I have posted a colored cut away drawing of our fuel pump for any that might be interested. It is the last image at the below link. Later! Frank


http://f1.pg.photos.yahoo.com/ph/rm11234/album?.dir=/2fd4

Hey, Frank. I thought the pump was a recipricating pump. (runs back and fourth, not rotary)

Nice pic, but a little small. Do you have a larger version? I can host it if Yahoo has a size limit.


Also, it looks like you took a really good look at the filter head. What are your thoughts on the inlet check valve from the tank? Do you think it is restrictive or unneccessary. I am not talking about the white ball.

Amric, I had a 4.2 MB photo to start with but I couldn't get it in my album. How can I get it to you? The area under the check valves is a lot smaller than 1/2". I am sure it is big enough for the majority of us. The guys running the big numbers might have a flow problem. Every restriction in the system adds a little to the total suction head. I am sure GM knew exactly how much the filter adds to the system. We do know that we can add too much because some have had to add lift/prime pumps to prevent cavitation/aeration. The check valves are needed to prime the filters and probably to keep the line from the filter to the pump full of fuel to insure a fast start. That is what the white ball does when the filter is removed. Later! Frank

Max, the pistons are reciprocating. The cam in the center is pushing the plunger in and the springs are returning them. Radial piston pumps or engines usually have a connecting rod attached to a crank shaft. A lot of hoist air motors work this way also. Later! Frank

What is the purpose of the gear pump in the upper picture, or is this a picture of a totally different pump?

The gear pump is attached to the rear of the High pressure section through a common shaft. The gear pump is not a positive displacement pump. As a matter of fact you can pour fuel in the inlet and watch it run out of the exit. This is the reason you must prime the fuel system with the pump on the fuel filter! If the gear pump section was a positive displacement type pump the motor could self prime but it would take cranking the engine for awhile. The purpose of the gear pump (low pressure) is to draw the fuel from the tank through the filter and deliver the fuel under pressure to the high pressure section of the pump. It uses the pressure from this pump to control the high pressure output of the high pressure pump. I have the entire pump apart on my work bench and can answer all questions of how it works as I've traced the entire circut out. For High Hp applications the addition of a lift pump to help supply the gear pump is a must.

Now this is good stuff and it applies to my new truck as well. Thanks guys!!!!!

Diesel tech,


I know this is a strecth but could you visulize any method for air to escape? We all know that air builds where there is a higher pressure like on the incoming side of a fuel filter. We also understand air rises to the top of a system. With those two concepts in mind, could air be returned to the tank?


I wish I could be there to see the pump. Are you going to the DHRA race May 1rst? If you brought the pump and other componets , that would be my final straw. I would have no chioce but to drive down to Kentucky!http://www.dieselplace.com/forum/smileys/Approve.gif

So how high of psi can the lift pump supply? If they are identical, the cummins guys are pushing over 15-18psi with lift pumps. Is this ok on the gear pump? Seems to be.

Has the Cp3 pump actually not been able to supply enough fuel to the rail yet?(with a lift pump). Any cooling issues when using high amounts of fuel?

Thanks

I remeber reading a MOTOR AGE article ( courtesy of HOOT) that stated the low pressure pump would sufffer physical damage with any input pressure greater than 20 PSI.

From the Cummins Cutaway pics in the Cummins section

http://www.dieselplace.com/forum/uploads/Z2A_DSCN4759.jpg

All gears pumps are positive displacement. The fuel is simply runing around the outside of the gears just like when it is turning. Diesel Tech, there a good training course on the GM site that shows a cut away of the pump running that you might find interesting. Later! Frank


Maybe I should elaborate on the above statement before someone gets their shorts in a bunce. A positive displacement pump delivers a fixed volume of fluid for every revolution of the pump. To do this it must have a constant supply of fuel to the pump inlet to prevent cavitation. This pump was not designed to pull fuel from and empty line all the way to the tank. You can change the total output of the pump by varying the speed . The output volume of our pump is constantly changing with the engine speed. Thus it is a positive displacement varible speed pump. I was lucky enough to see the animation run. I am sure there is a good reason why Bosch chose to mount the pumps together but I am not going to speculate on that. I hope the spelling is good in this post. I am without my spell checked today. Later! Frank Edited by: Frank Blum

hoot,


D Tech said high horsepower applications, not sure that would apply. No doubt about the engine, but anything south...........http://www.dieselplace.com/forum/smileys/Big Smile.gif j/k

Here is a link to Frank's picture for those who want to see it in higher resolution


http://www.ntinnovations.com/Pictures/DuramaxPump.jpg

Warning on use of lift pumps.......If supply pressure is too high you will blow past the fuel filter o ring.O ring was designed for suction not pressure...

