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broke my new Dmax

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so I drove from CDA,ID to crosby north dakota and on my way back (im in bozemen,MT now) I noticed a clack that sounds out of place. no engine lights,no smoke, egts ranged from 550 to 1100 degrees. happens only when theres a load on the engine above 1700 rpms, at least thats when its loud enough to hear it and the engine has what feels like a slight miss most noticeable around 2k rpm (been doing 75mph all day) and on take off getting on the freeway. any ideas?

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ive read that an injector can sound like a rod knock so im hoping, the PO had them replaced 35k miles ago but sshhhttt happens, didnt loose any power thats for sure

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take em out and with the right equipment pressure fuel thru while reading a pressure guage, on the old 12v ones..... but common rail, i havent a clue.......... i'd like to watch cr injectors go thru this test.

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LB7, LLY, LBZ??? What DMax motor you running? LB7's are notorious for injector problems, but with what you're dealing with I would expect more noticeable symptoms. Is there any white smoke while running, or fuel in the oil? Couple good signs of injector problems. They do 'tick, tick, tick, tick' like a typewriter as well. GM says nothing you can do about it on the LB7, but it's annoying because everyone thinks something is wrong with the engine. That will not affect anything performance-wise though. Not very knowledgeable about things on '04.5 year motors or newer or I would try to help more.

racer

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I'd have someone do an injector kill test with a scan tool if your thinking injectors (that way you can see if one or more are obviously bad or if you should look elsewhere). We can do the injector kill test and actually test your injectors on a test bench at mastertech diesel in Boise. We actually rebuild common rail injectors in house as well. Our number is 327-0001. Just let me know if the site isn't cool with this Mudster I'm just trying to help out a member though.

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LB7, LLY, LBZ??? What DMax motor you running? LB7's are notorious for injector problems, but with what you're dealing with I would expect more noticeable symptoms. Is there any white smoke while running, or fuel in the oil? Couple good signs of injector problems. They do 'tick, tick, tick, tick' like a typewriter as well. GM says nothing you can do about it on the LB7, but it's annoying because everyone thinks something is wrong with the engine. That will not affect anything performance-wise though. Not very knowledgeable about things on '04.5 year motors or newer or I would try to help more.

racer

mines a 2001 LB7, the injectors are relativly new according to the owners manual were the PO had writen it down but ssshht still happens. to be honest the noise im hearing sounds just like a gas motor with a bad rod and considering im married to the bank for 3 years id be super pissed if it was but I imagine a rod knock would be killer lound on a diesel. oil pressure is just fine 40 at lidle and 65 cruising at 70mph. no power loss, not even a hint of smoke even when getting on the highway

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I'd have someone do an injector kill test with a scan tool if your thinking injectors (that way you can see if one or more are obviously bad or if you should look elsewhere). We can do the injector kill test and actually test your injectors on a test bench at mastertech diesel in Boise. We actually rebuild common rail injectors in house as well. Our number is 327-0001. Just let me know if the site isn't cool with this Mudster I'm just trying to help out a member though.

sweet thanks man i will keep that in mind if i need work

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You know, why don't you go ahead and buy a new oil filter. Put it on the truck and then cut open your old one to look for 'sparkly', expensive metal parts in the filter media (Keep in mind that you need to not make any metal shavings when you cut it open!). Most quick lube places have a filter cutter that works like a large tubing cutter and won't make any metal shavings at all. This way you can quickly rule out whether you need to stop running this engine or not! If the old filter comes out clean then you could go have an injector shut down test performed to see if you can tell which one(s) is / are causing the problem(s). Unless you know someone, that test will cost you some shop time usually.

How would you describe the noise? Most of the time a fuel knock in a diesel sounds like a rod is ready to come out the side of the block (loud and 'deep' or serious sounding). If it is more of a ticking sound or a lighter and 'tinny' sound then maybe it is one of the injectors making that noise.

If it is not a fuel knock and the oil filter media is clean of any metal shavings, hopefully you will be fine driving it that way. How far have you driven it with it making this noise? Has the noise changed any since you noticed it?

(The test bench for testing these CR injectors is just a little more complicated than what is used to test the older mechanical injectors. You have to 'plug' in the injector so you can control when it fires electrically and of course the pressure must be higher and constantly applied. The old mechanical injectors were fired by the fuel pressure which was usually between 2000 and 4000 psi [depending on the design of the system]. These newer CR injectors usually use a low pressure of at least 4000 and can run up to over 20,000 psi when under full load demand. The 'pop' of the mechanical injector is impressive in person! I kind of wanted to have an ignition source near the mist to see how easy it is to light. . . . . :popcorn:

I've never seen a CR injector tested. I have to wonder if the fuel cloud isn't more impressive because of the higher pressures involved!! Wonder if POWER Freak could make us a video from the test bench . . . :think: )

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Check your oil level for diesel in it, easiest way to yell if its injector, my guess is yes. You can take it to the dealer and hook it up they can do a balance rate test and pinpoint the bad one for you

Sent from my DROIDX

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thats a great idea on the filter, my father inlaw is a plumber so i bet he has a pipe cutter that big i can use. I noticed it on my way back from a job in north dakota (800miles), but i cant for the life of me remember if that noise was there before or not. i should go find another Dmax and see if i hear the noise in another truck. the noise has been consistant: louder under a load, much quiter when cruising. maybe im being paranoid I need a nother western member to come hear this noise with me!!!!!:wall:

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My LB7 has a light tick to it as well, and has since I bought it... Everyone says it's nothing to worry about, and that it's really common on LB7's. However, I have alot of buddies who ended up having injectors go out on theirs.

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so 2 micron filtration and adding absolutly no rail pressure increase should help the common rail injectors in the dmax live longer. correct??????

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so 2 micron filtration and adding absolutly no rail pressure increase should help the common rail injectors in the dmax live longer. correct??????

Yes, and adding a better fuel pump will help even more.

-Kris

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thanks guys for all the help, my family heavy diesel mechanic says its slightly louder than hes heard but the sound is normal and i shouldnt get all freaked out. so im just being a paranoid first time diesel owner

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The biggest thing is filtration muddy. I've looked at tons of valve sets with a microscope out of Cummins' and Duramax motors and they have almost all failed due to contamination eroding the valve seat.

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