04 zf6 fuel knock

mamumtsllc

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Sep 4, 2014
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Hey guys. Got a 04.5 lly 3500 with the zf6 manual trans. Came in for fuel knock/miss and excessive black smoke. So ran cylinder cut out and found #6 had the knock. Kill the cylinder it goes away. Balance rate was a +8. Every other cylinder was +/- 3-4. So figured there's the problem. Changed #6 injector, cranked it up and exactly the same. So I thought maybe #5 which is directly across. So we put #6 injector in #5 hole. No change. Pulled ficm off good running truck. No change. Put #5 injector in #3 since that's the next cylinder in firing order thinking maybe??? No change.

So I'm back to the forums where you can actually get real help. No blow by. But im lost. Looking for ideas or any other wild ghosts to chase. Thanks


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2004LB7

Well-known member
Dec 15, 2010
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Are you using the Tech 2 or another tool? Some others can read the injector numbers wrong. EfiLive has been known for this issue.

Some speculate that the number is actually the firing number and not cylinder number. So #6 firing would be #5 cylinder

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mamumtsllc

Member
Sep 4, 2014
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Are you using the Tech 2 or another tool? Some others can read the injector numbers wrong. EfiLive has been known for this issue.

Some speculate that the number is actually the firing number and not cylinder number. So #6 firing would be #5 cylinder

View attachment 116358
Using a snap on Solus scan tool. I believe it actually kills the cylinder number that you select from my experience. But I will definitely pay closer attention to that tomorrow. Sounds like it's coming from the driver side.

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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On a customers vehicle, you should be running a compression test next. You assume injector when it could very well be something else. Also you never posted main injection rate for the balance rates. Without it, you only have half the story.
 

mamumtsllc

Member
Sep 4, 2014
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On a customers vehicle, you should be running a compression test next. You assume injector when it could very well be something else. Also you never posted main injection rate for the balance rates. Without it, you only have half the story.
Compression test is next in line. But let me just throw this out there to make sure I'm not missing anything. No blow by. Zero. So that tells me the cylinder walls and rings are still intact rite? No noise in intake or exhaust to give me a feeling that it has a bent, burnt or broke valve. I'm more than willing to run the test but I feel that I'm not going to find a low cylinder. Am I missing something else?

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mamumtsllc

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Sep 4, 2014
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Bringing this back up from the dead. Looks like o own the truck now. I ran compression test before and want to say it was in the 350 psi range but I cannot gurantee that. So I plan to get it running to pull balance rates again and then Check compression. I've seen guys say check it hot vs cold. Which gives me the best reading? Or do both?

Thanks.

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mamumtsllc

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Sep 4, 2014
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I got a new set of batteries for this rig last week. Plan to pull it bavk up to the shop. Thinking ahead could it have a broke crank? Causing the fuel knock and black smoke? Other than those it runs smooth and does my make any noises.

I'm going to probably do a little digging but then try to move it along. Wife and kids are wanting a pontoon. So that money would do me more good towards a boat.

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clrussell

pro-procrastinator
Sep 23, 2013
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Thoughts

Have you ice picked the connectors? Any injector circuit codes?