Welcome GMworldclassmaster. Glad to have yet another tech. on board!http://www.dieselplace.com/forum/smileys/Approve.gif


Steve

I don't have a clue what the positive and negative pressure ratings of the OEM filter are. For a list price of $600+ it should be good! I do know that the Racor 645/660/690 Models may be located on the suction or pressure side of the fuel transfer pump. They are rated 40 PSI max under the hood and 60 PSI for a chassis mount. I would be real surprised if the rest of the popular brands weren't the same. Same here on having another Tech on the forum. Later! Frank Edited by: Frank Blum

The low pressure side of the pump will allow fuel to go through it with the gears in a stationary position! A positive displacement pump doesn't do this( at least all the one's I've worked with). The pump will move a fixed volume of fuel when properly supplied but by changing what is supplied you change what will come out. Since it will allow fuel through to the control solonoid everything works out fine. The control solonoid let's the necessary fuel to the high pressure side and the rest is sent to the center section to lubracate the interworking and then be returned to the tank. So adding a lift pump to supply the low pressure side just allows the pump to supply more fuel to the high pressure side when needed. This solves the pressure drops we have seen when running high Hp engines. I see no area designed to remove air from the fuel. The fuel travels from the front Aluim. plate through the center casting to the rear mounted low pressure pump on the bottom. The outlet is on the top of the gears where the fuel travels back into the center casting and goes to the front aluim. plate and up to the control soloniod. This passage also feeds into the center of the high pressure pump to lubracate the shaft, bearings and high pressure pistions. Excess fuel goes from here to the return line. The fuel that is let through the control valve feeds to the top of each high pressure pistion where there are two valves and a high pressure bleed/check valve on each pistion. When the pistion travels down the cylinder is filled by sucking the intake valve open and the low pressure fuel fills the cylinder. Once the pistion starts up the bore the valve closes and pressure begins to build. Once the pressure rises above the outlet check valve opening pressure fuel travels out to the common rail. To control the high pressure Bosch uses a bucking regulator valve that's part of the intake valve assemble. The low pressure holds this assemble in place as the pistion travels up the bore. If the pressure becomes to high the intake assemble moves up and allows the fuel to be returned into the intake area instead of going out the port to the common rail. A very simple but effective way to control high pressure with low pressure.


Two things need to be address when adding a lift pump. How much power are you going to add and how much pressure will the fuel system take. Right now we are OK with 5 - 7 psi on the system. The Dodge boys run 15 - 19 but they donot have the fuel going through the EDU like the D-max does. We tested the EDU at 5 psi for 30 days non stop with no leaks. We have raised the pressure to 10 psi and are rerunning the test to see if any leaks start. Once the test completes we will run a High Hp truck at 5 psi then rerun at 10 psi to see if there are any changes. That will let us know what we need to do. If your not going over 400 RwHp you really donot need the lift pump unless you have added a post OEM fuel filter

I have only rebuilt/disassembled a couple hundred pumps in my short 40 year career so I will bow out to superior knowledge. Later! Frank Edited by: Frank Blum

Frank and Dtech,


Thanks for the knowledge! I am still completly baffled that the dogge runs the exact same lowpressure/highpressure pumn and also a rearward electric lift pump. ( correct me if I am wrong). WTH? did, GM hose us again? Probally the culprit of many GM Dmax specific problems?Edited by: Bronco

Bronco,


As Steve has said (and i've seen the bosch book myself) the fuel system calls for a lift pump. its right there in the diagram. so i would gather gm did short us a lift pump, at least according to design. obviously it works fine without it unless we greatly exceed the spec'd horsepower/torque ratings for our engine.

GMworldclassmaster, what dealer you at?

