4-7 firing issue; posting for a member

[LGAFF]

Got somone in the registry having issues:

4-7 not-firing

Has replaced the DIS with no change


If I were guessing, and coil has been changed, I would think he has a bad wire from the bottom the DIS(Dark Blue Cir #932)....he was informed 2nd DIS was bad, but I would think thats a long shot...

Thoughts?

[phrogs]

wiat a second,

Does he get spark?

I had a missfire and it ended up being the ECM was not firing the injectors.

I had spark but no fuel took me a while to figure it out.

[scottfab]

Simply not enough to go on.
Guesses would be
Bent pin from DIS
bad wire on 4 or 7
bad coil
Bad connector at coil
shorted plug on 4 or 7

How is it that 4 and 7 were diagnoses as not firing?

[LGAFF]

I had bent pin on my list also, car was checked out at a GM dealer, however I am guessing that does not always mean much. Was curious to see what else other thought....I just cannot see it being a bad DIS

[XfireZ51]

Got somone in the registry having issues:

4-7 not-firing

Has replaced the DIS with no change


If I were guessing, and coil has been changed, I would think he has a bad wire from the bottom the DIS(Dark Blue Cir #932)....he was informed 2nd DIS was bad, but I would think thats a long shot...

Thoughts?

2 DIS modules bad?? And on the same coil???

[LGAFF]

thats exactly why I think something is not right here, has to be something else...I almost have to take bent pin off the list due to the fact 2 DIS used....thinking wire

I want to say they tried different coils

[scottfab]

thats exactly why I think something is not right here, has to be something else...I almost have to take bent pin off the list due to the fact 2 DIS used....thinking wire

I want to say they tried different coils

I think I'd be swapping plugs, wires and coil with
one of the other pair in the car.
Bad DIS again? Maybe especially if it was forced
to fire into a shorted coil.
This could be annoyingly time consuming to isolate.
Fortunately you can do end to end wire tests on
the harness that runs to the coil from the DIS.
I take it there is no spark at all on 4 or 7 ?

[LGAFF]

Sounds like it had been some time since he tried to address, I will see what notes he has....

[XfireZ51]

Some of you may recall that a few years ago I played around with using LSx coils on the LT-5. Basically I subbed LSx coils for the LT-5 coils and used the DIS module as the sequencer. Went through several iterations of that and actually got the motor to idle (and smoothly btw) for about 30-45sec before I blew a fuse for the Inj 2 circuit which supplies power to our coils. I tried 2 different types of LSx coils including the more "powerful" truck coils w heat sinks. Those did not work. When I first started the motor with the LSx coils it ran like crap until I discovered that the coils where cross wired. 3-5/4-6 were flipped. Motor ran albeit missing badly. With that cleared up, motor started great and ran until power blew out. I thought I may have had a couple of shorted coils also and subbed the upgraded truck coils along with some changes to the circuit including separate BATT (20a) and GND circuits for each bank of coils. It would start but not run. IOW, the DIS was starting the motor but the handoff for timing control to the ECM wasn't happening once it would reach 400rpm.
Got everythng back to stock eventually and DIS has been running ever since. The DIS should survive firing even a shorted coil because it is "current limited". Obviously the engineers that designed the IM took into account contingencies and malfunctions and safeguarded the IM from them. If all else fails the IM is what provides the "limp home" capability since it is essentially a CO-ECM. That's also what makes it difficult to substitute for without some great expense. Anyway, I bring this up to illustrate the ruggedness of the DIS module. Its probably the last thing to consider when having ignition problems since everything else will fail before the DIS does.

BTW, here's a shot of the LSx coils installed:

http://i187.photobucket.com/albums/x198/Z51Xfire/LS-2%20Coils%20Installed/LS2coilsmounting006.jpg

http://i187.photobucket.com/albums/x198/Z51Xfire/LS-2%20Coils%20Installed/LS2coilsmounting005.jpg

[LGAFF]

Looks like the things to check for this member

#DIS to Ign coil wire circuit 932(blue) for short(highest probability)
#swap ign modules
#make sure there are not too many rubber gromments on the module housing
#check continuity of module housing..

