Re: 91 ZR-1 Cutting Out Under Load
 

Jeff, is there anything special about the ZR1 coils? Are all these GM DIS coils the same?

edit: I'm finding that most all GM cars with DIS systems use the AC Delco D555 coil. For some reason, the ZR1 is listed as using the D545 which seems to be ZR1 specific. This has me suspecting the Summit Coils or any other standard coils may be a problem ??? But then again, just found another webpage with a GM replacement coil(Chinese like all the cheapies at Auto Zone and OReillys) saying it replaces BOTH the D555 and D545. I'm confused.

http://www.rmsautoparts.com/proddetail.php?prod=D545

http://www2.partstrain.com/store/?Nt...586&SID=1&cj=1

http://www.amazon.com/gp/product/B00...=A8F3HAQ1FDLH8

Further investigation finds the Accel coil:

http://www.car-stuff.com/store/image...cel/140017.jpg

Summit coil as shown on Summits website:

http://static.summitracing.com/globa...m-850017_w.jpg

Summit coils they sent me:

http://www.rpmmotorsportstulsa.com/Greg/Coils1.jpg

Notice how the coils Summit sent me don't match the pic on their website. Also notice that the Summit coils sent to me are exact copies of the Accel coils. The body is the exact same and these are the only versions that look like this. They also both have the gold terminals and both have the little side tabs that have to be ground off. Jeff, aren't you using the Accel coils? I'm 99% positive the Accels and Summits sent to me are the same thing.

Further edit: Sherlock Holmes scores........

BUSTED ! For sure the Summit coils sent to me ARE ACCEL COILS !
Notice the part number on the side of the Summit boxes: SUM-850017
Part number listed for the Accel coils : ACC-140017 http://www.accel-ignition.com/Produc...minselection=1

Re: 91 ZR-1 Cutting Out Under Load
 

I may not be doing this right so please correct me if I'm not but I measured the resistance on the stock coils at the 2 spark plug wire terminals. This is what I got:

1. 5.71 k-ohms
2. 5.61 k-ohms
3. no reading
4. no reading

Then I did the Summit/Accel coils:

1. 7.18 k-ohms
2. 7.24 k-ohms
3. 7.20 k-ohms
4. 7.26 k-ohms

Jeff, what does this mean to you ?

Re: 91 ZR-1 Cutting Out Under Load
 

While I am no JeffVette, it looks to me like you've found something.
Providing that you measured the coils exactly the same way, i.e., where you touched the contacts with the meter pins, then it would appear that coil pack 3 and coil pack 4 have gone open circuit.
Assuming that these coil packs are not functional or perhaps only marginally operational, you would have the worlds worst running 4 cylinder engine.

TomC
"Crabs"

Re: 91 ZR-1 Cutting Out Under Load
 

Yes, that's what I thought. I definitely don't have a 4-cylinder ZR-1. The car was(before the Summit coils) running fine when cold. I was shocked to not be able to get a reading from 2 of the coils. I must have went back 10 times and tried to get readings from them. Every single time, nothing. I suspect they must be marginal. Why the Summit coils made the car run like crap I still have no clue.

I'm waiting for Jeff to chime in but I'm thinking about going and buying 4 of the GM D545 coils.

Re: 91 ZR-1 Cutting Out Under Load
 

Greg,

Have you tried ohm'ing the coils from the positive and ground inlets at the bottom of the coils? The original Summit coils you showed look VERY MUCH like the MSD coils I have without the lettering. However all that doesn't explain why the stock coils still would produce a hesitation on acceleration. :confused:

Re: 91 ZR-1 Cutting Out Under Load
 

I tried but couldn't get my volt meter terminals to fit up in the slots and get any kind of a reading. I might try sticking some wires up there tomorrow and read off the wires.

Re: 91 ZR-1 Cutting Out Under Load
 

Re: 91 ZR-1 Cutting Out Under Load
 

When you say "primary reading", do you mean from the 2 little slots on the bottom of each coil ?

Re: 91 ZR-1 Cutting Out Under Load
 

Yes

Re: 91 ZR-1 Cutting Out Under Load
 

Greg,

Try fitting some spade lugs in the slots and then connecting Ohmeter to them.

Re: 91 ZR-1 Cutting Out Under Load
 

Spades wouldn't even fit up in those tiny slots. I did however use some wires.