A gear pump is a positive displacement pump. Stop it from turning and you will not pull through it well.





By adding a lift pump, we are compensating for the inefficiencies of the pump in question, and head loss/pressure drop (increase in negative pressure required to induce flow) across the system. These losses are there regardless of filter placement as pre or post OE.





As for the OE filter oring blowing out, I highly doubt it. It is pretty well captured inboard of the rim of the filter can. I've seen these systems run at excessive psi w/o leakage or damage. I do not recommend it, but I've seen it take whatever a non regulated (installed bass-ackwards) Holley Red can deliver without any problem.

Distinctive "RED" logo.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Flows 97 GPH (free flow).
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Flows 71 GPH at 4 PSI.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Maximum pressure is 7 PSI.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Regulator is not required.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Motor draws only 2 Amps current.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif 7-1/2 Amp fuse recommended.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Provides constant fuel flow with no pulsation.
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FuelPump_pics/RedBllt.gif Has externally accessible pressure relief valve (max. 7 PSI).

When wired and plumbed backwards it does not relieve pressure and runs until the pump motor stalls.





The owner wired backwards and when it did not work, reasoned that it was mis-marked so he replumbed.

The benifits of adding a lift pump for post OEM filter mounts has been well documented. The problem comes from the post OEM filter traping air and causeing the low pressure pump to lose its prime. Once it loses prime the engine will nolonger start or run until the consumer reprimes the system. The question is why is the post OEM filter doing this, and to date no one has the answer for sure. Some believe its removeing air from the fuel but if that's true why does it not do it with a lift pump? This has only occured with a post OEM filter install. None of the pre OEM filters have had this problem.

The evidence of air already exists at the OE filter. It discolors from bottom to top, except when pressurized and no air is present.





It is my belief that the reduced pressure (vacuum) combined with increasing temperature (radiant from engine and heat sink from EDU) pushes the fuel to, or near to the vapor point in normal operation.

It is my belief that the reduced pressure (vacuum) combined with increasing temperature (radiant from engine and heat sink from EDU) pushes the fuel to, or near to the vapor point in normal operation.





The Heat sink from the EDU is already there in the stock configuration so there is no change before and after, the problem doesnot happen stock. So if what your saying is that the post OEM filter is heat sinking more temperature causeing the fuel to reach vapor point...... Then it's time to move the new filter as heat also brakes down the ability of the fuel to properly lubracate the injectors and injection pump!

The presence of air is evident in the OE fuel filter on otherwise stock trucks. Every OE filter that I've seen cut open at an early age shows the banding described above.





Try an air trap between the EDU and OE filter on a stock non lifted truck, and I'm quite sure you'll find air. We've seen people remove the quick connects, and inspect all of the lines only to find the air keeps coming. Putting the fuel under pressure keeps the filters full and the housings air free. This holds true for my truck even running a lift pump that crosses to 12-15"hg under hard accelleration.





The fuel gets it's heat from the valley and the EDU. If anything, the secondary filter acts as a heat sink to dissipate heat from the fuel when mounted below the airbox tray.

Kennedy


Below are quotes from your two post that say the opposite from one another!


"It is my belief that the reduced pressure (vacuum) combined with increasing temperature (radiant from engine and heat sink from EDU) pushes the fuel to, or near to the vapor point in normal operation. "


"The fuel gets it's heat from the valley and the EDU. If anything, the secondary filter acts as a heat sink to dissipate heat from the fuel when mounted below the airbox tray."


Since the fuel path across the valley and through the EDU do not change between stock and a post OEM filter install and a stock vehicle starts just fine your statements just don't add up. It's very obivious that the addition of a post OEM filter causes the no start problems. The pressure drop should be the same for a post OEM install Vs. a pre OEM install so that's not it! What's not obvious is why it does it. You've done nothing to answer the reason why.

Location and volume...

