STILL NO SPARK ON TWO CYLINDERS

[SDZR-1]

Before I disassembled my top end for a starter and injector replacement I had checked for spark to all cylinders...everything was good. While my plenum was off, I decided to change wires and plugs. After reassembly the car was still running a bit rough, but it was definately a different rough than prior to injector replacement. After checking for spark I determined that cylinders 2 and 5 had no spark to the plug. I figured the only logical explanation for this was that I had a bad coil, so pulled everything apart to install coilpacks when I discovered that 2 and 5 werent even on the same coil and was a little confused....but I put it back together still hoping that it was more than one coil or something of the sort. I was sadly disappointed when it sounded no different than prior to coil replacement and cylinders 2 & 5 still had no spark....I am very very frustrated at this point (and trying to hold my temper back and used it on someone who deserves it...haha) because now I am looking at doing a 3rd plenum pull to figure this all out. The only other idea I have is that the plane that the coils mount to has shorted out....but dammit, I want to be sure this time so was hoping someone had somewhat of a similar experience. So if this is what my problem is....how much more cash am i gonna have to shell out, this is getting rediculous...what a way for a zr-1 to welcome it's new owner.....I guess it ran well for my 1500 mile journey home, so at least I didnt experience these probs on the road.

thanks,
Jarvis

[guinnessdood]

Jarvis,

Have you checked the new wires for proper resistance? Maybe you got some bad wires? Or more likely some bad ends on the wires...check them out. Are you certain that it's NO spark and not NO Fuel? If the connector on the injector is not all the way on...no fuel. What wires/plugs/injectors did you buy? Right now I am betting on the injector connectors. I had one that was not all the way on when I changed my injectors (Accel) (ran like crap on 7 cylinders)...I was able to get to it with a flathead screwdriver and push it the rest of the way on. If you bought Accell or MSD injectors the nub on the primary injectors need to be ground off to get the connector to fit properly.

[SDZR-1]

Jarvis,

Have you checked the new wires for proper resistance? Maybe you got some bad wires? Or more likely some bad ends on the wires...check them out. Are you certain that it's NO spark and not NO Fuel? If the connector on the injector is not all the way on...no fuel. What wires/plugs/injectors did you buy? Right now I am betting on the injector connectors. I had one that was not all the way on...I was able to get to it with a flathead screwdriver and push it the rest of the way on. If you bought Accell or MSD injectors the nub on the primary injectors need to be ground off to get the connector to fit properly.

No...havent check wires for resistance...but thought it would be odd to have two at once since they were new. I installed accel injectors, delco wires and plugs. There was no spark going through either wire when I pulled them off I heard no spark and also no spark to a screwdriver when placed near the wires end. Also, I did grind the nub off of the primary injectors. I am pretty certain that all of the connectors went on all the way because i specifically listened for each of them to click when the wire holder fell into place on the injector. thanks for the quick reply.

[guinnessdood]

No...havent check wires for resistance...but thought it would be odd to have two at once since they were new. I installed accel injectors, delco wires and plugs. There was no spark going through either wire when I pulled them off I heard no spark and also no spark to a screwdriver when placed near the wires end. Also, I did grind the nub off of the primary injectors. I am pretty certain that all of the connectors went on all the way because i specifically listened for each of them to click when the wire holder fell into place on the injector. thanks for the quick reply.
Jarvis,

Do you have a Factory Service Manual? http://www.helminc.com/helm/Result.asp?Style=&Mfg=GMC&Make=CHV&Model=CVET&Year=1990&Category=&Keyword=&Module=&selected%5Fmedia=&mscsid=L9QQR6XNNXDW9JPBSWH2AE6VM2S42BJ4

If not...you should get one from the link above or on eBay. Best money you will spend on your Z. Make sure you check all of the things I mentioned and hit us back....we'll get it figured out...can't be anything too serious. You could always try swapping coil packs around too...see if it changes cylinders. I know that removing and replacing the plenum gets old...just gotta have patience. BTW...if you do the throttle body coolant bypass that saves some time and hassle. Do you drain your coolant resivoir? That helps too. I am speaking about making the plenum pull a little easier. Are you plenum gaskets in good shape? Hope so...they're not too cheap.

[Jeffvette]

OK, I'm going to get on a soap box here.

We have a lot of guys who are pretty bright, know their way around a LT5 and can help troubleshoot a car over a vast distance, which is fairly difficult. The only bad thing is when the owner of the car does not fill us in on what has been changed or been found. Had you mentioned the plugs on 5 & 2 where the suspect coils, we could have told you they were not a grouped pair. You did not make any mention of brand new plug wires in your previous posting.

I will add this, the grounding plane is not a high failure rate part. I have only come across it once. If it is bad, I have a spare part that you can borrow, as it is no longer available from GM. But cylinders 5 & 2 do share a common connector going from the DIS to the ground plane. Dark Green and yellow wire coming out of the DIS connector.

[tccrab]

Sounds suspiciously like the problem that I had last year after I replaced my fuel injectors.....
http://www.zr1netregistry.com/forum/showthread.php?t=2206

Good luck!