[scottfab]

.... snip....
The DIS should survive firing even a shorted coil because it is "current limited". Obviously the engineers that designed the IM took into account contingencies and malfunctions and safeguarded the IM from them. If all else fails the IM is what provides the "limp home" capability since it is essentially a CO-ECM. That's also what makes it difficult to substitute for without some great expense. Anyway, I bring this up to illustrate the ruggedness of the DIS module. Its probably the last thing to consider when having ignition problems since everything else will fail before the DIS does.
.... snip...


I wouldn't take this to the bank. It'll bounce.
I have a DIS from Mark H that I've examined in detail.
Any current limiting the DIS has still generates significant
heat which takes out the output FET(s) eventually.
If anyone would care to setup an experiment demonstrating
the DIS working into a dead short I'd be very interested.

[Blue Flame Restorations]

He could use a DIS checker if he has access to one.

[XfireZ51]

I wouldn't take this to the bank. It'll bounce.
I have a DIS from Mark H that I've examined in detail.
Any current limiting the DIS has still generates significant
heat which takes out the output FET(s) eventually.
If anyone would care to setup an experiment demonstrating
the DIS working into a dead short I'd be very interested.

Ask Marc H how many DIS' he has had to replace over the last 12+ years.
Also what's the likelihood of a coil going dead short before it goes weak?

[A26B]

He could use a DIS checker if he has access to one.

I could use such a device to check out a couple of DIS modules.

[scottfab]

Ask Marc H how many DIS' he has had to replace over the last 12+ years.
Also what's the likelihood of a coil going dead short before it goes weak?

I don't think that many fail but they can be killed.
I've personally never seen a dead short on a coil primary side.
Wires can get pinched though. The failure on the FET will be different
depending on heat vs voltage pop through. If a short is to a 12v supply the
N-channel will open up. Or if an arch from the secondary get into the primary same thing. Biggest failure is heat damage due to poor heat exchange into the plenum. I sure hope his failure is not the DIS.
Other things are cheaper.

[Blue Flame Restorations]

I could use such a device to check out a couple of DIS modules.


Jerry, the unit was Tyler's. We used it while getting the 88 EX5023 to run. Give him a shout.

[Jason 91]

First off, I would like to thank LGAFF for posting this up based on our conversation Saturday night. I'm the member who is having the issue and I appreciate the conversation and ideas on this.

I loved driving this car when it ran well, but this issue has been very frustrating. Mainly because I don't have the expertise to figure it out on my own and I've taken the car to local shops relying on their know-how or lack thereof.

This started awhile back when a couple of the injectors were marginal and it was suggested that I replace them which I did. The car actually ran worse after the injector change so the coil packs and spark plugs were changed at my request, but this didn't make a difference. I finally picked up the car from the guy who couldn't pinpoint the real issue.

The car was due for an emissions test and I took it in. It failed, of course, and I should have known it would have.

From here, I took it to a local Chevy dealership north of Denver which prides itself on Corvette sales and service. They quickly diagnosed it as a bad ignition module and said that they double checked everything because these can't be found.

I called Kurt at White Racing who suspected that this wasn't my issue and was thinking it was a bad ECM. So he shipped the ECM and this didn't fix the issue. He sent me the ignition module which didn't solve the issue either. Kurt accepted returns on both of these items, as a note.

When I went to pick up the car, I talked to the technician and service advisor who assured me that they checked everything possible that they could think of twice. At this point, the dealership made it clear to me that I needed to pick up my car and pay for the bill since they had my car now for over one month (due to back and forth trying new parts and locating an ignition module) and there was nothing more they could do for me until I found a good ignition module. In fairness, I'm sure that this is a standard practice given the time they had the car, but it simply added to the frustration.

I called and requested an emissions waiver on the car given what I had spent to try to get it running right and the ignition module availability. I was denied and told that this car is common and there are parts everywhere. It was even asked of me if I had tried AutoZone.

I'm going to try another repair shop here locally and see if I can get someone to work with me through this issue. I’ll pass along your collective thoughts. And if anyone has any ideas on local places to use, please let me know. Like I said above, I just don’t have the expertise and haven't found a consistently good technician since moving to Colorado several years ago.

This has been very frustrating, as I'm sure you can imagine. Thanks for the ideas and support here.

Jason

[XfireZ51]

Jason,

Save ur money and ship it to Chicagoland. The FBI will take care of it.