Diesel Tech,


Maybe you should take Frank Blum and Kennedy up on that gear pump training. Maybe clarification of pump efficiencies would also help. Gear pumps are POSITIVE displacement. Simple as that. Recip. Diaphragm and many other pos disp pumps will allow flow through the pump by off seating valves. Does that mean they loose their classification as a pos disp pump. I don't think so. With your claims of past experience with pumps this should be easy. Thats why efficiency factors are used in pumps when volumes are critical. As pumps age they also loose their efficiency. (more slippage due to wear occurs)


As far as how free vapors form in our fuel system your statement that no one knows for sure should only apply to yourself because some of us that already completed the leg work and ran the numbers do in fact know. Its no secret to most that have been keeping up with the threads in the past. Lets not take a step backwards over settled issues. A simple calculation based on temp/pressure should so the trick for ya. Or maybe a simple review of past threads. You also could use clarification on the differences between the forming of vapors verses the trapping. What's really scarry is that your posts are primarily derived from speculation and should have more merit before it is provided to the public. Lots of people take the information they gather here at face value.Edited by: a bear

DeletedEdited by: a bear

Did Abear get a message for being to personal torwards Dtech? Or is it only JK that gets special protection? How much is the weekly rate for protection? I could start offering a side service as well. http://www.dieselplace.com/forum/smileys/Clown.gif


Seriously though Abear,Jk, Chuntang, Jpblock you all have a simialr school of thought. You tie air into temperature so on and so forth.


The only affect tempeature has is the following. Hot fuel holds less air than cold fuel. Hot fuel can be cavitated more than cold fuel. It is a double edged sword with no perfect scenario. Hot fuel and cold fuel have there pros and cons.


Air is always in the fuel. The amount depends on fuel temperature and sloshing and exact chemical makeup of the particular fuel you are using.


What causes air to come out of the fuel? Vacum, pressure difference (such as moving across a chosen filter media) and also fuel being allowed to settle.


How this separated air will manifest itself is completly dependant apon where it was separated and what paths it was given to reside or travel too, once separated.


The original intent of this thread was to illustrate the physical makeup of the Bosch two stage factory fuel pump. Inbetween the pictures given early in this thread and the lengthy verbal dscription given by DTech, I am grateful.


It is becoming obvious that the Gm low pressure lift pump cannot self prime. Without the sealed system and factory hand pump, the low pump would never pickup a prime. It is also becoming obvious that if the high side pump demand is ever greater than the lowside pump supply, the diagnostic software will show a difference inbetween the desired and actuall rail pressure.


Terminology is only one factor in the bigger picture.http://www.dieselplace.com/forum/smileys/Geek.gifEdited by: Bronco

wow.......that's tough.


This has been a great read! The only thing I missed is someone saying something about volume vs. PSI. I'm guessing that abundant volume supply with low pressure is better than low volume with high pressure, supplying the fuel pump. er.... It's better to have a 1" line @ 3 lbs feeding the pump than a 1/4" line @ 15 lbs, right? And this positive pump, while emmersed in fuel it will always have (+) prime with varring pressure from RPM,right?





Burner------------> http://www.dieselplace.com/forum/smileys/Big Smile.gif

Burner,


Could not have said it any better.Edited by: Bronco

It seams some people here already feel as though they have all the answers so maybe they can explain why the Mega filter assembly from Kennedy has to use a lift pump inorder to work when all other pre OEM filter assembles donot. Same trucks, same engines, same fuel path up until the filter installation.


Mega filter = no start and must reprime system over and over or add lift pump to hide problem.


Others Filter kits = work fine no reprimes.


So I guess what there trying to say is the installation of the Kennedy Mega filter causes the fuel to get hotter and out gas more............

What really happens is the Mega filter media is the right amount of resistance in relation to flow so that air builds up around the nipple. When the system is shut off, the air rises to the gear pump and causes a loss of prime. The JK solution of drilling the nipple as to allow air to not accumalate around the nipple is a good solution however at the expense of very small amounts of single pass fuel being fed to the engine. The lift pump alleviates this problem as well.


Another side affect could be as soon as enough air builds around the outside of the nipple, it will drop down and flow with the fuel to the low pressure pump. Then the air bubble will either go back to the tank via the return line or into the common rail via the high side pump. Whether the common rail recompresses this air bubble or not is out of my scope.Edited by: Bronco

Location (last in line before the LP pump), Volume (filter size/fuel retention time)= increased vapor separation time., Head design (extended thread engaugement nipple).

