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Discussion Starter · #1 ·
So I have no spark on cylinders 5 and 10. The other 8 seem to run just fine. Car feels anemic of course only being a V8 with a couple of dead weight pistons to move.
Found a bad plug wire on 5 with damaged insulation around it like it had rubbed and been cut through over time. Thought problem solved. Not so much.
Checked the B+ and ground pins coming into the 4 post coil pack. Of course the pin that is for the other coil (not the one that feeds cylinders 5 and 10) checked out fine. The pin that feeds 5 and 10 is not providing ground meaning that coil in the 4 post pack isn't getting power. I traced that pin back to the ICM plug on the harness. I have continuity throughout. I opened up the ICM to look for blown capacitors or something I could fix (I've soldered in new capactiors on the computers in my Stealth Turbo and a BMW 540i I used to have) and found the ICM had water damage in it. So I thought bingo-blammo it's the ICM. I bought an ICM from 99RT10&GTS. He shipped it very quickly, great guy. Popped it in with great excitement...same problem. What are the odds that both ICM's would have the same bad driver. I peaked in the ICM he sent me...no water damage -- looked good inside. He's sending me another one on the chance that both ICM's had the same bad coil driver. Seems unlikely but my fingers are crossed.

I've been poking around in the FSM for the Viper and the Ram V10 for some hint of what might be going on.
In the wiring diagrams, I don't see anything further back I should trace than the K17 wire I already traced and found continuity in.

The first two images are from the Viper FSM. The last one is from the 1995 Ram V10 FSM. The RAM service manual says that the ICM and PCM work together to handle cylinders 5 and 10 (the Viper manual has no information on the subject one way or the other). Makes me wonder if, in spite of the bad looking internals of my ICM that my fine looking PCM is the problem. (I looked in the PCM, it looks good as far as I can see). Neither one is really easy to see what is going on as Dodge potted the circuit boards (covered them in resin).

Any sage advice would be appreciated. PCM, ICM...what do you thin?



RAM V10 ICM information:
 

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I think that the '96 models have the same tower arrangement as the Gen 1s. Between your attachment and mine, you will see that #5 and #10 are directly across from one another and as you confirmed, get the same ignition signal. You might have a bad 4-pole coil. The DRB-III can test coil pairs for output, along with individual injectors. One of the bad features of the Gen 1 was the siamesed PCM(SBEC)/ICM. That was fixed wtih the all-new JTEC in '96 which had enough drivers on the board to handle 10 cylinders.
96 coil pack top towers.jpg
 
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Discussion Starter · #3 ·
I'm thinking it's upstream of the coil. I replaced the 4 post coil with a used one prior to a lot of my investigation.
I think that the '96 models have the same tower arrangement as the Gen 1s. Between your attachment and mine, you will see that #5 and #10 are directly across from one another and as you confirmed, get the same ignition signal. You might have a bad 4-pole coil. The DRB-III can test coil pairs for output, along with individual injectors. One of the bad features of the Gen 1 was the siamesed PCM(SBEC)/ICM. That was fixed wtih the all-new JTEC in '96 which had enough drivers on the board to handle 10 cylinders. View attachment 150427
I think that the '96 models have the same tower arrangement as the Gen 1s. Between your attachment and mine, you will see that #5 and #10 are directly across from one another and as you confirmed, get the same ignition signal. You might have a bad 4-pole coil. The DRB-III can test coil pairs for output, along with individual injectors. One of the bad features of the Gen 1 was the siamesed PCM(SBEC)/ICM. That was fixed wtih the all-new JTEC in '96 which had enough drivers on the board to handle 10 cylinders. View attachment 150427
I replaced the 4 post coil with a used one prior to finding the bad plug wire. The coil pack was my first guess then I felt like an idiot when I replaced it and checked the plug wire and was like ohh that's a stupid easy fix. Sadly it wasn't the case. I'm still thinking the problem is further upstream. At the harness connector for the 4 post coil I get the current from battery positive to the pin feeding ground for the other coil on the 4 post pack but not this one. As the pin feeding the other cool in the same pack does what it seems like it should (fluctuating voltage on an analog multimeter when running) and the pin feeding 5 and 10 seems dead when runnjng I believe the problem is upriver. So it does sound like you confirmed there is some level of ibterrdependace between the ICM and Ecm on my 95.i appreciate it. I also appreciate that you took time to take a photo of your coil pack.
 