[SDZR-1]

Dark Green and yellow wire coming out of the DIS connector.

Are you referring to this as a single wire that is colored dark green/yellow....or as two different wires (1 green, 1 yellow)?

[SDZR-1]

Sounds suspiciously like the problem that I had last year after I replaced my fuel injectors.....
http://www.zr1netregistry.com/forum/showthread.php?t=2206

Good luck!

Well as luck would have it, there are 4 other zr-1's in my tiny little town of 350 ppl. I bet I could borrow an ecm just to determine if that is my problem. 3 of these are sitting in our shop, but the '91 isnt as easy to access as it is in the trailer...is a 90 ecm the same, or should I be certain to try to 91?

Oh, mine's a 91 btw.

Thanks everyone,

Jarvis

[guinnessdood]

Well as luck would have it, there are 4 other zr-1's in my tiny little town of 350 ppl. I bet I could borrow an ecm just to determine if that is my problem. 3 of these are sitting in our shop, but the '91 isnt as easy to access as it is in the trailer...is a 90 ecm the same, or should I be certain to try to 91?

Oh, mine's a 91 btw.

Thanks everyone,

JarvisJarvis,

Jeff was referring to ONE single wire. You can swap in the 90 ECM...but you need to swap in your 91 PROM into the 90 ECM. There is a plate on the bottom of the ECM with a bunch of small screws. Take off the plate and there sits your PROM. Don't try the 90 ECM without swapping in your 91 PROM...they are different.

[Kevin]

Stupid question, how did you determine you didn't have spark?

[SDZR-1]

Stupid question, how did you determine you didn't have spark?

took plug wire off of plug and listened for spark....didnt hear any, so pulled the wire out, stuck a screwdriver in the end to double check that way. I had nothing on either cylinder.

[Kevin]

I was going to suggest arking off the block but the screwdriver does the same thing. Coils rarely go bad.

[SDZR-1]

OK...I swapped ecm's w/ another 91 and it didnt change anything...so what next?

[Kevin]

OK...I swapped ecm's w/ another 91 and it didnt change anything...so what next?
Start checking injectors

[SDZR-1]

i've replaced all...and have tested, they all work.

[Kevin]

are the connections all good?s

[SDZR-1]

are the connections all good?s

yes...i specifically listened for the metal retainer to click on each one of them.

[tccrab]

It will only be one of three things, air, spark or fuel.
You can rule out air so that leaves spark or fuel.
Idle the car for a little while then pull plugs #2 & #5. If they're wet then you know for sure that you've got fuel.
You've swapped ECM's so you can rule out a problem with ECM injector drivers, but this does not rule out a problem with your PROM. See if you can borrow one of those too.

So that leaves spark.
Check the gap on your plugs. Are they the right plugs? Do the spark plug wires make good connection? Do you have the right wires going to the right plugs? (stupid question, but you gotta ask)
Buy a NOID, you can find them at your local parts store:
http://www.drivewerks.com/catalog/shopcart/TOOL/POR_TOOL_CAT447_pg28.htm
This will tell you for SURE if you've got spark at the plugs.
Change the order of the coil packs, see if the miss follows the coils. This will tell you if it's coil related or if it's signal related. ( I know this means pulling the plenum...again...)
While you've got the plenum off, be sure to measure the spark plug wires with an ohm meter, make sure they're all fairly close in ohms. You might have bad wires (not likely).
Closely examine the DIS module and it's connectors. JeffVette has already ID'd the one likely culprit wire.
I dont' know off hand how to diagnose the DIS module, maybe someone else can chime in on this.
If the problem is deeper it might be time to take it to a PRO.

[SDZR-1]

It will only be one of three things, air, spark or fuel.
You can rule out air so that leaves spark or fuel.
Idle the car for a little while then pull plugs #2 & #5. If they're wet then you know for sure that you've got fuel.
You've swapped ECM's so you can rule out a problem with ECM injector drivers, but this does not rule out a problem with your PROM. See if you can borrow one of those too.

So that leaves spark.
Check the gap on your plugs. Are they the right plugs? Do the spark plug wires make good connection? Do you have the right wires going to the right plugs? (stupid question, but you gotta ask)
Buy a NOID, you can find them at your local parts store:
http://www.drivewerks.com/catalog/shopcart/TOOL/POR_TOOL_CAT447_pg28.htm
This will tell you for SURE if you've got spark at the plugs.
Change the order of the coil packs, see if the miss follows the coils. This will tell you if it's coil related or if it's signal related. ( I know this means pulling the plenum...again...)
While you've got the plenum off, be sure to measure the spark plug wires with an ohm meter, make sure they're all fairly close in ohms. You might have bad wires (not likely).
Closely examine the DIS module and it's connectors. JeffVette has already ID'd the one likely culprit wire.
I dont' know off hand how to diagnose the DIS module, maybe someone else can chime in on this.
If the problem is deeper it might be time to take it to a PRO.

when I swapped ecm's, i took the whole thing from the other car including it's prom (which was also a 91). As far as checking plugs after running...I have done that - - -and yes, they are wet...so that leaves spark. The plugs are correct, the gap is correct....just not getting any spark through the wires. I changed each wire one at a time measuring each old one w/ a new one of the same length. I just dont know how badly I want to pull everything apart and going in blind. Perhaps I'll have to load it up and take it to a shop, but at this point I doubt they would know much about the car and I'd end up w/ one hell of a labor bill. Just hanging around the forum here has taught me many things and I appreciate every bit of everyones help and advice.