Testing of the original GM coils got me:

Primary / Secondary
1. .6 ohms / 5.63 k-ohms
2. .6 ohms / 5.57 k-ohms
3. .6 ohms / zero
4. .6 ohms / zero

All the stock coils look fine on the primary readings. The secondary readings do look suspect.

I'll try to pull the Summit/Accel coils and get a primary reading on them today if possible.

Re: 91 ZR-1 Cutting Out Under Load
 

I bought a set of brand new GM ZR-1 D545 coils.

So.........More coils, more tests:

Summit/Accels :

Primary / Secondary
1. .7 ohms / 7.02 k-ohms
2. .6 ohms / 7.06 k-ohms
3. .6 ohms / 7.06 k-ohms
4. .7 ohms / 7.00 k-ohms

Brand New GM D545's

1. .5 ohms / 5.71 k-ohms
2. .5 ohms / 5.64 k-ohms
3. .5 ohms / 5.66 k-ohms
4. .5 ohms / 5.66 k-ohms

The one thing I did notice on the Summit Accel coils was that the slots on the bottom of each coil(that the 2 spade terminals plug into) were bigger and more loose than on the GM coils. They definitely don't make a nice tight connection. That may be the problem.

I should have the car back together tomorrow and we'll see if it's fixed.

Re: 91 ZR-1 Cutting Out Under Load
 

IT'S FIXED !!!!!!!!!!

Yes folks, my ZR-1 is running like a champ again. New GM D545 coils fixed the problem. The high rpm power is awesome. No cutting out, no miss, no falling on it's face.

For the record, let it be know that SUMMIT/ACCEL COILS SUCK !!!!!!

These are absolute JUNK !

http://www.rpmmotorsportstulsa.com/Greg/Coils1.jpg

I will be having a nice conversation with Summit tomorrow.

I would like to thank everyone out here for their help over the past 3 years and especially JeffVette.

Re: 91 ZR-1 Cutting Out Under Load
 

Congratulations Greg!!
The entire ZR-1 brotherhood applauds you!
Your perseverance, determination, and resourcefulness have finally paid off.
34 months, 173 posts, 8,600 looks later and the problem is now solved
....and at the end you got it right about the coils.
I almost picked up a set of Accels a while back for spares but went with the MSD 8224's instead. Just checked them and they meg out the same as your new set of GM D545's.

Re: 91 ZR-1 Cutting Out Under Load
 

Glad to hear Greg. Go and give summit hell.

Re: 91 ZR-1 Cutting Out Under Load
 

Is the LT5 coil a common GM part?

Re: 91 ZR-1 Cutting Out Under Load
 

Very common. GM D555 or D545. I have no idea what the difference is between the 2 part numbers. It's the same coil as used on almost every GM V6. 3 coils on the V6, 4 on the ZR-1 V8.

Re: 91 ZR-1 Cutting Out Under Load
 

I may have figured out the difference between the GM D545 vs the GM D555 coil. The D545 lists for 70 cents more than the D555. It looks like the D545 comes with a little rubber gasket a hair over an inch long that goes around the 2 pin connectors under the coil. From best I can tell, the D555 comes without the rubber gasket.

Re: 91 ZR-1 Cutting Out Under Load
 

Damn awesome !! Makes me feel better I changed out mine with GM replacements as well when I had the top end done. Damn gald to hear you chased that problem down!! I considered going the Summit route as well

Re: 91 ZR-1 Cutting Out Under Load
 

Good Job Greg!
:thumbsup:
I commend you for your perseverance.
:worship:
I personally would have given up hope after only a month or two, but you've hung in there for nearly 3 long years.
Simply Amazing.

Now, get in it and.....

DRIVE IT LIKE YOU STOLE IT!!!

Congratulations, my hat is off to you.
Long live the beast.

TomC
"Crabs"

Re: 91 ZR-1 Cutting Out Under Load
 

:occasion1:occasion1:occasion1:occasion1:occasion1 :occasion1

Re: 91 ZR-1 Cutting Out Under Load
 

Good deal Greg! :thumbsup:

You wouldn't happen to have the part number for the GM coils?

