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Discussion Starter #1
I've been reading and researching this for a few weeks now and I'm getting concerned that my truck will eventually grenade.

Leads me to a few questions:
What are the actual chances of this happening to my truck?
Anything I can do to prevent it from happening (I presume no...or replace it with a CP3)
Any warning signs that it is dying?
How hard is it to replace the CP4 with a CP3? Is it something I can handle myself (with limited knowledge), or should I take it over to Merchant Auto and see if they will do it?

Anything would be helpful. There is just so much conflicting information about when it goes, how it goes,etc. It looks like it will go at some point, but I'd like to prepare before I have a $45,000 paperweight.
 

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How many miles on your truck? Any mods? Be careful what you read on the internet because sometimes the advice is tainted. Somewhere on this site there is a LML that is all stock and has over 700k on the clock with no mention of a failed cp4.
 

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Discussion Starter #3
Yeah I saw the 700k one. I only have emissions removed and tuned for that. I'm going to get a lift pump. I have 60k miles.
 

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There is a cp4 poll running on one of the other sites.

Last I looked, 185 had responded, and 14 had failures or 7.5%.

I suspect those with failures are a lot more likely to respond.

If it's your truck a failure is obviously not good, but it also apparent that don't fail near as often as some would have you believe.
 

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I would think if you use a lift pump to reduce strain on the pump, and decent filtration changed at reasonable intervals, then that may help. Not all that familiar with the LMLs in the first place, but it seems reasonable.
 
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There are issues with the new HPFP's but if I had to guess failure rates are probably less than 5%. To me even if it is 1% it is an issue because if they fail it is a catastrauphic failure that will cost a ton to fix. I'm not convinced this is gonna be a LB7 type issue where there is a high likelihood you'll have to replace injectors in almost every case, because there are some high mileage LML's out there with no fuel pump problems whatsoever.

From my research I think the best thing you can do is to try and get good fuel from a reputable place, use a Lubricity additive, change filters often, and don't tune it unless you run a lift pump.

No one I know has ever had an issue with the fuel system in an LML until just last week when my buddy was having issues starting his 2012. It wouldn't start on the first crank and even on the second attempt it was extended. He changed filters and it started ok, then he hauled some water to his cattle and filter life went from 100% to zero in just a few miles. Put another filter on now it won't even start. He had been using the plastic wix filter and admitted to me it had been a long time since he had changed the filter, like 30,000+ miles! My guess is he had a dirty or plugged filter and got some bad fuel and may have wrecked his pump. It only has 60K on it. He called the dealership and they said if he was using that Wix filter he may be screwed. He will find out this week what the damage is and I'll report as I am very curious.
 

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At my dealer we have only had 2 fail requiring fuel system replacements and another one that wouldn't build pressure - just a bad pump no major failure. We sell and service lots of diesels so I don't think it's as common as what the Internet makes it look like.
 

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As i stated in my Build Thread. I am not aware that the CP4 on my truck has been replaced. I am certain it is original. And as far as i can tell he had a lift pump installed.As everyone else on here will tell you a lift pump will definitely help prevent premature failure of the CP4. That should of been the first thing i put back on the truck.
 

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Discussion Starter #9
I'm definitely looking at the FASS Titanium, but my question is the 150 vs 95. I dont want to damage anything by going to the 150, I dont ever plan on going over 600HP. I dont know what my current HP is, but its a mostly stock truck with emissions deleted (straight piped) and EFI Live tuning. I usually run the first or second tune (one is slightly over stock the other is towing).

Thoughts on that. I got the OK to pull the trigger from the wife, but dont know which to go for!
 

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Thats pretty much how my truck is setup. And I too have been wondering the 150 or 95! From what i gather. Anyone that has a bone stock truck and plans on keeping it that way has been using the 95. For those of us that have deleted and tuned it seems they are going to the 150. I haven't read or heard of the 150 doing any damage. Price wise its a small step up to the 150 so that is what i am leaning towards.
 

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Im not 100% sure. But i think it has only been on 2011 and newer due it being the new CP4. But mainly the 11's and 12's. There hasn't been many just a few. I haven't heard of a pin pointed out reason as to why these few have failed. Other then defective. Maybe bad Fuel, Not using proper additive, or because of abusing the CP4 to well over its capabilities.
 

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The thing about Modding a truck or any vehicle for that matter is every part of the engine has its limits. With doing upgrade to these trucks. Deleting the emission, adding a tuner that increases the fuel % to the injectors can over-work a CP4. Since there is no fuel pump that pump is working overtime to suck the fuel from the tank. Adding a lift pump simply aids the CP4. Depending on the end goal of your truck will determine whether or not the factory CP4 should be upgraded or converted to the Cp3.
 

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Discussion Starter #14
My end goal for the truck is to have a reliable vehicle to keep for a long time. I'll pull my 5er and that's about it. Mostly a DD
 

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Thats my end goal! I will hopefully within a few years have a nice camper to haul around. But Id say since you got the OK from the wife. Pull that trigger. I think am going to go with the FASS150. Just because i am tuned and do plan on doing some more mods in the future. and this way i am already covered for those future upgrades
 

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Discussion Starter #16
I'm also looking at the air dog ii 165. I really like the no drill install of the titanium though, and that will (as dumb as it sounds) probably be the deciding factor
 

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Yea i do like the Air Dog. Especially since they have the quick disconnect for the duramax. Definitely makes the job easier. I was unaware of the no drill install from the titanium. Ill have to check that out again.
 

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At my dealer we have only had 2 fail requiring fuel system replacements and another one that wouldn't build pressure - just a bad pump no major failure. We sell and service lots of diesels so I don't think it's as common as what the Internet makes it look like.

What is interesting is that I have read where Canadian blended fuel has more additives and a lower SCAR rating compared to American blended fuel, hence failures have been less common up north. Don't know if there is any truth to that or not.

One thing I can't seem to nail down is that supposedly the 2015 pickups have an "updated" CP4 but I haven't been able to determine what the update is or whether the update is even true? In addition I can't remember where I saw this but I thought I read that someone with a new 2015 has had a failure. However, most of the failures I have read about have been the 2011-2012 models. That would tend to make more sense as those theoretically should have more miles.
 

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That is interesting Doodle! I'll have to research for this "updated CP4". I'd be interested in knowing what the update is and it if it something that could be available for the 2011-2014 models. You would think after 4-5 years of these new CP4 pumps being in the newer trucks they would have some clue or idea of what exactly is causing the rare few to fail.
 

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I'm not expert, but I think the failures are primarily due to the higher pressures the Cp4 runs at and the the lower tolerance for any contamination (i.e. water) in the fuel. So if you get bad fuel and don't have good filtration, pump life could be comprimised. I read somewhere that Bosch only warranties the Cp4 for like 1000 hours. That is a bit misleading because some have tanken it like it has a service life of only 1000 hours. However, I would suspect that service life for the Cp4 won't be nearly as long as the more reliable Cp3. That is why there are some doing conversions. At the end of the day sometimes you just have to play the law of averages and figure with good maintainance you are unlikely to have issues with the Cp4 or convert it to the Cp3.
 
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