How are the LML's holding up?

elliottw

Member
Jan 23, 2013
397
6
13
ND
I finally got my truck back after getting a brand new motor installed. I opted to remove the CP4 and install at CP3 in its place since the CP4 is known to fail and wreck havoc on the fuel system.

Doing a complete fuel system replacement on an lml at work. You made the correct choice going with a cp3, I don't want an lml anymore lol
 

Big Block 88

Multiple choice muscle
Nov 3, 2008
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Does gm offer a cp4 replacement with a cp3.

If you have some spare time, get on ebay and look at used LML trucks... I see several with HUGE miles on them.

Ours is still kickin as a heavy hauler, no issues yet.
 

Dirtbag

New member
Sep 4, 2013
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Does gm offer a cp4 replacement with a cp3.

If you have some spare time, get on ebay and look at used LML trucks... I see several with HUGE miles on them.

Ours is still kickin as a heavy hauler, no issues yet.

No GM only offers a CP4 for the LML. Fleece Performance has developed a kit to allow you to replace the CP4 with a CP3. There are some fitment issues that require you to remove the EGR components and you also will need tuning to control it.

http://fleeceperformance.com/fuel-system/lml-cp3-conversion.html

So far it runs great and definetly has more power.
 

swaggerstick

New member
Aug 10, 2014
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Indana
Lml

:)used to have a 06 Duramax LBZ . Went back to 6.0 Gas in 2013. Huge Mistake. I just bought a 2015 Duramax. I only have around 900 miles on it but so far I love it. It is even quieter than the 06 was. Too early to tell about mileage but it is one heck of a truck.
 

GMfuelsystems

New member
Aug 31, 2014
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Greater Detroit area
The bosch fuel system is robust and as long as you get a cp4.2 pump with out roller issues its going to treat you well. Also its a 2000bar injection pump and it performs better than the cp3.. The piezoelectric injectors are bullet proof.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
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The bosch fuel system is robust and as long as you get a cp4.2 pump with out roller issues its going to treat you well. Also its a 2000bar injection pump and it performs better than the cp3.. The piezoelectric injectors are bullet proof.

I was told the cp4.2 on the 15's is redesigned. Can you elaborate if you can please? If it is going to be an issuse im going to swap in a cp3...
 

GMfuelsystems

New member
Aug 31, 2014
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Greater Detroit area
The CP4.2 2015

CP4.2 has been changed slightly, like coatings added to the cam and roller Assembly for less friction, the lift pump gear has been slightly changed. Ford 6.7 uses the same Injection pump but their cp4 pump has been stroked for fuel delivery, also Cummins 5.0 liter, AUDI V10 uses the CP4 pump as well. I don't recommend changing the CP4 pump with a cp3 pump for performance purpose's.
You will loose 2000bar capabilities, and if you are that worried about your pump failing remove the meteting valve or the filter between the supply and return ports located on the pump every so often to check debris.
 

DIESELMAFIAPER.LB7

<----new hotness
Jan 17, 2010
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CP4.2 has been changed slightly, like coatings added to the cam and roller Assembly for less friction, the lift pump gear has been slightly changed. Ford 6.7 uses the same Injection pump but their cp4 pump has been stroked for fuel delivery, also Cummins 5.0 liter, AUDI V10 uses the CP4 pump as well. I don't recommend changing the CP4 pump with a cp3 pump for performance purpose's.
You will loose 2000bar capabilities, and if you are that worried about your pump failing remove the meteting valve or the filter between the supply and return ports located on the pump every so often to check debris.

Fleece has already proven the cp3 to work well at the higher rail pressure and it drives nice from everything I've seen.

Just curious as to why you guys are using a pump that comes apart so easy and flows less volume? Also your saying fords cp4.2 flows more fuel? They don't seem to have as many faliure as gm trucks why is that?
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
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At Da Beach
Fleece has already proven the cp3 to work well at the higher rail pressure and it drives nice from everything I've seen.

Just curious as to why you guys are using a pump that comes apart so easy and flows less volume? Also your saying fords cp4.2 flows more fuel? They don't seem to have as many faliure as gm trucks why is that?