TIA
:cheers:
Tom

Re: 91 ZR-1 Cutting Out Under Load
 

D555: 10472401
D545: 10467067

Here's a great deal on the D555's:

http://cgi.ebay.com/ebaymotors/NEW-G...spagenameZWDVW

Re: 91 ZR-1 Cutting Out Under Load
 

Thanks Gregg!:thumbsup:


:cheers:

Re: 91 ZR-1 Cutting Out Under Load
 

Glad you got the Z running again:dancing.

I had a similar problem with mine. I switched to the Accel coils and the car wouldn't run very well when hot. I took it to DRM and Doug said that the Accels would fail because of the heat generated by the engine. He replaced with GM coils and the car ran just fine after that. Unfortunately that didn't solve my other problems but that's another story.:mrgreen:

Re: 91 ZR-1 Cutting Out Under Load
 

Greg, sure glad you nailed it and really glad you hung onto the car.
I am curious about the Summit coils. Did they take them back?
What size wires are you using? 7mm or 8mm?
Since the summit coils were not subjected to high temperatures I am curious about the failure mechanism. If the primary to secondary winding ratio is large enough over stock then the secondary voltage could be exceeding the insulator breakdown voltage of the wire insulation.
(hotter spark)
The measured resistance seems to indicate this but there are other explanations behind the measured values. (quality and diameter of wire)
I sure would like to cut one of those summit coils apart.
Root cause analysis stuff.
Thanks
Scott

Re: 91 ZR-1 Cutting Out Under Load
 

Yes, Summit took them back. I'm using new GM plug wires, think they're 8mm. I think the problem with the Summit/Accel coils was the 2 connection slots. They were too lose, didn't squeeze the terminals that plugged into them.

Re: 91 ZR-1 Cutting Out Under Load
 

Ok that makes sense. Good detective work. I put Accel coils in back in mid 2002 and have not had an issue. As I wrote earlier I did have a similar issue to yours with the stock ones but I believe two of them were defective (a few shorted windings) because they read lower resistance on the seconaries than the rest. One thing I did have to do was replace the stock wires with 8mm because they began arcing through the insulation with the Accels. I do remember having connection issues with the new coils on the input because they came with an orange rubber like gasket. The problem was some of the plugs on the wireing harness had the orange gasket still attached. That made for two gaskets and it would not make a proper connection.
Anyway, we're all glad I am sure that you're back on the road. Good timing too. Summer is knocking at the door.=D>

Re: 91 ZR-1 Cutting Out Under Load
 

What a great thread!

I pursued Greg's tip and purchased the "D555s" noted above, but I am not sure I want to install them now that I have them.

On these new units, the secondary windings are measuring 5.6 to 5.8K which is close to the GM recommended range of 5.6 to 5.7, but the primary windings are measuring 1.7 ohms - GM recommendation is .5 ohms. I am also a little suspecious of the part no on the replacements; it is 10482928 rather than the numbers Greg quoted above. I am thinking - don't think I will use these replacements. Am I being too cautious?

Re: 91 ZR-1 Cutting Out Under Load
 

Another too good to be true? Those are half the cost of AC delco direct from delco.

Re: 91 ZR-1 Cutting Out Under Load
 

I LIKE JERRY'S REPONSE TO MY QUESTION. I'D BE INTERESTED TO KNOW IF ANYONE ELSE HAS SOME WISDOM TO ADD TO THIS - APPRECIATED!

JERRY'S RESPONSE:

CAVEAT: I'm no expert on the subject but think I understand the principal according to the following tech article.

Transformers/Ignition coils

Transformers step-up (increase), step-down (decrease), or pass-through (same level) AC voltage or pulsed DC voltage. A basic power rule applies to transformers; power-in equals power-out. The unit of measure for Power is the Watt. 1 Watt = 1 Volt x 1 Amp.

A transformer has three main components:

An iron core - The iron core is wrapped with two separate coils of wire. The job of the iron core is to strengthen the magnetic fields of the transformer.

Primary winding - The input side of the transformer. This coil of wire is tightly wrapped around the iron core of the transformer.

Secondary winding - The output side of the transformer. This coil of wire is tightly wrapped around the primary winding of the transformer.
There are three basic types of transformers:

Step-up transformer - The primary coil winding has less windings of wire than the secondary coil does. A 1:2 step-up transformer has half as many primary windings as the secondary coil does. This means that if you apply 12V and 12A to the primary winding, approximately 24 V AC will be induced into the secondary winding, however, the output amperage will be cut in half to 6 amps.

