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Discussion Starter #1 (Edited)
Decided to go ahead and replace the fuel filter today. It still had "38% remaining" but I've already had two oil changes (about 12,500 miles) and I did have an incident last winter that I believe is attributable to fuel gelatinization. A couple of observations:

1) My (old) fuel filter had an actual tear in the filament; see below.



2) There appears to be a drain plug in the fuel filter housing which is only supposed to be tightened to 2.5 N*m, which is less than 2 lb*ft of torque. This is an incredibly tiny amount of torque and unless you have a 1/4" torque wrench you probably will not be able to tighten it correctly. The threads holding this drain plug in are tiny and appear to be very easy to strip. It's probably easier to just remove the entire filter housing with a drip pan under the thing, slowly lower it down, and pour the contents out into the drip pan than to screw around with the stupid drain plug. Who knows what GM charges for a replacement filter housing and drain plug if you strip the threads (I guarantee it's three figures). See below; let me know your thoughts.

Edit: Okay, this appears to be a drain for removing water from the fuel. In any case, make sure you have a tiny 1/4" drive torque wrench (torque measured in in*lbs) for draining water. A 3/8" drive wrench will probably not have small enough adjustments to keep you from stripping these threads. I discourage anyone from tightening it "just enough" (without a torque wrench) because you'll almost certainly over-tighten it and hop/strip the threads.

Edit: If you do strip it, it's not the end of the world: https://www.ebay.com/itm/New-GM-Fuel-Water-Separator-Filter-Assembly-2017-2018-Silverado-Duramax-23149526-/202163738516



3) After I put everything back together, I fired 'er up to check for leaks. I was worried because when I was screwing around with the drain plug I over-tightened it and the threads "hopped," and my heart skipped a beat because I thought I'd stripped them. Fortunately it seems to be working fine; I let it idle for about twenty minutes with a drip pan underneath and didn't see any issues. However, I noticed for the first time a noise that seems to be coming from the fuel tank area; it sounds like a pump trying to suck liquid out of something but with the intake only partially submerged (my fuel tank is 3/4 full in the video below). It is a little hard to hear because of the sound of the engine, but in the background you should be able to make out the sound I'm describing. Does anyone know what that is?


4) I was unable to get a picture of this due to the angles involved, but there appears to be some kind of heat exchanger connected to the fuel system. It's near the fuel filter. Can anyone explain what that thing is, and what it does?
 

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Can't say I hear the noise. The heat exchanger is the fuel cooler, been there at least since the LLY's which is as far back as my knowledge goes.

Keep listening to the noise and for kicks I'll go and check mine. I'm due to change my filter this week or weekend and I'll let you know what I hear. I wouldn't necessarily worry about it though. For comparative purposes I'm just at 13K miles and Fuel Filter life is like 15%. I used to change filters at 12K on my other trucks so I'll just pick that up again on this one.

Another thing you could do is PM this guy called Berettaman (???) Can't believe I remember his name but he had an issue with his pump making tons of noise and see how that was resolved. Thread is on here somewhere.

As for the torque just use a 1/4 inch socket and go until "tight" . I am a bicycle rider and everything on higher end bikes has a torque reading due to the carbon fiber tubes and hence I have a 1/4 torque wrench for that stuff. 2 N-M is just tight with a 1/4 inch like 3" long ratchet. 4 N-M with that 6" long torque wrench and you have to push it a little. Pardon my hack but it will work. Your method though of just pulling the whole housing works as well.
 

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Discussion Starter #3
Can't say I hear the noise. The heat exchanger is the fuel cooler, been there at least since the LLY's which is as far back as my knowledge goes.

Keep listening to the noise and for kicks I'll go and check mine. I'm due to change my filter this week or weekend and I'll let you know what I hear. I wouldn't necessarily worry about it though. Another thing you could do is PM this guy called Berettaman (???) Can't believe I remember his name but he had an issue with his pump making tons of noise and see how that was resolved. Thread is on here somewhere.

As for the torque just use a 1/4 inch socket and go until "tight" . I am a bicycle rider and everything on higher end bikes has a torque reading due to the carbon fiber tubes and hence I have a 1/4 torque wrench for that stuff. 2 N-M is just tight with a 1/4 inch like 3" long ratchet. 4 N-M with that 6" long torque wrench and you have to push it a little. Pardon my hack but it will work. Your method though of just pulling the whole housing works as well.
Yeah, I went ahead and ordered a 1/4" torque wrench. I already have 3/8" and 1/2" so this will complete the trifecta. The truck runs fine and there are no leaks based on the little bit of driving I did yesterday after finishing the filter change. Thanks for the info on the fuel cooler; this is my first Duramax so I'm still in the learning phase.
 

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LML's didn't have a fuel cooler, but the mount location was there, IIRC.

Sorta like they were hedging there bets...same as the steering damper, that wasn't there when they released the new frame/chassis in 2011 -- but also had the mount location.
 

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JD,

I checked mine today and I don't hear any noise but I did think of a bit of a simple test for you. Drain the filter again. Then while your underneath and doing your filming thing, have somebody do the priming of the filter via the procedure outlined in the manual. I think it is just cycling the key w/o trying to start it. If there is some funky noise you should hear it then because it has to pump to re-prime.

If it was making a noise, take video to dealer, tell them procedure and maybe get it fixed that way. Sounds ambitious but might all in all work.
 