Why not just swap in a ford cp4.2... lol. Don't the fords have a factory lift pump?
 

DIESELMAFIAPER.LB7

<----new hotness
Jan 17, 2010
5,163
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shop.dieselmafiaperformance.com
Why not just swap in a ford cp4.2... lol. Don't the fords have a factory lift pump?

Cp3s are proven and if they grenaded they don't seem to ruin the rest the fuel system like cp4.2 does and yes I believe ford does have a factory lift pump and maybe it would be a worth while swap if they do flow more fuel and don't grenade as often I haven't paid much attention to that in the ford camp lol
 

Big Block 88

Multiple choice muscle
Nov 3, 2008
4,665
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CP4.2 has been changed slightly, like coatings added to the cam and roller Assembly for less friction, the lift pump gear has been slightly changed. Ford 6.7 uses the same Injection pump but their cp4 pump has been stroked for fuel delivery, also Cummins 5.0 liter, AUDI V10 uses the CP4 pump as well. I don't recommend changing the CP4 pump with a cp3 pump for performance purpose's.
You will loose 2000bar capabilities, and if you are that worried about your pump failing remove the meteting valve or the filter between the supply and return ports located on the pump every so often to check debris.


My question is why did GM skimp on the cp4 and ford did not? Piezo cant be all that reliable, I have heard of the piezo going away again.

You are saying the metering valve is the culprit for the failures? Did you all see any issues during testing? There must be a reason ford saw the need to stroke the pump, they are feeding 0.1 more litres than us and there "claimed numbers" are higher.

Is cummins and audi running our pumps or fords stroker pump?

I am merely curious, my signature shows our loyalty to your camp, and that is just a fraction of our rigs. I would like to feel GM has a good reason for doing the things they do other than it saves a few pennies...
 

carpenca

New member
Dec 17, 2010
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No GM only offers a CP4 for the LML. Fleece Performance has developed a kit to allow you to replace the CP4 with a CP3. There are some fitment issues that require you to remove the EGR components and you also will need tuning to control it.

http://fleeceperformance.com/fuel-system/lml-cp3-conversion.html

So far it runs great and definetly has more power.

Permanent removal of the EGR system is not necessary, and tuning may or may not be necessary depending on application. Over zealous CP3 selection leads to more tuning requirements.

Caleb
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,201
363
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At Da Beach
Permanent removal of the EGR system is not necessary, and tuning may or may not be necessary depending on application. Over zealous CP3 selection leads to more tuning requirements.

Caleb

I spoke to yall today about new tuning and the swap. I'm still debating it... :D
 

Warrenv

New member
Mar 9, 2019
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Opelousas, Louisiana
I have a 15+ and I had nothing but problems with it. Just out of warranty had to get head gaskets changed, then rear end started howling and in the process of ordering parts to repair had a piston either crack or a hole but will be doing a compression test in the morning to see which cylinder. I regret buying the truck. Bought it new and worked it from day one cause I lease it to the company I work for. I deleted egr and def with efi live tunes when def started acting up. Love the truck but too many issues. This is my 3rd Dmax. I started off with an 01 lb7 then an 07 lbz and now the 15+ lml and worked all of them the same with this company and issues with my lml only.
 

HeavyDuty204

New member
May 26, 2014
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Manitoba, CA
I owned an 11 LML that I bought new, never had an issue. That was with good tuning and sensible operation.

I can say that my buddies shop sees quite a few LMLs in for head gaskets, blown motors, CP4's and various other issues. Don't think I'd ever own one again.
 

04chase

Member
Mar 28, 2008
222
1
18
have a buddy with 400k on his 2011 lml

glowplugs
2 TCM's
deleted since 90k , pulls 4 car hauler 90% of the miles and all stock engine and trans still strong as ever.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,201
363
83
At Da Beach
LML is probably the best of the emissions motors. They built more than any other engine code so of course there will be more reported problems. Funny the consensus is lbz is best but they didn't build very many of them so it's not a fair comparison...