Step-down Transformer. - The primary coil winding has more windings of wire than the secondary coil does. A 2:1 step-down transformer has twice as many primary windings as the secondary coil does. This means that if you apply 12V and 12A to the primary winding, approximately 6 V AC will be induced into the secondary winding, however, the output amperage will be doubled to 24 amps.

Pass-through transformer - In a 1:1 transformer, the primary coil winding has just as many windings of wire as the secondary coil does. This means that if you apply 12V and 12A to the primary winding, approximately 12 V AC will be induced into the secondary winding, and the output amperage will be 12 amps. The advantage of a 1:1 transformer is that there is not a direct electrical connection between the two coils. If one side of the circuit gets short circuited, the other side will remain isolated.

Examples of transformer use on automobiles:

Ignition coils - An ignition coil is an example of a step-up transformer, the primary coil input voltage is 12-15 V and the secondary output voltage is 20-60 kV. This means for every primary coil winding there are at least 2000 secondary windings. This also means that the output amperage will be at least 2000 times smaller than the input amperage. Secondary ignition voltage is high voltage, but amperage is low.


Quote:
.....the primarly windings are measuring 1.7 ohms vs the .5 ohms specified by GM. The secondary windings seem ok (the new ones are measuring 5.6K to 5.8K which is close to the 5.6-5.7K quoted by GM).

Since only resistance is known and number of windings is unknown, I assume that winding wire size & type is the same, therefore resistance is a function of length of wire in the windings.

I interpret your findings to show that the resistance of the primary windings in the eBay coil is 3.4 times that of the OEM LT5 coil, meaning it has more windings. If the resistance of the primary windings is higher and the secondary windings resistance is the same, that means the voltage output would be lower than the OEM LT5 coil, i.e. coil discharge voltage is not as high as the OEM LT5 coil.

My non-expert opinion, don't use them. The spark is not as hot.

However, I do have my flame suit on![IMG]http://images.ibsrv.net/ibsrv/res/src:forums.*************.com/get/images/smilies/lol.gif[/IMG] END OF JERRY'S TAKE

Re: 91 ZR-1 Cutting Out Under Load
 

Generally I’d have to agree with the functional description of a transformer entered. However, there are a few assumptions that cannot be made. Some matter some don’t. The core of the transformer may not be iron. It’s probably a composite ferrite. That does not matter.
But to assume the diameter of the primary wire is the same as the GM part may be a mistake. Assuming this was done on purpose as a method of increasing reliability it may be that a smaller diameter wire was used. This would make it possible for the manufacturer to use the same number of windings but draw less power. Less power would mean less heat internally. Less heat at the windings could translate to fewer shorts between windings. This is pure speculation on my part but I’d guess the higher primary winding resistance was done on purpose.

Generally using winding resistance is a poor way of judging coil quality. While differential resistance between like type parts is better than nothing a truer measure would be output voltage swing measurements. And what’s more doing this measurement while the coil is at high temperature would be a great test. I am not sure of what the major failure component would be on these coils but I am guessing either internal shorts OR high voltage arching internally. An internal arching problem is not likely to show up on a static resistance measurement.

What I’ve read about the Summit and Accel coils on this thread does not confirm to me that they are bad. If the primary connectors were not pinching the spade end of the car’s connection addequately that is easily fixed my squeezing them together before assembly. Such a failure does not mean the coil cannot produce the needed output voltage. Of key importance on these coils is longevity at the temperatures in the engine valley that the LT5 has.

I’d sure like to get my hands on a coil that fails. Even better, one that reportedly fails on only one side. That is, each coil sparks two cylinders each time if fires. (one is on exhaust stroke the other on compression) On a failure such that only one side fails it should be possible to swap the two plug wires right at the coil and see the failure move to the other cylinder. Yah, that would be a lot of plenum work :icon_scra

Re: 91 ZR-1 Cutting Out Under Load
 

Yes, I found out this guy up East is misrepresenting these coils as new. They are just take-offs from who knows what. I bought a set from him and promptly sent them back when I found out what he was doing.

The coils I installed on the car were real new GM D555's in GM boxes from O'Reilly Auto Parts.

Re: 91 ZR-1 Cutting Out Under Load
 

:dontknow:You gotta make some assumptions somewhere as a starting point or it's going to turn into a book no one wants to read. I think you even made an assumption:dancing