FASS in a M923 with Cummins 250

[Vintage iron]

As a diesel mechanic I am always looking for ways to improve the way our trucks run. After I sold Stevepala a Cummins big cam 400 Last year. Steve told me about the benefits of a Fuel, Air, Separation, System. I did some homework and came up with some design flaws in The Cummins 250 fuel system. First of all our PT pump needs to suck the fuel from the tank through a restriction (the filter). This makes the pump work harder, causes cavitation in the pump and makes aerated fuel through air leaks. Adding a FASS will supply the PT pump with fuel that pressurized to 12PSI, free of air and filtered to 4 micron. By supplying clean and pressurized fuel to the PT pump we get higher pump pressure to the injectors and better injector spray pattern due to the pure fuel. My customer Greg pulled the trigger on adding a FASS on his M923 that runs on 1400R20 Michelin XZLs. His truck already ran great so I was not sure how much a FASS would increase the way his truck ran, but adding a FASS also protects the engine too.

Greg bought the FASS from distributor and after a few talks with the helpful techs at FASS I ordered the all of the fittings needed to install it. I ran all new Aeroquip feed and return lines to the FASS and the engine. Martin Cox helped my with the right place to tie into the truck wiring.

After the install the truck ran noticeably smoother and stronger. Hills that the truck would loose power on before, now you can power right up, Shifts are firmer and the truck wants to pull. Maybe Greg can give a better explanation of the improvement since it is his truck and he drives it all the time.

 

[swbradley1]

Interesting. Would the same thing work for an M813?

 

[Sephirothq]

Is the pump 24 volts?

 

[Elideclan2]

Mine is the truck with this fass fuel system in it. As Matt (vintage iron) said the truck runs noticabley smoother throughout its rev range. I also did quite a bit of research before making the purchase. My truck ran good before the filter install, so I was not expecting a performance advantage. I bought the system because of its reputation for removing air and water from the fuel system to prolong lifespan of the expensive bits in this old motor. The performance uptic was an added benefit.
In the coming weeks I will report on the performance of the unit.
thanks to Matt for a really clean perfessional install.

over and out.

 

[doghead]

One more question.

but adding a FASS also protects the engine too.

Protects it from what/how?

 

[patracy]

One more question.



Protects it from what/how?

Lack of fuel. Try unplugging the lift pump on a VP44 truck. It'll run, you won't even know there's a problem. Until you get a CEL with a P-0216 error and find out you need to buy a 1K injection pump. Also the filters likely are a higher micron rating than the stock filters. (I know cummins/dodge used a 30 micron, and if memory serves, the LDT/LDS used a similar micron rating, I'd speculate the NHC-250/8.3 trucks had a similar rating)

 

[Bolkbich]

The Fass system does work. I know of 5 different trucks that use it, and all are VERY happy with it. The over the road guys say they get better mileage ,the engine runs smoother and makes more power...not crazy power but it is a noticable difference. The local guys say the truck is much snappier from light to light and runs better. These 250 cummins were used in the 60's/70's after that nobody except the military would buy one (unless they were stuck in the stone age). The Fass is not cheap but the more archaic the fuel system the bigger the improvement.

 

[Gunzy]

Which FASS part # did you use?(ie flow rate) I have now become interested where FASS say 2-3 mpg increase on empty truck and your statements about performance increases.

 

[patracy]

While I've seen an improvement in engine running/performance. I never saw a measurable difference in mileage that great. (I did notice about a .5 mpg gain though)

 

[Vintage iron]

I did months of research here on SS and online. I developed a theory and then asked the techs at Pittsburgh power and FASS. Yes, everyone agreed that supplying pressurized fuel with out air and filtered to Pt pump will improve the way any diesel motor runs. The 8.3L cummins has a lift pump already so this will work on any Cummins 250 Swbradley and yes this is a 24V setup .

 

[swbradley1]

Let's say for a second that their marketing and research is correct, couldn't I just get an Airtex pump and plumb it and a filter and a separator in for a lot less money?

Seems to me that $200 is more palatable than $650 if you got the same results.

 

[goldneagle]

Let's say for a second that their marketing and research is correct, couldn't I just get an Airtex pump and plumb it and a filter and a separator in for a lot less money?

Seems to me that $200 is more palatable than $650 if you got the same results.

Now see you bring up a good point. Use the same idea but with cheaper component costs.

 

[Vintage iron]

I have done a lot of research into improving the Cummins 250. There are a lot of things I like about the Cummins 855 based motors. I am not the best writer and I always try to make my posts easy to read, so I am sorry if some of my statements seem confusing. I will try to clarify some of my earlier statements. first, all fuel has dissolved air in it. Engineers refer to any limitation to flow as a restriction, even a 90' bend is a restriction and effects flow. So yes even a clean filter is a restriction. even connection is a possible spot to develop an air leak, in a suction or siphon system it is hard to see that it is sucking air into the system and hard to find a leak. Cavitation is caused when a pump is pulling fuel from the tank through a restriction, the suction makes negative pressure which makes the dissolved air develop into bubbles. Since air can be compressed the intrusion of air lowers the pressure to the injectors and the air in the system effects the injector spray pattern negatively. By adding a Fuel, Air, Separator, System. F.A.S.S. and new fuel Feed lines, I have fixed some of the design flaws.
first, I limited the number of connections and used Aeroquip hose. This will help because there are less spots to develop air leaks, a fresh and strong hoses.
second, the FASS filters the fuel to 4 micron and removes the air from the Fuel. this helps with injector spray pattern and PT pump pressure to the injectors.
third, The FASS has a water separator in it. Diesel engines do not like water in the system.
fourth, the injector pump will last longer if it is only getting clean fuel.
fifth, the injector pump can do it's job better, if it doesn't have to work so hard to get the fuel from the tank.
sixth, Cummins was very conservative in it's pump pressure settings. A mild increase in pump pressure will not put the Cummins 250 over it designed thresholds.

I hope this helped answer some questions. I tried to write things out as clear as I could. I want to thank everyone for their support and interest in my posts.

 

[porkysplace]

The hoses are a simple maintenance issue , which will solve all of the other issues on there own

 

[swbradley1]

The model for the 855 Cummins requires an oil pressure switch so that leaves out doing it with cheaper parts I guess. $697 for the FASS unit.

 

[silverstate55]

Let's say for a second that their marketing and research is correct, couldn't I just get an Airtex pump and plumb it and a filter and a separator in for a lot less money? Seems to me that $200 is more palatable than $650 if you got the same results.

Flow rate. The FASS can be had in basically 2 versions: the 95gpm and the 150gpm. I've been running the 150gpm on one of my truck for about 5 years now, and I love it. You can get FASS filters down to 2 micron, that is what I use on my FASS-150.

Also, the FASS has superior filtration built right into the unit, where an Airtex typically relies on add-on filtration. With a FASS, you can install 2 spin-on filters, one of which will incorporate a fuel-water separator and filtration down to 2 micron.

 

[doghead]

Matt, Thanks for talking with me on the phone.

You cleared up a lot of things.

I appreciate that, and your advice.

 

[Vintage iron]

Thank you for your comments Ron. Yes, there is no substitute for good maintenance. A FASS in not a solution for everyone, but it does have noticeable benefits. On your question about where the air comes from, Well a momma air and a Daddy air get together. LOL! No seriously, All fuel has dissolved air in it and it gets mixed in from sloshing around in the tank too.

I always try to work within a customers budget and build a system to suit their needs. Yes, having a lift pump and better filter would be a good option too. There is more than one way to skin a cat.

Greg and I are looking at the dual fuel line modification like Ptracy did a thread on and a better flowing air filter set up that I seen on Youtube. So there will be more to come on this project.

 

[PureMayhem]

Does the fuel go through the pump before or after the filters?

 

[tims931a2]

Is there a certain part number or info to give to FASS to order one of these setups? Might have to look into it in the near future.