91 ZR-1 Cutting Out Under Load

[GregCrowe]

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:



Summit coil as shown on Summits website:



Summit coils they sent me:



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

[GregCrowe]

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 ?

[tccrab]

Originally Posted by GregCrowe

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

Jeff, what does this mean to you ?

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"

[GregCrowe]

Originally Posted by tccrab

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"

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.

[XfireZ51]

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.

[GregCrowe]

Originally Posted by XfireZ51

Greg,

Have you tried ohm'ing the coils from the positive and ground inlets at the bottom of the coils?

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.

Originally Posted by GregCrowe

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 ?

Connect the ohmmeter leads across the ignition coil primary terminals, and compare the primary resistance reading to specifications (GM asks for .35 - 1.45 OHMS). Then connect the ohmmeter leads across the coil secondary terminals and compare the secondary resistance reading to specifications (GM asks for 5,000-6,500 ohms).

Any replacement coil must be within the spec of the primary terminal.

GM does call out two different DIS coils. D545 and D555. The D545 is what they consider a replacement in the LT5. I would suspect that the aftermarket does make coils that are all inclusive. Check the primary readings and let us know what you find.

[GregCrowe]

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

Yes

[XfireZ51]

Originally Posted by GregCrowe

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

Greg,

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