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Discussion Starter #7 (Edited)
JD,

I checked mine today and I don't hear any noise but I did think of a bit of a simple test for you. Drain the filter again. Then while your underneath and doing your filming thing, have somebody do the priming of the filter via the procedure outlined in the manual. I think it is just cycling the key w/o trying to start it. If there is some funky noise you should hear it then because it has to pump to re-prime.
So I heard the priming very clearly after I installed the new filter; I turned the key to "on" and you could hear the whine as the lift pump pressurized the fuel lines up to the injector pump. The noise I was referring to is something different, and I think it's actually been there all the time, I just never really paid attention to it before. Everything seems to be running fine and the CEL hasn't come on, so it's probably nothing. If you see a familiar-looking white L5P CCSB on the side of 287 over the next couple of days you'll know I was wrong.

Edit: I bet I know what that noise is after all. I think it's probably the sound of the fuel being sprayed back into the fuel tank from the return line. Just a guess, though.
 

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Quick question. if I am changing the fuel filter with the larger diameter bolt on the fuel filter housing, do I need to worry about the 1/4 in bolt that is where the water drain plug is in the center? I do alot of pulling and I have new filter and o-rings. I got a quote from the dealer at 160.00 and I was like whoa... FIgured I could do it, as I have a 1/2in Torque wrench to change it, and it auto primes after when you turn the key "on". Looking for confirmation on the water separation. Lastly, I know Cummins has 2 filters, one near the fuel tank and one in the engine compartment. Want to confirm there is only one on my Duramax in my 2018 Denali HD.

Thanks in Advance
 

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Traded in my '09 for an '18 and just was looking for the priming procedure, seeing how it would be heck to try to get at the top of the canister to blead the air. So, … looks like all I have to do is screw off the housing, change filter element, replace o-ring, tighten housing, turn key to on, wait a bit before starting. Right? Nice to not have to remove a fender liner and WIF connection. Do we still have a WIF capability? Guess I need to order the Tech Manuals and do some reading. Things changed a bit in 9 years. Anybody want some '09 tech manuals, all 26#s.
 

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Discussion Starter #10
Traded in my '09 for an '18 and just was looking for the priming procedure, seeing how it would be heck to try to get at the top of the canister to blead the air. So, … looks like all I have to do is screw off the housing, change filter element, replace o-ring, tighten housing, turn key to on, wait a bit before starting. Right? Nice to not have to remove a fender liner and WIF connection. Do we still have a WIF capability? Guess I need to order the Tech Manuals and do some reading. Things changed a bit in 9 years. Anybody want some '09 tech manuals, all 26#s.
Pretty much; the priming is handled automatically. The filter bowl functions as a fuel/water separator too. There's a tiny little nut at the base that you can unthread and the contents of the bowl will pour out. I think it's rated for 2.5 lb*ft so be very delicate and/or use a little 1/4" drive torque wrench.
 

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Discussion Starter #11
Quick question. if I am changing the fuel filter with the larger diameter bolt on the fuel filter housing, do I need to worry about the 1/4 in bolt that is where the water drain plug is in the center? I do alot of pulling and I have new filter and o-rings. I got a quote from the dealer at 160.00 and I was like whoa... FIgured I could do it, as I have a 1/2in Torque wrench to change it, and it auto primes after when you turn the key "on". Looking for confirmation on the water separation. Lastly, I know Cummins has 2 filters, one near the fuel tank and one in the engine compartment. Want to confirm there is only one on my Duramax in my 2018 Denali HD.

Thanks in Advance
There's only one filter (to my knowledge), and you don't need to worry about the small drain plug if you're removing the whole filter bowl anyway. The nice thing about it (aside from being able to drain water out of the system) is that if you drain the bowl first you won't have a cup of diesel pouring all over the place.
 

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When I changed the filter on both the 17 and the 18, I opened the drain and waited. Never really quit draining. Fuel filter is below fuel level of the tank and the pump is flow through so it kept pouring fuel out on me while doing the change. I did put my pinch off pliers on it to stop it so I could change the little o-ring.
 

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Discussion Starter #13
When I changed the filter on both the 17 and the 18, I opened the drain and waited. Never really quit draining. Fuel filter is below fuel level of the tank and the pump is flow through so it kept pouring fuel out on me while doing the change. I did put my pinch off pliers on it to stop it so I could change the little o-ring.
That makes sense. I thought maybe the in-tank pump would prevent it from free-flowing, but I guess not. I know that when I did it I didn't even see the little drain plug and just took the whole thing off.
 

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And do the key cycle twice. Key on 30sec, key off, key on 30 sec then start. It may still idle little rough for a few minutes.
 

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I took the filler cap off and listened for the bubbles to stop. IIRC took 2 cycles for the bubbling to start and 1 more for ti to stop. 4 cycles in all.
 

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GM's version:

Priming the Fuel System

There is an electric priming pump
that will bring fuel to the engine and
eliminate air in the fuel lines.

To prime the engine:

1. Correct any condition that caused the loss of prime.

2. Turn the ignition on for 30 seconds.
Do not start the engine. The fuel pump will start priming.

3. Turn the ignition off, then back to start, and crank the engine for 15 seconds.

4. If the engine does not start, repeat Steps 2 and 3 until the engine starts.

If the engine does not start after repeating Steps 2 and 3 three times, turn the ignition off for 60 seconds.

5. Repeat the above steps until the engine starts.

6. If the engine starts, but does not run smoothly, increase the engine speed slightly.

7. If the engine starts and runs but stalls again, turn the ignition off for 60 seconds.

8. When the engine starts, let it idle for a few minutes and check the filter for any leaks.
 

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Changed my fuel filter today @ 13,450 miles @ 29% fuel filter life left per DIC.......priming procedure went well, and like original poster seems I can hear fuel returning to fuel tank, which I didn't hear before.
 
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