John's filter is not the only one that had a problem with a no start condition. Mitchagain, for one, had a Cat mounted under the air box that did the same thing. He moved it to the second alternator position and the problem went away. I think a couple others had Racors under the air box without problems. Diesel Tech, the ground work and most of the testing was done over on the diesel page. That is where most of the data can be found. There are a few points and some termology that we all don't agree on but quite a few of us have the basic hydraulics down pat. Later! Frank http://www.dieselplace.com/forum/smileys/Big Smile.gif

<DIV>Diesel Tech</DIV>
<DIV>This Link to Baldwin I think holds the answers to a lot of the questions. The air is removed from the Fuel by the 2 micron filters under a vacum.</DIV>
<DIV>A lift pump puts enought pressure on the fuel to get it throught the filter without the air being removed.</DIV>
<DIV> </DIV>
<DIV>http://www.baldwinfilter.com/engineer/pdf/94-6r.pdf. </DIV>

John's filter is not the only one that had a problem with a no start condition. Mitchagain, for one, had a Cat mounted under the air box that did the same thing. He moved it to the second alternator position and the problem went away. I think a couple others had Racors under the air box without problems. Diesel Tech, the ground work and most of the testing was done over on the diesel page. That is where most of the data can be found. There are a few points and some termology that we all don't agree on but quite a few of us have the basic hydraulics down pat. Later! Frank http://www.dieselplace.com/forum/smileys/Big Smile.gif





Yup,





Location, and volume. Add media density as well.





Hoot, Victory Red, and a few others also had no starts with other mfr filters.


I haven't heard of it for a while, but a few guys even had trouble with the OE unit...

Kennedy,


Just so you know, I have never had any no starts with the OEM. The few that did probally had a dirty filter or a loose filter.


I understand your filter has had a few issues, which really does not bother me as much as it use to. As long as you work with the consumer, either by a full refund or free lift pump, well then no big deal. http://www.dieselplace.com/forum/smileys/Cool.gif


BTW, it is not just media " density" . There are several different types of media being used currently. Synthetic media, cellulose and several differnet brand names " stratapore" " microgalss" ect. ect.


Certain filter medias respond to certain pressure/flow rates by forcing the air to separate. The media has to match the flow rate and then you create a natural phenomenom. It is just laws of physics. http://www.dieselplace.com/forum/smileys/Geek.gif


JK your a rocket scientist and did not even know it. LOL. You just need to add an air bleeder to the filter head and then you would be in buisness. http://www.dieselplace.com/forum/smileys/Big Smile.gif

There IS a bleeder in the filter head, and it is in the highest point of the unit on the dirty side of the fuel. The pick up extends well into the filter creating a large area for air to collect. Once the fuel is pressurized (adding a lift pump) we no longer collect air.





Media density (term used loosely like the word air) can factor in as in the bulletin mentioned above. Media density, surface tension of the fuel across this media etc.





The element that I use has multiple times more surface are than about any other commonly being used, so as to minimize pressure drop across the media, and slow down the flow rate per square inch.

I hope we aren't starting the fuel filter wars all over again. We have a lot of choices for secondary filtration, use what you are comfortable with and stop jabbing the vendors.


I use the mega with a lift pump and am happy with it. There weren't as many choices when I purchased the mega. Today, I would still pick the mega, I want the maximum filtration I can get. I would add a lift pump no matter what secondary filter I used. Lift pumps are a good thing IMHO.

John's filter is not the only one that had a problem with a no start condition. Mitchagain, for one, had a Cat mounted under the air box that did the same thing. He moved it to the second alternator position and the problem went away. I think a couple others had Racors under the air box without problems. Diesel Tech, the ground work and most of the testing was done over on the diesel page. That is where most of the data can be found. There are a few points and some termology that we all don't agree on but quite a few of us have the basic hydraulics down pat. Later! Frank &lt;IMG id=chkImg1 onmouseover="this.style.cursor='hand'" onmouseout="this.style.cursor=''" alt="Click on image to open in new window" src="smileys/Big Smile.gif" name=chkImg2&gt;





Yup,





Location, and volume. Add media density as well.





Hoot, Victory Red, and a few others also had no starts with other mfr filters.


