|
|
|
Your donations help keep this valuable resource free and growing. Thank you.
|
Cross Firing |
Post Reply 
|
Page <12 |
| Author | |
purple72Gremlin 
AMC Addicted 
Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16614 |
 Post Options
 Thanks(0)
 Quote Reply
 Posted: Aug/15/2018 at 10:26pm |
|
5 and 7 will crossfire due to the firing order..... if it coughs and backfires.....makes me think a valve train problem....bent pushrod, cam going flat .. or timing too retarded.
|
|
 |
|
|
jesse
AMC Nut
Joined: Feb/22/2010 Location: Edinburg, Texas Status: Offline Points: 299 |
Post Options
Thanks(0)
Quote Reply
Posted: Aug/16/2018 at 10:39am |
|
So here is what I did yesterday evening. Pulled all plugs and brushed them clean (Plug on # 8 had a piece of carbon stuck in-between insulator tip and side electrode), re-routed wires 5 and 7 so that they not run parallel. Took her out for a drive and the issue is gone. So on second gear I went up to 3,000 RPM then gradually stepped on it with no hesitation or pop.
Edited by jesse - Aug/16/2018 at 11:19am |
|
|
|
|
one bad rambler
AMC Addicted
Joined: Jan/09/2008 Location: On The Island Status: Offline Points: 2007 |
Post Options
Thanks(0)
Quote Reply
Posted: Aug/16/2018 at 8:39pm |
|
You can check cross firing with a timing light.Just move it from cyl to cyl and you will see the increase in flashes
|
|
 68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
|
|
|
|
|
ccowx
AMC Addicted
Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510 |
Post Options
Thanks(0)
Quote Reply
Posted: Aug/17/2018 at 9:21am |
|
Couple of things.
I chased this kind of thing on my car a while back. I thought it could not be wires because they were brand new Bosch wires. New wires can be defective these days, so it could still be them. If you had leakage, even with the wires parrallel, then you have bad wires. I replaced mine with Pertronix wires had no further problem, even when loomed parrallel. If they leak like that, they will probably get worse and could start jumping-grounding out to the block or something else. RE-routing them is a nice dignostic fix, but leaking wires are not good and are a performance issue and also a potential fire hazard! I would also consider bumping the timing a degree or two. 32 total sounds a bit light, so unless you have tried and it can not take any more, you will probably find it works better with a bit more timing. Chris
|
|
|
|
|
jesse
AMC Nut
Joined: Feb/22/2010 Location: Edinburg, Texas Status: Offline Points: 299 |
Post Options
Thanks(0)
Quote Reply
Posted: Aug/17/2018 at 3:39pm |
|
I will definitely look into that CCOWX...thanks!!
|
|
|
|
|
billd
Moderator Group 
Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
Post Options
Thanks(0)
Quote Reply
Posted: Aug/17/2018 at 6:41pm |
|
Never run plug wires neatly - don't run them parallel. Even those next to each other in the firing order as you can introduce a spark at the wrong time and not know it.
It's called induction - where the magnetic field surrounding one conductor crosses the other conductor and when the field collapses it induces a spark on that second conductor. 1-8-4-3-6-5-7-2 You can see 5 and 7 sit next to each other in the firing order and physically - so if there's "cross-fire" you would be more likely to notice it, but that doesn't mean two other wires running parallel one isn't inducing a spark in the neighbor wire - it just won't pop. There's a reason the factory doesn't make plug wires look like a show car - it makes me realize so few know very much about auto electric systems when I see all of the wires perfectly spaced like train track rails, all nice and tidy in perfectly straight lines right next to each other. If the wires CROSS each other somewhere, you can get rid of true cross-fire. It's nothing to do with insulation so new wires won't help if you run them the same exact way as the old ones. Now if there is an insulation break-down, that's a different matter - that's where a spark jumps through to another wire. But cross-fire due to induction won't change a bit with new wires - although some swear it will - but those folks made some OTHER change in the wire routing when they replaced them and said see, the new wires fixed it. No, your routing fixed it. Again, it's possible to have sparks jump, but the induction situation is more common than you think. And a backfire can be due to LEAN - bad accel pump, lean situation, plugged off-idle circuit, and so on. So be SURE of your situation before tossing parts at it.