:dancing:handshak:

[Blue Flame Restorations]

Jason,

Save ur money and ship it to Chicagoland. The FBI will take care of it.

:dancing:handshak:

Best advice you'll get. They can get it fixed.

[scottfab]

I don't know. I think there's got to be a cheaper way to isolate and fix this besides shipping it half way across the country.
If you're willing to systematically go through a set of steps and learn to do somethings yourself, you'll not only learn along the way but you'll pick up a few tools to continue fixing things later.

So you have to ask yourself. Do you want to dive in and get you hands really dirty?
If not start looking at shipping charges or be willing to drive it to the windy city.

[tccrab]

Ran into a problem similar to this a few years ago.
The short story is, in testing fuel injectors I had stuck my Volt Meter probe into the female sockets of the ECM plug and in doing this I had stretched out the connectors such that they didn't make good contact with the male ECM pins any more.
http://www.zr1.net/forum/showthread.php?t=10828

Maybe, just maybe, somewhere along the way somebody did something similar to your ECM plug.

'Crabs

[GOLDCYLON]

Secondary driver modules is another place to check since she is a 91?

[Tyler Townsley]

I loved driving this car when it ran well, but this issue has been very frustrating. Mainly because I don't have the expertise to figure it out on my own and I've taken the car to local shops relying on their know-how or lack thereof.

I'm going to try another repair shop here locally and see if I can get someone to work with me through this issue. I’ll pass along your collective thoughts. And if anyone has any ideas on local places to use, please let me know. Like I said above, I just don’t have the expertise and haven't found a consistently good technician since moving to Colorado several years ago.

This has been very frustrating, as I'm sure you can imagine. Thanks for the ideas and support here.

Jason

Jason call Rod DeWild in Denver 720-284-4965 he has the expertese to help you, before moving on to LS7's he had SEVERAL 4 cam twin timing chain LT5 / ZR1 motors including a 427 cu in version running an automatic.

Tyler

[scottfab]

....snip....
I take it there is no spark at all on 4 or 7 ?

If you have spark..... yes pursue the fuel angle.
Maybe your authorized cheby dealer put the wrong injectors in?
Or otherwise did not get the connectors on right on the injectors?
Time to get dirty my friend.
Or find a friend that works the tools for you.

Bottom line is you have a ZR-1 that is ill and we want it
back on the road healthy. [-X

[tomtom72]

I know that this is off the wall....but after an injector r&r on Jim's car, I may be wrong on who owned the car, a miss developed. It got tracked down to a pinched wire in the injector harness. I think it got pinched between the I/H and the plenum upon reassembly.......just thought I'd toss that out there.


Mr. DeWild also said the same thing about our DIS modules when I bought a spare from his stock pile of LT5 parts.....just a fwiw.


:cheers:
Tom

[XfireZ51]

scottfab,

I emailed a friend, whom I respect a great deal, about the DIS module.
Here is his response regarding the dead short coil

"Dominic,

The shorted coil will put a large load on the driver. Even current limited, with the coil shorted it won't take any of the load. The entire load will be in the driver which will cause it to heat up excessively."

So you were correct with your assessment although I'd still consider the likelihood to be negligible.

[Pete]

First off, I would like to thank LGAFF for posting this up based on our conversation Saturday night. I'm the member who is having the issue and I appreciate the conversation and ideas on this.

I loved driving this car when it ran well, but this issue has been very frustrating. Mainly because I don't have the expertise to figure it out on my own and I've taken the car to local shops relying on their know-how or lack thereof.

This started awhile back when a couple of the injectors were marginal and it was suggested that I replace them which I did. The car actually ran worse after the injector change so the coil packs and spark plugs were changed at my request, but this didn't make a difference. I finally picked up the car from the guy who couldn't pinpoint the real issue.

The car was due for an emissions test and I took it in. It failed, of course, and I should have known it would have.

From here, I took it to a local Chevy dealership north of Denver which prides itself on Corvette sales and service. They quickly diagnosed it as a bad ignition module and said that they double checked everything because these can't be found.

I called Kurt at White Racing who suspected that this wasn't my issue and was thinking it was a bad ECM. So he shipped the ECM and this didn't fix the issue. He sent me the ignition module which didn't solve the issue either. Kurt accepted returns on both of these items, as a note.