I haven't heard of it for a while, but a few guys even had trouble with the OE unit...

I never EVER had a no start with my post OEM Racor. It performed flawlessly for over 40,000 miles and two filter changes up until I traded in the truck.

No problem .... just wanted to clear that up. I was running the 90hp Juice and it always kicked butt so I didn't notice any supply issues either.

My mistake. Somebody did a Racor under the tray and had an issue. Forget who now...

I have been comparing the OEM filter on the bench with the Racor 660. It is like night and day. If I keep my truck to 100K the first thing that will go is the OEM filter. I would bet money that this filter adds more to the suction head than the rest of the system combined. Later! Frank

Is there an adapter/bypass available for those with a secondary filter? Or would you just remove and plumb out the OEM?

I have been comparing the OEM filter on the bench with the Racor 660. It is like night and day. If I keep my truck to 100K the first thing that will go is the OEM filter. I would bet money that this filter adds more to the suction head than the rest of the system combined. Later! Frank


I am planning this same thing, but I'm not going to be able to wait for the warranty to run out. I would like to run both a 690T and 690S on the frame rail, and completly bypassing the OEM. The only problem will be priming and bleeding air from the system.

Amric, you might want to reconsider putting both filters on the rail. The OEM is close to the pump for a reason. That being to keep the line from the filter to the LP pump full of fuel for a quick start. Later! Frank

I have been comparing the OEM filter on the bench with the Racor 660. It is like night and day. If I keep my truck to 100K the first thing that will go is the OEM filter. I would bet money that this filter adds more to the suction head than the rest of the system combined. Later! Frank


Probably why GM is going to a longer OEM filter. This rather smallish filter combined with a 15K change interval seems to be pushing the limit. I also keep in the back of my mind what I may do after hitting 100K. With these quickly evolving filtering ideas I will be looking at the latest and greatest when the time comes. http://www.dieselplace.com/forum/smileys/Approve.gif

I have been comparing the OEM filter on the bench with the Racor 660. It is like night and day. If I keep my truck to 100K the first thing that will go is the OEM filter. I would bet money that this filter adds more to the suction head than the rest of the system combined. Later! Frank


Probably why GM is going to a longer OEM filter. This rather smallish filter combined with a 15K change interval seems to be pushing the limit. I also keep in the back of my mind what I may do after hitting 100K. With these quickly evolving filtering ideas I will be looking at the latest and greatest when the time comes. http://www.dieselplace.com/forum/smileys/Approve.gif

Not to mention the physical limitations of a small filter. There had to be a compromise in flow/filtration/change intervals in the design process to use a filter media that small.

I just ordered a filter pack from Genos Garage for my Dodge. For $100 shipped I get 4 stratopore oil filters, 2 fuel filters and an air filter.

When I get the filters I'll takes some photos and we can compare what Dodge is doing, to the Dmax system. The Dodge fuel filters are a drop in, not a self contained spin on. No worries about rust. I believe the lift pump is built into this thing. I'm also considering additional filtration soon.

http://www.dieselplace.com/forum/uploads/C73_DSCN4766.jpgEdited by: hoot

Hoot,


Is that a cutaway of the Dodge filter ? The new 6.0 PSD also has a primary and secondary setup w/ drop in elements. Doesn't say anything about the secondary being high efficiency though. I assume it is. I may later consider a permanent setup with a drop in element to replace the OEM. Looks like a good option.

Amric, you might want to reconsider putting both filters on the rail. The OEM is close to the pump for a reason. That being to keep the line from the filter to the LP pump full of fuel for a quick start. Later! Frank


I'm thinking a lift pump could solve this issue and the priming issue at the same time.

Hoot,


Is that a cutaway of the Dodge filter ? The new 6.0 PSD also has a primary and secondary setup w/ drop in elements. Doesn't say anything about the secondary being high efficiency though. I assume it is. I may later consider a permanent setup with a drop in element to replace the OEM. Looks like a good option.

Yes that's the Dodge unit.

are the fuel filters for the CR Cummins more or less expensive than the Duramax fuel filter?

are the fuel filters for the CR Cummins more or less expensive than the Duramax fuel filter?

$13.50

What is the recommended change interval for the Dodge filter.