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I dug up my '93 manual and the plug wire layout is different than my GTS.
20210319_223658_resized.jpg 20210319_222743.jpg 20210319_225045_resized.jpg 20210319_225953_resized.jpg
 

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Discussion Starter · #5 ·
Anyone know which cylinders the coil drivers in the ECM vs ICM are responsible for in a 1995?
The ground is not cylcing on and off for the cylinder 5/10 coil at the harness connection. There is continuity back to the ICM so I assume that one is controlled by the ICM.
I have my fingers crossed that this second ICM will do the trick though with each try of the same thing I'm starting to remind myself of that Einstein quote everybody loves. Good thing I'm no Einstein.
 

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I am 96% certain that all Gen 1s use the same electronics for ignition and injector control. The first attachment says ICM fires all coils and injectors 1&5. Have you tried looking at your Blinky Codes on the Message center?
 

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can you bench test the coils? I've done that with coil over plugs before but not coil packs.

Plus can you send me the RAM V10 doc? I always like having and reading tech doc to cross reference stuff. Plus I can put it in front of my porn mags when I'm reading the articles.
 

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Discussion Starter · #8 ·
can you bench test the coils? I've done that with coil over plugs before but not coil packs.

Plus can you send me the RAM V10 doc? I always like having and reading tech doc to cross reference stuff. Plus I can put it in front of my porn mags when I'm reading the articles.
I bench tested it. All of the resistance values are in spec for the primary and secondary on each coil according to the procedure for the FSM.
It has to be a power transistor or a coil driver or something like that as the ground does not flicker on and off on one of the 3 pins on the wiring harness that runs to the coil. So it's definitely upstream from the coil. The other ground pin will flicker on and off like it should causing the voltage to fluctuate on my multi-meter.
But just because it's upstream from the coil doesn't mean I know what it is. The ICM had water in it so that was my first guess. That's looking less likely by the day though.

Also check your PMs for the Ram V10 information you asked for.
 

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Discussion Starter · #9 ·
I am 96% certain that all Gen 1s use the same electronics for ignition and injector control. The first attachment says ICM fires all coils and injectors 1&5. Have you tried looking at your Blinky Codes on the Message center?
Yeah, I pulled the codes right after getting the Viper. I'm down to two codes: single/multiple misfire and low voltage on the evap solenoid circuit. That misfire code is what had me hunting through looking for spark as it is easier than the injectors. I cleaned my injectors and used one of those little rebuild kits on my Stealth Turbo. It was enjoyable but not something I wanted to do until I got the spark situation straightened out. I also had to replace a bad coil on that. That Stealth coil created a ground fault and a fuse that ran like a million things kept blowing. Either way, I love that car it's a joy to drive. That got off topic fast.
 

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I meant to bench test by applying 12V to it through a plug wire into a plug and see the color and intensity of the spark created.
 

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Discussion Starter · #11 ·
Great idea. No I haven't. I didn't even realize that was a thing. Thanks for clearing that up for me.
I meant to bench test by applying 12V to it through a plug wire into a plug and see the color and intensity of the spark created.
 

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Discussion Starter · #12 ·
I meant to bench test by applying 12V to it through a plug wire into a plug and see the color and intensity of the spark created.
I got it figured out. Even though the wire from pin 1 on the ICM harness had continuity, the terminal on that the ICM pin would go into was recessed by maybe a third of an inch on the harness. Popped open the harness, re-seated the terminal and it ran on 10 cylinders with a new to me known good ICM. Switched in my old ICM and it fires on all 10 cylinders. So it was a wiring harness issue for anyone who was curious.
 

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Thanks for sharing the final outcome. Now go have fun!
 

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Discussion Starter · #14 ·
Thanks for sharing the final outcome. Now go have fun!
I sure will.
I should have worn my brown pants when driving it.
I know stock power is pretty mild for a lot of you guys, but it's my first experience with a Viper running an all 10 cylinders.
That combined with old, hard rear tires.
Fun. Scary fun. A smile was combined with an ohh crap feeling as the tail slid out in first.
So I tried it in second which was another oohhh crap tail sliding out experience but at a higher speed.
I'll need to learn to roll into the throttle. None of that Turbo V6 mashing on the throttle that I like to do in the Stealth.
 

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GET NEW RUBBER NOW!!!
 

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Glad you got it worked out, I still think you should keep my box as a spare :), but good to hear is was an "easy" fix
 
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