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Lift pump and filter assembly LML Duramax

Future project plan to fabricate a remote fuel filter base and lift pump

Would you do a DIY filter base & lift pump or buy a pre-fabricated one?

Poll ended at Feb 23 2021, 11:44pm

FASS Titanium Series/AirDog Air Fuel Separator
4
100%
DIY filter base and budget lift pump
0
No votes
 
Total votes : 4

Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 24 2021, 11:44pm

Just wanted to post a topic about a future plan I'm starting on my 2015 GMC Sierra 2500HD 6.6L LML.

I'm sure like most of you guys/gals on the forum; you don't have an unlimited budget for truck projects. So here is my plan.

1. Install a Fass DMAX 7002 lift pump
2. building a remote fuel filter base
- Baldwin FB46185 Fuel Filter Base
- 1/2' barb to 1/2" NPT aircraft grade alum.
- Baldwin BF7633 fuel filter (or additional water/fuel separator)

Instead of using the inline filter that comes with the DMAX 7002 that needs to be replaced every 5,000 miles (aka oil change) with hose clamps and a mess. I can build a spin on filter base that can be changed approx. 30,000 miles for around $35 with less mess.

I've done a lot of research and I realize that adding additional filter and a lift pump is more of an assurance than a necessity. I add a fuel lubricant at every fill up and I keep up with the maintenance; which is more than sufficient from what I've seen and read.

Let me know your thoughts/experiences. Whether this is overkill or if you'd just spend the extra cash for a Airdog or Fass filter & pump combo.

Also this is my first time creating a poll, we'll see how this works.......... :shock:
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Re: Lift pump and filter assembly LML Duramax

Postby 19trax95 » Jan 24 2021, 11:59pm

Personally the added filtration and water separation is absolutely key. Especially if you still have the cp4. Lubrication is part of the potential issue, but contamination is perhaps the biggest problem with the cp4. Any form or debris, or especially water, is a sure killer for the pump.

I'd get either a fass or airdog. They are proven and work great. I run a fass 95 on my truck currently. I may need to upgrade to a 165 in the future but for now the 95 is working flawlessly. I ditched the cp4 entirely but the benefits of a lift pump help with any fuel system.

A slightly lesser known option is the Kenedy pumps. They are a little less money than the fass or airdog, and you need to add your own filters, but they are supposed to be a solid option as well. I don't have any personal experience with them, but a bunch of guys over on the duramax forums have a hard on for them so it may be something worth looking into.

Between the two, fass and airdog, the air dog is a little easier to install. I don't like the way the air dog mounts at all, but that can easily be changed with either a custom mount or one of the aftermarket relocation kits. But both pumps are quiet (the current generations) and both would serve you well.
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Re: Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 25 2021, 2:46am

I have looked into the Kennedy pumps and they seem solid. I've seen a pretty divided number of responses from different consumers. The only reason I haven't considered Kennedy is I really don't feel like dropping the fuel tank or taking the bed off. Also I am not in a place where I have access to do so.

The idea of getting the tank to 1/4 full and dropping it also concerns me because that seems to be when issues arise with the fuel pump suctioning air and then hits the wall.

I feel the need to add another filter is critical too and adding a boost pump. C****ns uses a lift pump on all there engines; not sure why Duramax chose not to use it on the LML.
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Re: Lift pump and filter assembly LML Duramax

Postby 19trax95 » Jan 25 2021, 3:26am

You don't need to drop the tank or take the bed off necessarily for the air dog or Kenedy options. The fass you could probably get away with using the factory suction as well but I used the draw straw.

I installed an airdog 100 on my buddies truck in about 2 hours start to finish. The hardest part was getting the factory line to let go of the sending unit. After that the install went super quick and easy.

For my fass, I took the bed off and removed the fuel module in the tank to install the draw straw. That took me almost a day. Didn't speed things up that I did it on a frigid January day though lol.

The Kenedy installs very similarly to the airdog.

Another option is a sump. But that obviously involves permanently modification to the fuel tank.

As far as 1/4 tank issues, the fass with the draw straw eliminates that as long as its installed correctly. The air dog and Kenedy use the factory suction side so that would potentially be an issue with them. I have ran mine down until the light came on just to test it to make sure I wouldn't have issues, and I had no problems at all. I have my draw straw setup to be a hair lower than the factory pickup is.


And yeah, F*** and D**** have used a "lift" pump for a long time now. GM finally got with it on the L5P trucks.
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Re: Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 25 2021, 3:35am

I just got done looking up quite a few other posts on other sites about Kennedy. I think I am going to look into Kennedy some more. Most of the other posts I've seen are guys doing exactly what I'd like to do. (pre-filter > pump) The only thing I saw on Kennedy that is that they don't add a relay with the wiring hook up. A pretty easy fix.

