Injector or Return line leak?

dmj291

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So i've had knock for a little while that's starting to drive me crazy.... I think it's injector related, but i'm not 100%. In an attempt to root cause the problem back to an injector, I cracked each injector line.... except #1 cyl, because the nut on the steel line wouldn't budge without possibly bending the steel lines... I've sprayed with PB blaster & will try it again tomorrow.

Just to note: Previous owner claimed to have replaced the IP & injectors (would have been within the last 20k miles)... & i'm assuming if you go through all that fuss you replace the return lines as well). One other thing to note, the truck turns over everytime without issue (leads me to believe air is not getting into the fuel system).

Here's a video of the sound.... it's an inconsistent noise (@0:18 the knock is almost gone, but at 0:25 its back and loud again)
https://www.youtube.com/watch?v=lpvfeRUkO6A

Any tips on what to look into? My thoughts are it's the #1 injector or return lines.
 

mbolton1990

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I'm not real knowledgable on these so wait for someone more experienced than me, but if I had to guess that sounds like a bad lifter.
 

icanfixall

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Its not air thats for sure. My suspicions are a bad injector. Not this does not rule out a lifter but.. Usually both a lifter or bad injector will be a constant noise. Yours definitely comes and goes. I do not feel its a bad valve hitting a piston either or a piston pin or a piston knocking the cylinders because its a loose fit in the cylinder. Not a rod or main bearing either.
 

Cruiseomatic

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Its not air thats for sure. My suspicions are a bad injector. Not this does not rule out a lifter but.. Usually both a lifter or bad injector will be a constant noise. Yours definitely comes and goes. I do not feel its a bad valve hitting a piston either or a piston pin or a piston knocking the cylinders because its a loose fit in the cylinder. Not a rod or main bearing either.

Wouldn't a rod or wrist pin knock have a more "thud" type knock?
 

dmj291

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Well... I cracked the #1 injector & that did not get rid of the sound.... although I now have a little bit of fuel leaking out of that injector or line.

I failed to mention in the first post the sound pretty much goes away once the truck is warm. Here's what is sounds like after about 10 minutes of driving.

https://www.youtube.com/watch?v=--DABPbuxNI
 
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