circuit is concentrated in the compression cylinder, resulting in very little actual "waste", really.

FWIW,

P.

[bamawrx]

I can reach the #6 plug at the coil due to its improper location. Marc told me just today that you can change the back four wires with plenum in place. Obviously I have not yet attempted this feat. Seems from your firing order info its no big deal. Certainly not worth pulling a plenum over.

[Dynomite]

I can reach the #6 plug at the coil due to its improper location. Marc told me just today that you can change the back four wires with plenum in place. Obviously I have not yet attempted this feat. Seems from your firing order info its no big deal. Certainly not worth pulling a plenum over.

OK...that makes sense on changing those back four plug wires from the rear of plenum......and if it is #6 actually connected to Coil #2....you can change that plug wire if after trying a good plug on that wire you get no firing.

[bamawrx]

We checked a good plug in the #6 wire while at Gordon Killebrews house on Sunday. Apparently you can use volt meter on, in my case, plug wires #6 & #3 and check ohms while turning engine over. If one wire is bad you should get half the ohms of good pair off same good coil.

[Schrade]

http://www.animateit.net/data/media/august2009/drool.gif

THAT looks RIGHT!!

(and mines' is gonna' too ;) )



Photo Provided by ZR1Vette (Coil Numbers Shown)

Service Manual Supplement (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070557)

http://i17.photobucket.com/albums/b79/MRBLU/ZR1Coilpacdetail.jpg

[Dynomite]

We checked a good plug in the #6 wire while at Gordon Killebrews house on Sunday. Apparently you can use volt meter on, in my case, plug wires #6 & #3 and check ohms while turning engine over. If one wire is bad you should get half the ohms of good pair off same good coil.

When I hit the starter....it STARTS unless you have ALL the Plugs removed :D

OK.....So....your good plug did not fire either when connected to #6 plug wire?
So....you did not have an open circuit on those plug wires you checked ohms?

I assume then the ohms you are reading turning the engine over is resistance of plug wire and coil?
What resistance do you read on a good plug wire/coil? Zero resistance minimum??

[bamawrx]

Engine would be running during test. If I understood Marc correctly you should see about 10000 ohms when testing a pair of wires off the same coil. A known healthy pair can be tested for comparison. If anyone is curious, just pop two wires off from same coil and report back the findings. I have to replace my volt meter before I can run the test.

[Paul Workman]

Schematic might help...

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/LT5coils-2.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/LT5coils-2.jpg.html)

[bamawrx]

Schematic clearly confirms the #1 and #6 should share a coil. Just got a new volt meter placed on my desk. Should have a result soon.

[bamawrx]

Result:

Since we are measuring resistance the engine is off for test. Set meter to Ohms and checked pair of wires off same coil. Got 10-14K, which is correct for good wires. Bad coil pack. Only got correct result with #1 and #6 wires, so car is correctly wired but with coil pack in different location than the charts.

[Schrade]

FSM for some years ('94, that I know of) says EMI (radiation similar to a nuke), can cause headaches, and come from mis-routed wires (grounding out through the insulation and not at the plug).

Whether or not fire SEQUENCE (apart from FO of course), and proximity of Coil Pacs makes a difference, I don't know. Hog, or Dave [WVZR1] might know...

Reading yours here makes me look at something I got in a different manner here - there's extra wire loom on some of my wires - looks like extra insulation against the IH - but it might be not only for physical wear protection, not electrical insulation - like the red highlighted one:

http://www.zr1.net/forum/attachment.php?attachmentid=2905&stc=1&d=1381949291

[bamawrx]

I have extra wire loom also, including the failed #6. Condition of wires "appears" new also. Wonder if grounding through insulation would show up in resistance testing.

Anyone think it would be a problem to drive this car about 50 miles nice and easy to shop?