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Discussion Starter #1
Hey everyone,

Trucks been running fine for months! So I haven't been on here much... funny how that is :)

Just last night my truck took about 1/2 sec. longer to crank than normal... seemed to idle a little rough. Then about 1/4 mile home doing about 30 mph there was about 5 hard knocks and stuttering loss of power then right back to normal.

Once home (about another 1/4 mile) it idled okay but with hazy smoke.

This morning I needed to move it to get my wife's car out and I noticed what looks like a blow by stain on the driveway. Started the truck up just fine and while backing it down the street 20 yds or so the 5 knocks, stuttering and heavy smoke. It cleared up after I put it in FWD to angle in to park.

I think my signature isn't showing here but it's an '05 w/ automatic. Engine rebuilt about 70K ago and that's about how old the injectors are. I replaced one due to another issue about a year ago.

I've read many pages of posts and best I can tell is that I've caught the early start of a bad injector / injector knock.

Found this video:

Very much like what mine sounded like but for only a few knocks.

I'm sure I'm due for injectors (about 50K right?) so I'm just getting your opinion on this before I dive more into it. I drive a lot locally w/ this truck so is this a "park it and don't drive it 'till fixed" situation or do you think I have time to run some 2SO in it and see if that clears up?

Hey, thank you very much for any help you can provide... I know this topic is popular and folks probably get tired of dealing with it but us shade tree mech's need a little guidance :) THANKS!
 

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Discussion Starter #2
Definitely not making oil... oil level at least right now is right on. Doing the oil-drop-on-paper-towel-test right now.


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I would try some ATF. I developed a little stumble a few years ago threw in some ATF and cleared it right up. You'll have to search to see which kind. I recall there was a specific type you do/don't want to use.
 

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Discussion Starter #4
I would try some ATF. I developed a little stumble a few years ago threw in some ATF and cleared it right up. You'll have to search to see which kind. I recall there was a specific type you do/don't want to use.
Thank you!!!


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Discussion Starter #5

So... filled fuel filter bowl with ATF... cranked... let it sit 30min... started it up... no real improvement, maybe optimistically slightly better.

I saw a lot of smoke under hood. Looked under the truck and there really wasn’t any noticeable blow-by. But it was raining fuel.

I’m thinking another contributing factor could be leaky fuel line connectors on maybe 3 injectors. I caught sight of a drip at the connector at the crossover tube on either #4 or #5.

Could loss of fuel / fuel pressure cause these injectors to knock?


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Put it in reverse and see if you have rpm hang (injector hang). Wouldn't hurt to put in 2QT of ATF DEX/MERC and a QT of WallyWorld TCW3 in fuel tank. Do you have add fuel filtration? Worth the investment.
 

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Discussion Starter #7
Thank you!

Question: does the injector knock cause increased chamber pressures on both strokes leading to the leaks at the fuel lines where they connect to the crossover tubes?

Or....

Does the fuel leak cause the injector knock?

Or...

None of the above, buy new injectors, tubes and lines, don’t pass go do not collect $2000 ;)

Thanks!!!


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The injector hard lines are known to crack on either #4 or #5, I don’t remember which one. A quick search should be able to tell you very quickly which one is more common.

Yes, fuel pressure fluctuations can cause injector knock.
 

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Try going through and torque all your feed tube.

Injector line 4 is the one that's prone to cracking. Make sure the bracket that holds that line is not loose.
 
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# 4 is the usual culprit.
ATF in the fuel filter housing will get you no results, it needs to go through with the fuel.
1qt Dex/merc ATF and 1 qt TCW3 2 stroke oil is the usual treatment with a full tank, then a second time.
 

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Discussion Starter #11
The injector hard lines are known to crack on either #4 or #5, I don’t remember which one. A quick search should be able to tell you very quickly which one is more common.

Yes, fuel pressure fluctuations can cause injector knock.
Thank you! This will help me narrow things a little first before buying a whole injectors kit


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If the hold down for the injector line is loose, like the #4 that usually fails, it almost sounds like a knock and is loud enough to be heard in cab over a 5" exhaust.
 
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Discussion Starter #13
If the hold down for the injector line is loose, like the #4 that usually fails, it almost sounds like a knock and is loud enough to be heard in cab over a 5" exhaust.
nosympathy, thank you very much... I'm hoping that's it... it knocks and shutters/shakes pretty hard and a lot of fuel dripping down the back of the engine.

I'm planning on doing another visual test soon where I can have someone else start the truck while I watch inside the engine compartment. Last time the smoke got going so much inside the compartment I couldn't see. There is a decent amount of fuel leaking out of the tube(s) causing this smoke. So my previous comment about blow by was an assumption based on the fuel stain on the driveway... it's possible now that was just leaked fuel.
 

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Maybe pull the valve cover, toss an old towel over the length of the head, have someone fire it up and see if there is any fuel spraying onto the towel. Might help narrow things down if its under the valve cover. Last thing you want is to get hit by 5~7k psi fuel... There is a return line on the back of the head (IIRC, never had to mess with it), not sure how that is setup but should be looked at.

If you have a knock, that is a stuck or leaky injector. It is possible one injector is stuck and the pressure is blowing out internally taking the path of least resistance
 

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Discussion Starter #15
Okay, I can confirm now there’s a jet blast of fuel spraying out under the #4 injector fuel/feed line.

Relatively speaking that could be good news... I can get an upgraded replacement line locally tonight!

I plan on swapping that out and testing. I’ll post back up my results later.


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Discussion Starter #16

There it is... just about 1/2” up from the fitting is a crack along the length of the tube. Installing new line now...


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Discussion Starter #17
Found these torque specs on here somewhere for the injector fuel / feed lines:

“Crossover tube nuts 37 ft-lbs

Injector line at the head 22 ft-lbs

Injector line at the rail 27 ft-lbs”

Couldn’t get a torque wrench back in there no way no how.

So I consulted my German service manual and snugged them down “guttenteit”.


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That is the feed line that has been known to rupture.... There is a way to get the torque done right, I suggest you find the way. The way I did it was to drop it off & let a pro do it lol. (no place to work on it)
 

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Get a crows foot to torque the feed tubes.
 

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I replaced mine about 20k miles ago on the side of the road. I didn’t torque it. I haven’t had any issues. I’ve also done probably a 100 of these on large diesels and never torqued a single one. I’ve never had an issue with a single one. Make sure they seat properly and get them good and tight, there won’t be any issue.
 
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