Ram running rough, A techs only!!
Champion
Joined: Feb 2005
Posts: 3,710
Likes: 2
From: Skagit County, WA
Ok I don't want to insult you, but maybe it's so obvious that it's been overlooked - have you double-checked the firing order?
If there is spark on all 8, and fuel to all 8, but only 4 are making an explosion, there's either a compression/leakdown or a timing (injection or spark) issue.
Have you done a leakdown test? I know you've got good compression, but these motors are known for cracking between the valves. Typically it's not a big problem though.
I had a 5.9 Dakota that the dealer fixed the plenum gasket under warranty, then I fixed it again about 10k miles later with the Hughes kit because it failed. After I sold it, the new owner didn't take care of a leaky exhaust gasket and wound up blowing the head gasket at about 100k. When I pulled the heads off, 6 of the 8 cylinders had cracks between the valves.
If there is spark on all 8, and fuel to all 8, but only 4 are making an explosion, there's either a compression/leakdown or a timing (injection or spark) issue.
Have you done a leakdown test? I know you've got good compression, but these motors are known for cracking between the valves. Typically it's not a big problem though.
I had a 5.9 Dakota that the dealer fixed the plenum gasket under warranty, then I fixed it again about 10k miles later with the Hughes kit because it failed. After I sold it, the new owner didn't take care of a leaky exhaust gasket and wound up blowing the head gasket at about 100k. When I pulled the heads off, 6 of the 8 cylinders had cracks between the valves.
Amateur
Joined: Dec 2012
Posts: 40
Likes: 0
From: las vegas
you seems swapped out everything to exclude the problem, do the basic thing, check firing order of each plug wire, and make sure every injector connector has pulse. that is all. i am not an A tech but also ase certified in engine performance and electronics for 15years.
Thread Starter
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Registered User
Joined: Dec 2012
Posts: 9
Likes: 0
you seems swapped out everything to exclude the problem, do the basic thing, check firing order of each plug wire, and make sure every injector connector has pulse. that is all. i am not an A tech but also ase certified in engine performance and electronics for 15years.
Administrator
Joined: Apr 2010
Posts: 87,397
Likes: 4,213
From: Clayton MI
No, it doesn't. You apparently have everything you should..... so, why no fire? I almost think it's time for an O-scope, and see what things look like. (spark energy, and injector pulse....)
Amateur
Joined: Dec 2012
Posts: 40
Likes: 0
From: las vegas
a good/smooth runing engine must has compression, spark, fuel, and timing. you got everything. don't trust thoes ignition caps, i seen one go bad for gm V8 new. just do the double check on firing order and swap with a new cap, it happens.
Grand Champion
Joined: Apr 2010
Posts: 5,011
Likes: 6
From: Meeker, CO
It's never too early to haul out the o-scope to check waveforms and synchronization.
Professional
Joined: Nov 2012
Posts: 165
Likes: 0
From: ledyard, CT
im not a certifided tech or whatever but if ur injectors are working and you got spark... and no fire ... i would think your intake valves on those cylinders arnt opening, they probly have good springs but bad push rods lifters or worn cam... just my thought
Last edited by Timothy Watrous; Dec 15, 2012 at 06:45 PM.