@An extremely important man neither it run's fine and great peace of mind.

@An extremely important man My truck is bone stock,I didn,t feel a difference with power, i mainly did for protection if the pump take's a shit but i read on some truck web site that this does not help.

But you’re still running on the OEM CP4? I’m in the market for a new tow vehicle and am looking at “higher” mileage LMLs. This failure is my biggest concern obviously

@@marshallangst8780 since my last post based in the price of used and new trucks currently, It was worth spending some extra cash on our truck. We installed a fleece CP3 conversion kit and SOTF tuning, we use it to haul horses between NC and FL so reliability was key, we get approx 17mpg hauling and 20mpg unloaded which is slight improvement from stock.

James, do you have a lift pump installed? Do you use a fuel additive?

@@davidpeace34 Hi David, I've always used a fuel additive thinking that added lubricity would help extend the life of my CP4 pump. I'm using Diesel Kleen, either summer or winter blend as appropriate. I have no empirical data to offer regarding how effective it is, but at least it makes me feel better, and so far so good at 171,000 miles! Other additives, such as StanaDyne, offer similar benefits. There's a lot of information on the forums about the benefits and relative strengths of various additives. I've looked at a lift pump, but have not installed one yet. It's on my wish list! Given the overall circumstances, I'm leaning toward a Kennedy, because it'll provide adequate head pressure for my stock LML, and because it won't strand me in case of an internal pump failure. Overall, I'm using the "can't hurt, might help" attitude on the lift pump issue. Again, lots of debate and good information on the forums.

I have a 2011 LmL deleted at 80,000 miles i now have 257,000 miles on it and just had to replace the fuse box under the hood other then normal maintenance items. All original injectors and cp4 everything, just emissions delete only. I ran power Service in the fuel the 1st half of its life and the past 3 years I have switched to Amsoil all in 1 diesel additive. I believe the problem with cp4 is guys run these hot tunes or even a 75hp tune and hold the truck wide open pulling grades, and the fuel system is over worked and can’t keep up. The cp4 has 2 pistons that move and the fuel is the lubricant for it, I think the power service and amsoil keeps everything slick even with this low sulfur fuel that has less lubricity

Hi David, Just FYI, I'm at 197,000 with no CP4 problem, bit plenty of emissions system issues. All fixable, but expensive. Just installed an AirDog II 4G system and Beans fuel tank sump.

5000miles per year? Oh man I'm putting 40,000 per year

There’s a couple links of it working. Still will send metal to the tank and line. But protected injectors and stuff. Went from a 10,000 dollar job to a 2300 dollar job.

My buddy a few days ago, took it to the shop to fix a problem, cp4 blew. Luckily the week before he brought it in the fuel saver was installed

Yes probably, the compressor is not technically in the way, though having it removed is kind of nice because it simply gives you more room to work. Honestly for the 10 minutes or less it takes to remove and reinstall it, I would probably just go ahead and move it out of the way. You dont have to disconnect the AC lines, just fold them over and out of the way, so there is no loss of freon.

@@FixedVaneDuramax appreciate the reply. I'll probably go ahead and move it out of the way. I'm just lazy 😂😂

No, you’re just unbolting the compressor and moving it out of the way, you don’t need to disconnect the lines so the system remains sealed.

With those hard lines didn’t think that would be doable

Do you have a link to the valve and cost $$$ ???

Later bodystyles meaning the 2015-2017 LMLs? In that case yes. If you are referring to the L5P trucks, they are a completely different fuel system that does not require this modification.

Good question for sure. The CP4 issue is really a bit of a toss up, some guys have run them for 100s of thousands of miles without issue, other guys had had nightmare experiences where the pump grenades and takes out the entire downstream fuel system. My neighbor down the road had his cp4 go out, the local dealer replaced it along with the rest of the system under warranty. Literally a couple thousand miles later the new cp4 went out and did it all over again. He did a cp3 conversion at that point. Here is a link to S&S Diesel's (one of the best aftermarket fuel system companies in the industry) CP3 conversion, they have an option for a 50 state legal, no tuning required system. That package is $1780, though you would still have to install it yourself or pay to have it installed. So you have several options, you can either wait and see what happens (install the fuel system saver in this video in this case), or you can spend a few grand and have the cp3 conversion completed and give yourself peace of mind and have a very reliable truck. Or, you could sell the truck and relieve yourself of the potential issue entirely. ssdiesel.com/product/lml-cp3-conversions/

Cp3

My dealer tells me that GM guidance says 12-16 man hours for the pump and under hood work. Add in the fuel tank and lines, it'll likely be 3 days in the shop.

Sorry, my previous reply was for a full CP4 replacement effort following pump failure. To install the FPR replacement alone took me just over 3 hours.

@@jamesclark7248 no worries. I seen both comments and figured that’s what you meant. I went looking last night on how to replace CP4 videos or CP4 to CP3 swaps and DAM , that’s definitely no easy or small task and I’m definitely not feeling confident on it ,

@@jasonjackson329 Hi Jason, Thanks! My guess is as follows; 3 hours for the FPR swap only, 2 days and about $5k for the 50 state & CARB compliant CP4 to CP3 conversion, and about $12k to repair the whole fuel system after a CP4 catastrophic failure. All of this is based on postings on the Duramax forums and my dealer estimates for a pro installation.

lol

I have seen the same thing from some big name shops, these dont work !

I agree I don’t see how it’s doing anything. 20 micron is definitely going to mess up some injectors

Are you throwing any codes? Is your CEL illuminated? Does your glow plug light come on and go off normally? Any other symptoms?

Same here. System is primed, no error codes. Bled the Schrader valve. Crank no start. Prime pump feels firm and doesnt seem like an air leak.

@@kevicook Believe it or not mine turned out to be a bad cp4. I had the whole fuel system replaced in Nov of 2020.

@@jfromstatefarm2345 I still haven't got my truck started. I thought bad CP4 as well, but it was working perfect before I replaced the FPR. I hooked the fuel system up to a diesel can. Tried priming and noted air bubbles returning through both the return line and the supply line. Seems to be an air leak. But I dont know where. And I didnt remove any hoses during the install. Im completely stumped. Also, return fuel when cranking looks like it went through a blender. The only indication I have right now that the CP4 is in fact functioning.

@@kevicook is there a way you can hook a scan tool and check desired vs actual fuel rail pressure. That will sure tell if your pump is gone or not

Good questions..so in 2012 GM started using the next generation of cam driven high pressure fuel pumps known as the CP4 pump. Capable of slightly higher pressures but much more prone to failure, and unfortunately they fail catastrophically, sending shards of the pump downstream to the injectors which can cause further very expensive failures. Several different companies offer CP3 conversions which allows the customer to install the previous generation of high pressure pump, which has proven to be exceptionally reliable in pretty much every common rail diesel application since the early 2000s.

www.wcfab.com/i-31420523-exergy-performance-system-saver-improved-stock-inlet-metering-valve-fca-mprop.html?ref=category:1378224

Thank you

Show me a filter that can hold 29K psi and youll find your answer lol

Link to the part number is in the description.