Otherwise I like that the Kennedy deluxe kit comes with a mounting bracket. Whereas FASS doesn't. I have looked seriously into AirDog for awhile now too. However, I'm leaning more towards Kennedy. I'll have to do some more research.

I'll continue to keep everyone posted.
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Re: Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 29 2021, 3:17am

Okay, I’ve done a lot of reading and research in the past few days. I’ve spoke with several guys at work that have backyard and tech degrees in Diesel engines.

Here’s what I’ve surmised. Most diesels (including commercial diesels and marine) use some sort of lift pump in conjunction with the high pressure injector pump. Aviation turbine engines also use a similar set up as well with a submerged fuel boost pump with an engine driven pump.

Anyway. FASS/AirDog uses a gearator style pump that has a metal to metal contact which is made that way to separate and filter contamination. They operate at higher psi (approx 8-10 or higher depending on model) but not necessarily high flow.

Kennedy pumps are centrifugal flow through pumps. They do not have metal to metal contact, thus flow is not turbulent. Fluid is moved through in larger volume at a lower psi (approx 4psi).

Gearator pump pros: moves higher psi needed for constant pressure for high range HP engines. Separates fuel through gearation for water separation and filtering (at least for the FWS/Filter pump set up). Easy to prime system.

Gearator cons: high psi at the injector pump when the pump doesn’t need the fuel = most is returned to the tank. Possible issues with foaming (nil to negligible) in the tank. Pump goes out, possible hydro static lock and fuel starvation. Metal metal contact will generate chips, that’s why you have two filters.

Centrifugal pumps pros: operates and adjusts flow as needed by throttle response/main fuel pump needs. Flow through design allows fuel to flow even if lift pump fails. Requires no filtration/seperator prior to pump. Centrifugal pumps tend to last longer due to the very few moving parts as well. Operation is near silent.

Centrifugal cons: difficult to bleed at first and can be very tedious. Difficult to know what psi they are working at unless you have a gauge installed inline (negligible) or if it’s working due to how quiet it is.

So with all that said. I’ve decided to go with a Kennedy lift pump. I’ll share my initial design set up. It won’t be super sexy, but it’ll be simple and effective.
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Re: Lift pump and filter assembly LML Duramax

Postby 19trax95 » Jan 29 2021, 3:30am

Just some points to add.

The high pressure pumps do have a small built in lift pump on them. However, it needs to work rather hard, which can lead to either cavitation, or it simply not being able to supply enough fuel and you'll drain your fuel rails before the pump can keep up. Neither case is good.


Both the fass and airdog will flow through if the pump motor were to stop working. I have tested this on mine by pulling the fuse and the truck still starts and runs fine.


8-10 psi is the max recommended pressure for the duramax platform. Much higher and you can run into issues. But one of the "benefits" of having say a 100gph pump and then using only a portion of that to supply the engine, is that it will "polish" the fuel. Meaning that it still filters and removes water from the fuel that isn't being used by the engine. This isn't super important since the main goal is to assure the engine gets a clean supply of fuel, but rather its a helpful side effect.

But I don't think you'll go wrong with the Kennedy setup. Just pick good filters, and you should be good to go.
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Re: Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 29 2021, 3:47am

Agreed, I think just about anything will be helpful to extend the live of the CP4.2 pump.

Side note; this topic follows under the same category of essential oils/snake oil, UFOs and Elvis. There is a lot of speculation with some snips of science and research to back it up.

The topic of fuel filters on the duramax forums, geez. Basically one side of the house is all CAT/Baldwin and the other side is all Rancor. They feel pretty strongly about there filters...... And everything else, haha. God Bless the freedom of speech.
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Re: Lift pump and filter assembly LML Duramax

Postby 19trax95 » Jan 29 2021, 3:56am

Yeah there are pages upon pages of back and forth on filters.

I don't know of you've seen it, but a member on the duramax forum put together a nice thread comparing the build quality and filtration of all the common oil and fuel filters. Proves you don't need to spend a ton to get a quality filter all the time.
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Re: Lift pump and filter assembly LML Duramax

Postby ColdIronAxe [OP] » Jan 29 2021, 4:05am

Here is the basic diagram that I can up with while researching the topic. The idea is simple to install and remove back to OEM if needed with little fabrication or modification. The filter mount and pump will attach to the mount that comes with the Kennedy single deluxe kit. I know that I draw like a kid, because I'm still a kid at heart who likes to play with trucks.

tank hose > 1/2" barb to 1/2" NPT to Kennedy single pump > 1/2' NPT male threaded union >Baldwin FB46185 Fuel Filter Base with Baldwin BF 7633 fuel filter > 1/2 NPT to 1/2" barb > hose to engine
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