Anyway, I NEVER run wires parallel - the factory didn't, and to do so is ignoring physics. It may look pretty, but it's an invite to trouble. When I did the Plymouth troubleshooting contest, you got DOCKED for improper wire routing and those who made the plug wires look pretty generally got docked. |
|
|
|
|
MacGyver
AMC Apprentice 
Joined: Jul/10/2018 Location: Ontario, Canada Status: Offline Points: 182 |
Post Options
Thanks(0)
Quote Reply
Posted: Oct/13/2018 at 8:27pm |
|
Bill, you wouldn't happen to have a pic of your messy but practical wiring, would you??
 I just went through this exact situation! Under load the car would misfire like crazy!! I re-routed 5 and 7 to make sure they were nowhere near each other, and it made a huge difference!! But as the engine got hot, the misfire would come back but not as bad as before... I wondered if the 20 year old wires could be an issue? Lol!! So I re-routed every single wire to come nowhere near any other, using some very creative looming with a lot of zip ties to coolant hoses, vacuum lines and anything else non-metallic!! Problem gone!!! So today, figuring the car is probably due for a new set of wires, I finally installed a new set!! It's REALLY difficult to run the wires so that they don't touch each other or run parallel!! Especially at the distributor! You said the factory didn't do it, but there are those loom things on the rocker covers that would do exactly that!! Looking for some sort of guide to looming!! 
|
|
|
|
|
FSJunkie
AMC Addicted
Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
Post Options
Thanks(0)
Quote Reply
Posted: Oct/14/2018 at 3:54am |
|
The factory absolutely routed the wires in an organized manner. They went through the trouble of having 4-wire loom holders on top of each valve cover and another one on a bracket behind the coil. They basically ran a bundle of four parallel wires to each cylinder bank and the wires were parallel to each other over most of their length. They didn't crossfire because the wires were suppressor-type wires with spiral conductor cores that greatly reduce electromagnetic transconductance. They also only had 8 to 25 kilovolts running through them. The problem is cheap wires, bad wires, or high performance wires. Cheap wires don't have suppressor cores. They are solid conductors...literally just straight strands of wire and so are high performance wires. High performance wires are not always your friend. Old suppressor core wires can get damaged inside and form sections that now work like a straight conductor or get breaks in them that arc over and that causes all kinds of heck. Any of them can crossfire, especially when subjected to the higher voltages created by wider plug gaps and hotter coils. They also turn your AM radio into an auditory tachometer. Good quality suppressor-type wires in good condition will not crossfire, even at higher than standard voltages. My Buick V6 has an OE HEI with an OE spec plug gap of .060". It fires at 15 to 40 kilovolts. The OE wires were 8mm suppressor wires run in parallel. I have 8mm silicone suppressor wires run in parallel on it right now and it doesn't crossfire even if I pull the plug boots from the plugs to spike the firing voltage. I'm not talking out my backside either. I watch all six cylinders on an ignition scope while I'm doing this. I'd see crossfiring if it were happening.
Edited by FSJunkie - Oct/14/2018 at 3:57am |
|
|
1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
|
|
|
|
Steve_P
AMC Addicted
Charter Member Joined: Jun/28/2007 Status: Offline Points: 3809 |
Post Options
Thanks(0)
Quote Reply
Posted: Oct/15/2018 at 8:57am |
Read George W's post. He is correct on the routing sequence.
|
|
|
|
|
MacGyver
AMC Apprentice
Joined: Jul/10/2018 Location: Ontario, Canada Status: Offline Points: 182 |
Post Options
Thanks(0)
Quote Reply
Posted: Oct/22/2018 at 7:25pm |
|
Thanks for the input, FS!! Good info!!
Steve: Somehow I managed to miss George W's post! Whoops!! Also great info!! And I actually loomed the driver's side that exact way!! It just seemed to work out best with the wire lengths I was working with and keeping 5 and 7 apart!! They were "middle of the road" quality suppressor wires... Problem gone!! So far!! 
|
|
|
You Drive A What?!?
|
|
|
|
|
Post Reply
|
Page <12 |
Tweet
|
| Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |
Click for TheAMCForum Rules
Topic Options
FSJunkie wrote: