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(3-10 GPH equals 20 to 6 MPG at 60 MPH)

I've given up trying to explain lift pumps and over-servicing filters to members here.

If Fass or Airdog ever came out with 1,600 gallon per hour, 400 psi pump, it would be their biggest seller.... hands down.

You want 2 psi of pressure at the CP 3 / CP4.2 inlet, under all operating conditions.

Anything more, is a sausage fest.....

Everything Whizzy described, points directly to the Kennedy centrifugal set up. Long life, low noise,high volume, low pressure, no returned fuel, no added heat, no foam.
 

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After I installed my lift pump, my stock filter head started to leak and found a small crack so I took it off and took the rest of the fuel line that I had left over from the FASS and deleted the filter head. Haven't looked back since.
That was certainly the cheap fix, and probably a good temporary solution.

It also will prevent you from priming the system in the event of a LP failure though. Just some food for thought.
 

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Pumping more fuel to the CP will not cause the CP to pump more to the engine. If it is desired to refilter the fuel more times it is necessary to provide a bleed back to the tank somewhere after the filters but before the CP. This has to be done with a pressure regulator that bleeds off excess fuel to maintain pressure. A regulator that simply blocks excess pressure will not help. I would do this but I wouldn't have an excessive capacity lift pump just for this purpose. I would depend on a 50 GPH pump to provide 3-10 GPH to the CP at 5 PSI and the other 40-47 GPH would go back to the tank for another pass. (3-10 GPH equals 6 to 20 MPG at 60 MPH, about what we typically get)

This is what I would/will do. If I am wrong then please tell me so. I might have missed something.
I agree with you completely.

It seems to me that is what the FASS 95 I have is doing. It does not have a mechanism to pre-heat the fuel prior to the WS Filter but since I live in the south I dont see that as an issue.

Rather than keep the stock filter on the stock head, and in an effort to provide the cleanest fuel possible to the CP and injectors, I have an adapter so I can run an Ultra High Efficiency filter in that location. CAT does not give the efficiency of those UHE filters except to say it is less than 4 microns.

I will soon be 20,000 miles on this setup and when I get there I will remove and cut open that UHE filter to see just what it did or did not catch, after getting through the two Baldwin filters on my LP.

When I do that I will post the results so others can see if I did some good for the CP and injectors or whether I wasted a bit of money. IF I did that, I will probably switch back to a stock filter on the stock filter head. Time will tell.
 

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Wow. Now I know why I joined these forums. The information you guys pass on is amazing. I appreciate all of the guidance people provide!

I'll have to read these posts a few times again to wrap my head around them fully, but hopefully I can keep the dirt & [email protected] out of my injectors and keep this puppy running strong!
 

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(3-10 GPH equals 20 to 6 MPG at 60 MPH)

I've given up trying to explain lift pumps and over-servicing filters to members here.

If Fass or Airdog ever came out with 1,600 gallon per hour, 400 psi pump, it would be their biggest seller.... hands down.

You want 2 psi of pressure at the CP 3 / CP4.2 inlet, under all operating conditions.

Anything more, is a sausage fest.....

Everything Whizzy described, points directly to the Kennedy centrifugal set up. Long life, low noise,high volume, low pressure, no returned fuel, no added heat, no foam.
I actually had two pump solutions in mind as I was writing. The Kennedy and several Carter options. I do believe that recirculating fuel can improve the amount of stuff filtered out but there is a practical limit to that. My Case backhoe has a filter that looks like a ball of cotton twine. If we could find that kind of filter then there would be improvement in the fuel quality with each pass, no matter how many passes were made. that type of filter catches contaminants by adsorption, meaning they stick to the fibers of the filter. The filters we have work by screening. Adsorption gets less per pass, something like 85%, but gets another 85% on each succeeding pass. Screen type filters can get as much as 98% on one pass but maybe only 5% more after the first pass. That's 5% of the remaining dirt per pass, not 5% of the original dirt. The diminishing of returns is pretty steep.

I agree with you completely.

It seems to me that is what the FASS 95 I have is doing. It does not have a mechanism to pre-heat the fuel prior to the WS Filter but since I live in the south I dont see that as an issue.

Rather than keep the stock filter on the stock head, and in an effort to provide the cleanest fuel possible to the CP and injectors, I have an adapter so I can run an Ultra High Efficiency filter in that location. CAT does not give the efficiency of those UHE filters except to say it is less than 4 microns.

I will soon be 20,000 miles on this setup and when I get there I will remove and cut open that UHE filter to see just what it did or did not catch, after getting through the two Baldwin filters on my LP.

When I do that I will post the results so others can see if I did some good for the CP and injectors or whether I wasted a bit of money. IF I did that, I will probably switch back to a stock filter on the stock filter head. Time will tell.
I would prefer to have a very high grade filter in the second position because it would greatly reduce the need to change the OEM filter that so many people find hard to get to. I've changed several of them from the top of the engine using the right tools and body positioning but it isn't easy. Ideally the OEM filter could become a lifetime device that didn't need servicing. I wouldn't trust to ideals though. I would just leave it there until the pressure gauge said it needed changing.

This is something of an optimized theory and other solutions will work for many of us, including just leaving it alone. There is no one right answer here.

Well, maybe one thing is for sure. The only good reason to have more than a 50 GPM pump is to refilter fuel. You are wasting money with a big pump and no way to return the fuel to the tank for refiltering.
 

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I would prefer to have a very high grade filter in the second position because it would greatly reduce the need to change the OEM filter that so many people find hard to get to. I've changed several of them from the top of the engine using the right tools and body positioning but it isn't easy. Ideally the OEM filter could become a lifetime device that didn't need servicing. I wouldn't trust to ideals though.

This is something of an optimized theory and other solutions will work for many of us, including just leaving it alone. There is no one right answer here.

Well, maybe one thing is for sure. The only good reason to have more than a 50 GPM pump is to refilter fuel. You are wasting money with a big pump and no way to return the fuel to the tank for refiltering.
I believe our thinking is very similar. My WS is also a 10 Micron filter. The Secondary is 4 Micron. The re-circulation of the fuel via the LP is one of the major reasons to have it, in my opinion. I realize that most is taken out on the first pass but every little bit more captured by the filters is that much less my CP and injectors dont have to deal with. Filters and oil, etc. are cheap; Engines and major components, not so much.

The CAT filter listed at less than 4 microns (possibly just hype, we will soon see) is there to try and catch even more that may have gotten past the 4 Micron filter. After 20,000 and I cut it open I will undoubtedly adjust the interval. If it really isn't catching anything I may be better off with a factory filter that has the WS separator function to catch H2O any that could have gotten past the Baldwin WS on my LP.

The jury is still out and I am still learning about these machines. Ive been shown to be incorrect in several of my beliefs and ideas so far on here, adding to the internal hard drive between my ears.
 

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Damn - should I be concerned using the Donaldson P553203? I bought that to replace my under the hood fuel filter and don't have a lift pump yet. If Donaldson isn't so great - should I look into a Racor filter instead?
 

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Sorry if you've provided this guidance before, but I thought the Donaldson filter was quite reputable for the LB7.

So if I look into the Racor fuel filter for under the hood, what would be my best bet for protection?
 

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I added a nictane adapter with the 1 micron microglass as the last filter after the AD 165. With that set up you wouldn't have to change the 1 micron for about 50,000 miles but its just added insurance.
I did the same thing.... I also added a filtermag on my airdog.

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Damn - should I be concerned using the Donaldson P553203? I bought that to replace my under the hood fuel filter and don't have a lift pump yet. If Donaldson isn't so great - should I look into a Racor filter instead?
At least your Donaldson that replaces the CAT filter has a water seperator and is 3 micron.
I wouldn’t get to excited about believing negitive comments on a filter and several other products 'uhNo that’s widely used and sold by several of our vendors.

https://dirtyhookerdiesel.com/i-14902333-donaldson-p553203-3-micron-fuel-filter-short-style-fass-titanium-replacement-fuel-filter.html

https://www.madjackdiesel.com/mobile/product.aspx?ProductCode=don-p553203&404;http://www.madjackdiesel.com:80/Donaldson-3-Mic-Water-Separator-Filter-p/don-p553203.htm=

If you want to go with Racor which is a 4 micron filter do it on the next filter change.

I have a AirDog 4G100 with WS and 5 micron filter Liftpump and Racor under the hood with the water seperator plug. I’m considering putting my WS back on plug it in so I’ll have a warning if water is ever present.
 
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Sorry if you've provided this guidance before, but I thought the Donaldson filter was quite reputable for the LB7.

So if I look into the Racor fuel filter for under the hood, what would be my best bet for protection?
Guidance is ignored quite often by people that know anything.
Opinions that only one brand LP is good and that’s what everyone should use nothing else.

Your fine with your filter choice.
Racor is a 4 micron filter the one thing you’d gain would be the water in fuel sensor.
 

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I was actually driving into work today, jumping onto my last small stretch of highway and I got into the throttle. Got second gear up to 2500 rpm and then boom. Nothing. Gas pedal had zero response. Rpms went right down to zero. I pulled off to the side of the road, tried to shut off and turn back on and couldn’t get it to turn over. I ended up having to take the Donaldson filter off, check all the seals and rings etc and put it back on. Primed the hell out of it and cranked it and after about 5-7 seconds it turned over. Weird instance but I drove a bunch more tonight with no issues


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After I installed my lift pump, my stock filter head started to leak and found a small crack so I took it off and took the rest of the fuel line that I had left over from the FASS and deleted the filter head. Haven't looked back since.
Your method will work...............UNTIL............The FASS pump motor quits and you lose prime.

At that time you will have no way to prime the system and you will be stuck, where ever you are.

Your truck will either be towed or sit right there until such time as you reinstall a factory filter head or repair the FASS pump motor.

My point is, it is probably not the optimal long term solution.
 

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I was actually driving into work today, jumping onto my last small stretch of highway and I got into the throttle. Got second gear up to 2500 rpm and then boom. Nothing. Gas pedal had zero response. Rpms went right down to zero. I pulled off to the side of the road, tried to shut off and turn back on and couldn’t get it to turn over. I ended up having to take the Donaldson filter off, check all the seals and rings etc and put it back on. Primed the hell out of it and cranked it and after about 5-7 seconds it turned over. Weird instance but I drove a bunch more tonight with no issues


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I'm thinking you may have a small air leak that normally isn't enough to matter but when you got on it and the fuel usage went up, because of higher than typical RPMs causing the CP to pump more, the suction on the intake increased enough to make the air leak important. You might try driving a bit with the transmission locked in a lower gear so that you have more RPMs and see if it makes a difference.
 

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Your method will work...............UNTIL............The FASS pump motor quits and you lose prime.

At that time you will have no way to prime the system and you will be stuck, where ever you are.

Your truck will either be towed or sit right there until such time as you reinstall a factory filter head or repair the FASS pump motor.

My point is, it is probably not the optimal long term solution.

Redundancy is a good thing if you can afford it. Having a primer pump isn't much of a cost and it could be really convenient some day. Ideally the CP will draw from the tank without help but even GM isn't that confident. From a certain perspective the lift pump is just a backup for the CP but not exactly.

In a pinch one could prime the fuel line by removing one end, blowing air into the filler opening and then reconnecting the fuel line while the fuel is spewing out. But that isn't the nicest way to get a prime. Every diesel I've ever owned has had a way to manually prime it. There is a reason.
 

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I'm thinking you may have a small air leak that normally isn't enough to matter but when you got on it and the fuel usage went up, because of higher than typical RPMs causing the CP to pump more, the suction on the intake increased enough to make the air leak important. You might try driving a bit with the transmission locked in a lower gear so that you have more RPMs and see if it makes a difference.


Worth looking into for sure. Since getting it to run again I’ve been romping on it on as many straight shots and on ramps as I can to see if I can duplicate it. Thus far, no luck. But if it does it again, I’ll follow up and try out your method. Although I hope the issue is dead and gone!


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