When I went to pick up the car, I talked to the technician and service advisor who assured me that they checked everything possible that they could think of twice. At this point, the dealership made it clear to me that I needed to pick up my car and pay for the bill since they had my car now for over one month (due to back and forth trying new parts and locating an ignition module) and there was nothing more they could do for me until I found a good ignition module. In fairness, I'm sure that this is a standard practice given the time they had the car, but it simply added to the frustration.

I called and requested an emissions waiver on the car given what I had spent to try to get it running right and the ignition module availability. I was denied and told that this car is common and there are parts everywhere. It was even asked of me if I had tried AutoZone.

I'm going to try another repair shop here locally and see if I can get someone to work with me through this issue. I’ll pass along your collective thoughts. And if anyone has any ideas on local places to use, please let me know. Like I said above, I just don’t have the expertise and haven't found a consistently good technician since moving to Colorado several years ago.

This has been very frustrating, as I'm sure you can imagine. Thanks for the ideas and support here.

Jason


Jason,since you tried IM and ECM with no luck then i have 2 questions

Where/who's injectors did you buy/install?
I have found a few stock new injectors that were bad.
The pinched wire is also very doable.

What coils did you buy/install?
There were issues with some performance aftermarket coils.

I know it's frustrating but trust me it's something silly.
Pete

[Jason 91]

I thought that the injectors were RCs, but they actually came from Fuel Injector Connection. The coils are factory and were bought from the dealership.

#4 and #7 have no spark for certain. I was reading further through the FSM tonight (Chart C-4) and it seems like the diagnostic flow goes quickly to a faulty ignition module. I’m a novice (at best), but I can see where if someone wasn’t thorough they might jump to this faulty ignition module conclusion.
Thanks for the ideas you guys are providing here. There’s a lot to be looking for that could be simple and I really hope it is at this point.
Jason

[Jason 91]

Tyler, I also meant to mention that I reached out to Rod DeWild today and left him a message.

LGAFF, you mentioned this guy as well Saturday when we talked. I was thinking of someone else when I mentioned that I thought I knew him.

Thanks,

Jason

[ZZZZZR1]

I thought that the injectors were RCs, but they actually came from Fuel Injector Connection. The coils are factory and were bought from the dealership.

#4 and #7 have no spark for certain. I was reading further through the FSM tonight (Chart C-4) and it seems like the diagnostic flow goes quickly to a faulty ignition module. I’m a novice (at best), but I can see where if someone wasn’t thorough they might jump to this faulty ignition module conclusion.
Thanks for the ideas you guys are providing here. There’s a lot to be looking for that could be simple and I really hope it is at this point.
Jason

Are the injectors yellow / orange? If so they are FIC's rebuilt injectors and you should test to see if they work. (rebuilt ones are known to fail too)

You should be able to see the injectors without pulling the plenum.

:cheers:

David

[Pete]

Yeap injectors,i initially wrote and guessed that you had FIC's but removed it. LOL
There have been a few ZR-1 guys on here that had FIC injector issues.

Jason don't spend another dime just borrow a set of good injectors from someone and install yourself if all is good then order new Accels

http://www.jegs.com/i/Accel/110/150821/10002/-1
All of the FBI Z's have Accels never had one issue with them and 3 of them are big inch 10 second Z's.

You saved a few bucks on injectors but spend it elsewhere and now will spend more to replace them.Penny smart dollar foolish.

FIC will warranty them the issue i have is the 2 hour labor, $75 gaskets and all the frustration is just not worth the savings for used injectors.

Pete

[-=Jeff=-]

Yes I had/have FICs.. they are rebuilt. I had issues at first but now I have had them on for 4 years.. so far so good. I did have a couple leakers at first and I think I was the first one to buy the injectors for the LT5 from him before he specifically marketed them for our cars.

[Pete]

I thought that the injectors were RCs, but they actually came from Fuel Injector Connection. The coils are factory and were bought from the dealership.

#4 and #7 have no spark for certain. I was reading further through the FSM tonight (Chart C-4) and it seems like the diagnostic flow goes quickly to a faulty ignition module. I’m a novice (at best), but I can see where if someone wasn’t thorough they might jump to this faulty ignition module conclusion.
Thanks for the ideas you guys are providing here. There’s a lot to be looking for that could be simple and I really hope it is at this point.
Jason

Jason if you don't have spark on 4 & 7 and you already tried IM and ECM only 2 things left spark plug wire or bad coils check simple things first check plugs behind the coil packs maybe when they replaced coils they bend a pin etc.

