TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - Cross Firing
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Cross Firing

 Post Reply Post Reply Page  12>
Author
Message
jesse View Drop Down
AMC Nut
AMC Nut
Avatar

Joined: Feb/22/2010
Location: Edinburg, Texas
Status: Offline
Points: 279
Post Options Post Options   Thanks (0) Thanks(0)   Quote jesse Quote  Post ReplyReply Direct Link To This Post Topic: Cross Firing
    Posted: Aug/15/2018 at 11:40am
Did a google search with no luck. Are AMC V8's known for having cross fire issues on a particular area? I read that Ford engines had this problem between wire # 7 and #8 with a solution of putting wire #6 in-between to prevent cross fire. Having an issue with cough/backfire through carburetor on my 390.
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Online
Points: 3499
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 11:50am
Guess maybe #5 & #7 maybe, back end, driver's side, since they fire in sequence,
and those two wires are very easy to get mixed up and connected wrong / crossed.
1-8-4-3-6-5-7-2
Back to Top
White70JavelinSST View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/08/2012
Location: Minnesota
Status: Offline
Points: 3226
Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 2:50pm
I'd say crossfire on the AMC V8 is more susceptible when using cheap wires or old cracked wires.

I haven't ever experienced it with over 135K miles of driving. But I ditched the factory wires early on, and installed Blue Max wires way back when.

Now the car has MSD wires, routed neatly side by side and no issues.
70 Javelin SST, second owner, purchased 1972
Back to Top
Midnight Rambler View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/17/2011
Location: SoCT
Status: Offline
Points: 1253
Post Options Post Options   Thanks (0) Thanks(0)   Quote Midnight Rambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 4:19pm
If you don't have a great set of wires now, replacing them with a new set of well insulated wires isn't exactly throwing parts at a problem either.

'66 American 440 Convertible 290/WC M-37/AMC 20 3.15
'97 Jeep Wrangler 4.0 5sp
Back to Top
White70JavelinSST View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/08/2012
Location: Minnesota
Status: Offline
Points: 3226
Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 5:11pm
The best way I've found to determine if wires are cross firing is to open the hood in the dark and watch the wires for arcing between them.

That way you don't have to through parts at it in hopes of fixing it.....

That's how I solved the miss firing issue on an old Chev wagon I had.

If that doesn't do it the next thing is check the inside of the distributor cap for carbon tracking between posts.
70 Javelin SST, second owner, purchased 1972
Back to Top
jesse View Drop Down
AMC Nut
AMC Nut
Avatar

Joined: Feb/22/2010
Location: Edinburg, Texas
Status: Offline
Points: 279
Post Options Post Options   Thanks (0) Thanks(0)   Quote jesse Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 5:12pm
PerTronix Ignitor, PerTronix Flame Thrower Coil and Accel 8mm wires all were installed a few months back. The 390 is backed by the M12 Borg Warner. On second gear and at around 3500 RPM the engine starts to hesitate and as I hit the throttle some more...POP!

Edited by jesse - Aug/15/2018 at 5:15pm
Back to Top
White70JavelinSST View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/08/2012
Location: Minnesota
Status: Offline
Points: 3226
Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 5:18pm
Timing specs please?

advance mechanism functions correctly,      right?

accelerator pump works,     correct?


70 Javelin SST, second owner, purchased 1972
Back to Top
jesse View Drop Down
AMC Nut
AMC Nut
Avatar

Joined: Feb/22/2010
Location: Edinburg, Texas
Status: Offline
Points: 279
Post Options Post Options   Thanks (0) Thanks(0)   Quote jesse Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 5:45pm
Initial timing is set at 12* advanced and total timing at 32. Accelerator functioning properly from what I can see. The carb is a 750 Edelbrock and the arm link is set to the very bottom hole on the accelerator pump. Going to plug the vacuum advance and run the car and see what it does.
Back to Top
george w View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Jan/27/2013
Location: New Jersey
Status: Offline
Points: 1523
Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 9:38pm
There is a particular factory order for putting the spark plug wires in the separators mounted on the valve covers.
Passenger side bank: wires for cylinders 2,4,6,8 go in order from front to back. wires for drivers side bank for cylinders 1,3,5,7 go in this order from front to back: front most position, Cylinder 1, second position, Cylinder 5, third position, Cylinder 7, Rear most position, Cylinder 3.
If you want to see the order for the intermediate separators them PM me your email and I can send you pictures of everything.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
Back to Top
Trader View Drop Down
AMC Nut
AMC Nut


Joined: May/15/2018
Location: North America
Status: Offline
Points: 393
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/15/2018 at 10:34pm
If firing order is correct, then cross-fire is a function of poor insulation or parallel running of ignition wires in most cases.
Non conductive spacers or running wires at 90° to each other will eliminate the problem.
Start at the distributor and look for parallel running wires, reroute or space.
As mentioned above, good wires are also a must. 
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.078 seconds.
All content of this site Copyright © 2012 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or