[guinnessdood]

Marc Haibeck has a DIS module he loans out if you think that could be the issue. www.zr1specialist.com of course if you have a ZR-1 there and the owner will let you remove the plenum...then that would work too....the DIS module is mounted on the underside of the plenum.

[SDZR-1]

I highly doubt he would want me to remove his plenum on either car....they're trailer queens. I might call mike and talk w/ him about it, I'm just getting frustrated w/ the plenum removal...btw, I probably dont want to use that plenum gasket too many times do I?

[tccrab]

My plenum has been on and off three times with the same gaskets and it still seals just fine. I think.
:mrgreen:

Tom

[SDZR-1]

But cylinders 5 & 2 do share a common connector going from the DIS to the ground plane. Dark Green and yellow wire coming out of the DIS connector.

Could someone tell me which page/section would have a diagram that shows where this "green/yellow" wire is at? I have looked and dont seem to find it, which probably means I'm blind or not looking in the correct section or page. This is sounding like it has to have something to do w/ my problem...I chatted w/ Marc Haibeck about it for a bit today and he says that it's definately not the DIS Module since one part of the coil is working...that means its doing its job since the coil either has power or does not, period. The odds of two brand new coils behaving exactly like the ones I replaced is highly unlikely so I have pretty much ruled them out. If I can find this wire, I would just like to check it for continuity to make sure the wire itself is good and not broken inside or something, and also make sure it is connected securely to where it is supposed to be.

Thanks,
Jarvis

[Jeffvette]

In the 90 manual it's on page 6E3-A-7 Complete mark up of the DIS wiring.

[SDZR-1]

Thanks Jeff!!:thumbsup:

[SDZR-1]

ok...so I've goofed - When I said that my car was not firing on 5 & 2....it was really not firing on 1 & 6. I was just numbering my cyliders starting from the oposite side of the engine and realized my goof when i was searching in the book. So at least 1 & 6 are on the same coil, so perhaps I can narrow it down to that area at least. I was getting the same reaction from the old coilpack versus the new one...so I dont think it is the coil. What I have done tonight was pull the plenum back off to check my wires from the coils to the DIS module for continuity...which all checked out good. All connectors look good as well. So I am stumped again, I really think the only other explanation is the DIS Module, even though it has been stated that they are not very likely to fail. I know that someone mentioned that I could possibly borrow one to determine if this was my problem, but that still means an additional plenum pull and as you can imagine I'm getting a little tired of doing that by now. Is there any way to determine if the module is bad by inspecting it or is there some way to test it electronically? Also, is there anything else I need to be checking/addressing to determine my issue? Thanks all.
Jarvis

[SDZR-1]

I am probably the happiest guy in the world right now as I have finally got my zr1 fixed. My problem ended up being the ignition module, so ANOTHER $400 later it was fixed...sure beat the crap out of gm's $900 unit. It was a pretty long road to go down and I hope I never have to take that route again. But anyway, just wanted to follow up so that this thread might be useful to someone else someday.

Thanks for the help and advice guys...much appreciated

Jarvis

[tccrab]

:cheers:
:thumbsup:
Congratulations!

Now, get in it and Drive It Like You Stole It!

:iroc:

Where did you find the igntion module for such a good price?

[jonszr1]

Congrats on the fix. Now go find a place to do some 7000 rpm blasts and clean her out and give you one of these:mrgreen: :mrgreen: :mrgreen: or 2 or 3

[SDZR-1]

Where did you find the igntion module for such a good price?

Got it from white racing...used obviously.

I took it out last night for a bit after everything was back together....but just didnt wanna push it too fast figuring that with my luck I'd hit a deer or something after just getting it fixed.

[Tim]

Glad to here that Jarvis. Just took a ride to Deadwood this weekend and when I passed the sign to Bison I thought of your troubles and hoped you resolved them. Needles highway and Iron Mountain Road were awesome for color and sights this time of year and gave me a chance to get up on the wheel a bit. Got some great videos.

[SDZR-1]

Glad to here that Jarvis. Just took a ride to Deadwood this weekend and when I passed the sign to Bison I thought of your troubles and hoped you resolved them. Needles highway and Iron Mountain Road were awesome for color and sights this time of year and gave me a chance to get up on the wheel a bit. Got some great videos.

yeah, I havent been through there in quite awhile...definately not w/ this car yet. I used to live in that area and I agree it is pretty amazing. Where are you from btw?