Pete

[GOLDCYLON]

Yeap injectors,i initially wrote and guessed that you had FIC's but removed it. LOL
There have been a few ZR-1 guys on here that had FIC injector issues.

Jason don't spend another dime just borrow a set of good injectors from someone and install yourself if all is good then order new Accels

http://www.jegs.com/i/Accel/110/150821/10002/-1
All of the FBI Z's have Accels never had one issue with them and 3 of them are big inch 10 second Z's.

You saved a few bucks on injectors but spend it elsewhere and now will spend more to replace them.Penny smart dollar foolish.

FIC will warranty them the issue i have is the 2 hour labor, $75 gaskets and all the frustration is just not worth the savings for used injectors.

Pete

Why im running RCs install and forget about em. Accels are great as well. I will never/ever recommend anyones rebuilt injectors. Even if warrentied its a PITA do have to go throught it ALL over again. I agree with you 100% Pete. GC

[Fully Vetted]

Yeap injectors,i initially wrote and guessed that you had FIC's but removed it. LOL
There have been a few ZR-1 guys on here that had FIC injector issues.

Jason don't spend another dime just borrow a set of good injectors from someone and install yourself if all is good then order new Accels

http://www.jegs.com/i/Accel/110/150821/10002/-1
All of the FBI Z's have Accels never had one issue with them and 3 of them are big inch 10 second Z's.

You saved a few bucks on injectors but spend it elsewhere and now will spend more to replace them.Penny smart dollar foolish.

FIC will warranty them the issue i have is the 2 hour labor, $75 gaskets and all the frustration is just not worth the savings for used injectors.

Pete


Pete - Do you prefer the Accels over FIC's new SS injectors as well or just their rebuilt ones?

http://fuelinjectorconnection.com/shop/viewitem.php?productid=115

[scottfab]

...snip...
#4 and #7 have no spark for certain. I was reading further through the FSM tonight (Chart C-4) and it seems like the diagnostic flow goes quickly to a faulty ignition module. I’m a novice (at best), but I can see where if someone wasn’t thorough they might jump to this faulty ignition module conclusion.
Thanks for the ideas you guys are providing here. There’s a lot to be looking for that could be simple and I really hope it is at this point.
Jason

ah ha... now we have data.
As long as you see spark on any other plugs, it's time to focus
on 4 & 7. As Pete has written, wires or coil BUT we can't as of yet rule out the feed wires from the DIS to the coil. So.......

Measure the resistance between the spark boot at 4 to the spark boot at 7. Compare it to spark plug boot 2 and 3. They should be within a few K ohms (a few 1000 ohms)
If they are close you're going to have to jump into the deep end of the pool.
Here is an isolation step.
It does require pulling the plenum. If you're not comfortable doing this maybe a friend or mechanic can do it for you. Or we can guide you through it. There are threads here on the forum or you can look on the club webpage at:
http://www.zr1netregistry.com/Information/TechNet/Troubleshooting/tabid/148/articleType/ArticleView/articleId/208/categoryId/61/LT5-Plenum-Removal.aspx

Once there pull the 4/7 coil and look at the mounting pins.
Look ok? Not bent or busted off?
Fix as necessary else .....continue
Leave the coil out.
Now find the two (three wire) harnesses that plug into the DIS. These are known as connectors C3 and C4. (Note there are two other wire harnesses going to the DIS, one with many pins and one the two. You don't want these.)
You want to focus on the three wire harness called C4.
It will have these wires:
1. dark blue
2. green
3. black
Check the resistance from the drk blue one to the pins that come up to go into the 4/7 coil.
What do you get?

If any of this is not clear, ask away.
Pic added for convenience.
http://zr1.net/forum/picture.php?albumid=199&pictureid=1762

[Pete]

Pete - Do you prefer the Accels over FIC's new SS injectors as well or just their rebuilt ones?

http://fuelinjectorconnection.com/shop/viewitem.php?productid=115



These look the same as the Accels so either will work fine.

Pete

[Jason 91]

David, to answer your question, the injectors are black.

Scott, what you say above makes sense to me. I need to find the time soon to dive in and, as you say, get dirty.

Thanks guys.

Jason

[scottfab]

David, to answer your question, the injectors are black.

Scott, what you say above makes sense to me. I need to find the time soon to dive in and, as you say, get dirty.

Thanks guys.

Jason

Keep us posted. No spark is a smoking gun.

[Hib Halverson]

This thread makes great reading. The problem sounds obscure. I love **** like this. I wish the car was closer to me so I could help.

That the no-spark situation not intermittent, ie: the two wires are just flat-assed dead, is actually a good thing because it will be easier to isolate the problem.

In re: injectors...there is no such thing as a "rebuilt" injector. That's marketing BS by people who run injectors through an ASNU machine or some other ultrasonic cleaner. They scam people with the "rebuilt" term when, really, all they've done is clean them, replaced the screens and o-rings and maybe flowed them. What do I use? RC Engineering. I put them in in 1997 and never touched them again.

I'd tend to set any injector work aside right now. Since you already know there's no spark for 4 and 7, the problem is unlikely to be a fuel issue. Right now getting off into injectors is a distraction.

Next, I'd take some of ole "Scottfab's" ideas on wiring diagnosis to heart.

I've read the entire thread twice and no where do I see a statement that the existing 4-7 coil has been replaced with a known-good unit as a test. If it was done and not discussed or I missed it, I apologize for the redundant suggestion. If it's not been done, I'd try it.

My guess is this is either a bad coil, two bad plug wires (unlikely) or one of the wiring issues "Scottfab" talks about.

Good luck.

[LGAFF]

As stated in my first post, I would start with Dark Blue wire off the bottom of the DIS Circuit 932.....its the one wire that is isolated to 4-7 in the factory manual.

[scottfab]

As stated in my first post, I would start with Dark Blue wire off the bottom of the DIS Circuit 932.....its the one wire that is isolated to 4-7 in the factory manual.

As stated on my first post:
"Fortunately you can do end to end wire tests on
the harness that runs to the coil from the DIS."

But since there's no points or score keeper, eh... doesn't matter.

[Paul Workman]

Having a 90, and not wanting to muddy the water with a possible irrelevancy, I've kept to just lurking up to now. But, now I have an observation and a question:

Out of curiosity, I took direct measurements of the primary and secondary windings of a set of AC/Delco ignition coils and was surprised to see two of them read open on the secondary (spark) side.:icon_scra However, the other two read 5.682kΩ and 5.590kΩ. However, the primary resistance was .4xΩ for all 4 of them.

The thing is, I changed the coils as a matter of routine at about 35800 miles as part of a starter and ignition R&R project. Up to then the coils seemed to be working OK.

I recon I'd not put the "open" coils back in service, but curious what others may have experienced when measuring resistance across the secondary (SPARK) terminals?

Another thing...

At the risk of that irrelevancy I mentioned, my ('90 FSM) shows an individual driver circuit for each coil, mounted to the coil module. Is that also the case with 91+ coil modules? If so, then the driver for that coil needs to be considered (in turn) and we can get to that. But, first is there a dedicated driver (ganged or descrete) mounted on the coil mod?

BTW, pulling the plenum is a right of passage for a ZR-1 owner. Might as well get that one out of the way!;)

P.

[scottfab]

Paul, I believe the "solid state driver" shown (4 of them) in the FSM to
be an error. The only drivers I know of are in the DIS.

As for the "open" measurement on the coils that work try using a 10k ohm resistor in series. I suspect you DVM is not handling the inductive kick from the coil very well. Or set up 100k rheostat in series with the meter and the coil then turn the 100k down to 0k. The reading then will be the coil resistance.

[Paul Workman]

Paul, I believe the "solid state driver" shown (4 of them) in the FSM to
be an error. The only drivers I know of are in the DIS.

If that is the case (and you may well be correct) then since the DIS was swapped and there was still no spark from the 4/7 coil, I have to think wiring or a bad coil. Course we're assuming (and THAT'S never good) the replacement DIS and the coil were not faulty. But, as Dom points out, the chances of that happening...on the same 4/7 coil are maybe 'bout the same as winning the lottery!

*snip* As for the "open" measurement on the coils that work try using a 10k ohm resistor in series. I suspect you DVM is not handling the inductive kick from the coil very well. Or set up 100k rheostat in series with the meter and the coil then turn the 100k down to 0k. The reading then will be the coil resistance.

Well...not wanting to vere into an esoteric discussion, I think you were referring to current lag due to inductive reactance. However, since the core has to become saturated (or tries to) in a few mS (at 7000 rpm), certainly the inductive reactance value would have gone to practically zero in the several seconds of applying a DC voltage (from my Fluke DMM), leaving only the wire resistance (ohms) of the windings. As for inductive "KICK", it occurs when current is cut off and the magnetic field collapses (actually). (Besides, two coils read open, but the other two read OK. Reactance/kick or what ever would be the same for all 4, I would think.)

But, the coils with an "open" reading were working at the time they were removed. :confused: However, being the "open" appeared on the secondary (read: high voltage) side, it isn't too hard to imagine if there was a tiny break in the internal connection or solder joint between the winding and the spark wire post, it is conceivable the voltage would be high enough to jump the breach anyway. (The coil is firing two plugs at the same time, so what's one more gap - more or less? High voltage introduces a whole nother aspect to troubleshooting. Saw a poor Navy Firecontrol striker dude lean past an open high voltage slip ring pin fitting (that had who knows what open loop voltage was on it!) and drew an arc about 8 inches long to the side of his neck.)

Anywayz...I agree with you re the wiring/connectors. The fact that the problem didn't really crop up until the injectors were replaced...by some mechanic...makes me wanna say HMMMmmmmm....[-X

P.

[scottfab]

If that is the case (and you may well be correct) then since the DIS was swapped and there was still no spark from the 4/7 coil, I have to think wiring or a bad coil. Course we're assuming (and THAT'S never good) the replacement DIS and the coil were not faulty. But, as Dom points out, the chances of that happening...on the same 4/7 coil are maybe 'bout the same as winning the lottery!

Agreed, very unlikely another bad DIS but to be kept in the back of our collective minds. And as for the missing "solid state drivers" shown on the FSM we'll have to wait for someone to find them :-D


Well...not wanting to vere into an esoteric discussion, I think you were referring to current lag due to inductive reactance. However, since the core has to become saturated (or tries to) in a few mS (at 7000 rpm), certainly the inductive reactance value would have gone to practically zero in the several seconds of applying a DC voltage (from my Fluke DMM), leaving only the wire resistance (ohms) of the windings. As for inductive "KICK", it occurs when current is cut off and the magnetic field collapses (actually). (Besides, two coils read open, but the other two read OK. Reactance/kick or what ever would be the same for all 4, I would think.)

I'm thinking the other way. The instantaneous current required by the DVM's constant current source (ohms range) can get confused. (lockup) I've seen it happen having evaluated competitors DVMs to Tektronix DVMs.
The range locks up and gives unexpected results. However, if you measured consistent "open" on a coil then ???? could be you theory bellow. In any case using a reasonable resistive value in series eliminates this.
The early HPs were bad for this. Long story of how I know this.

But, the coils with an "open" reading were working at the time they were removed. :confused: However, being the "open" appeared on the secondary (read: high voltage) side, it isn't too hard to imagine if there was a tiny break in the internal connection or solder joint between the winding and the spark wire post, it is conceivable the voltage would be high enough to jump the breach anyway. (The coil is firing two plugs at the same time, so what's one more gap - more or less?

I've never seen this but, very plausible.

High voltage introduces a whole nother aspect to troubleshooting. Saw a poor Navy Firecontrol striker dude lean past an open high voltage slip ring pin fitting (that had who knows what open loop voltage was on it!) and drew an arc about 8 inches long to the side of his neck.)

Ouch. not good.
I've been zapped hard a few times in my career, once by the HV section of a large screen CRT that just happened to be voltage regulated. It felt ME as a load and simply provide the necessary current to maintain it's V. I think I flew in the air a waz. Maybe 5ft.

Anywayz...I agree with you re the wiring/connectors. The fact that the problem didn't really crop up until the injectors were replaced...by some mechanic...makes me wanna say HMMMmmmmm....[-X

P.

My best guess at this point is the connector at the input of the coil. Bent of broken pin.

Someone needs to go over and help get an answer. The suspense is sure there.:confused: