Engine/Transmission (1998.5 - 2002) FASS-Airdog-RASP

[Jerky]

I was wondering if the RASP removes air from the fuel like the FASS and Airdog claim to do. Some of the comments have stated that the FASS and Airdog have changed the idle noise and have smoothed out the idle as well. Trying to make up my mind as the way to go. Maybe just a pusher setup. Thanks for your input. - Dean

 

[snowracer69]

RASP has no system to remove air. It runs in parallel to the stock system, leaving your stock LP in place for priming and for the potential of a belt breaking.



The RASP is a mechanical system while the others are electrical... . that is all the input you need, right there.

 

[Augie]

RASP has no system to remove air. It runs in parallel to the stock system, leaving your stock LP in place for priming and for the potential of a belt breaking.



The RASP is a mechanical system while the others are electrical... . that is all the input you need, right there.

If your belt should break the LP is actuated as back up via Hobs switch. I carry a spare belt for the RASP and serpentine since all belts have a potentional for breaking. I will take that chance in return for steady consistant fuel pressure since LP's and FASS have a potential for electrical failure. With RASP plus your LP, you have mechanical and electrical means of feeding the VP-44.

 

[paulb]

I like my RASP. It is well built, has redundancy, supplies plenty of volume, and is quiet. Anybody want to buy a fuel pressure gauge?



Paul

 

[24V-DSL]

One of the side benefits of the RASP for me is that I was able to build a woodstove fire with all of the posts I had printed off of the TDR over the past 2+ years on various pusher systems, pump options, etc. I had literally spent double digit hours on the TDR reading/printing trying to figure out what I was going to do.



Like Paul, I also can concentrate more watching the road instead of my fuel pressure guage.

 

[jmolnar]

Love My Air Dog. Lots Of Volume And Pressure, And Quiet Too. My Old Carter Pusher Pump Would Whine Like Crazy.

 

[Double J]

Anybody want to buy a fuel pressure gauge?



Paul

:-laf ..... no doubt.

 

[jmolnar]

Wonder Who Has The Most Mileage On A Rasp? See How It Holds Up Against The Air Dog. Just Because Dodge Puts On A Lousy Lp Doesn,t Mean Somebody Like Preporator Can,t Build A Nice Electric Pump. Most Car Pumps Last At Least 100k.

 

[paulb]

Wonder Who Has The Most Mileage On A Rasp? See How It Holds Up Against The Air Dog. Just Because Dodge Puts On A Lousy Lp Doesn,t Mean Somebody Like Preporator Can,t Build A Nice Electric Pump. Most Car Pumps Last At Least 100k.

I probably don't have the most, but I have about 20K on mine. If you've ever seen one (I just had to take my pump apart! ), besides the belt, there just isn't anything to break. Only time will tell for sure though...



Paul

 

[jmolnar]

Jerky, Bought Air Dog Because Of Bigger Fuel Line, Quality Fittings, Easy Install. Plus Never Heard Of Any Problems With The Air Dog As Compared To Fass. I Believe Worth The Extra Cash. John.

 

[Ncostello]

Kondolay showed me the RASP at Muncie. He explained how they purposefully fan the belt with the pulleys completely out of alignment in an attempt to fling it off or destroy it. I believe he said the belt handled the situation fine without breaking.



I'd say breaking a belt is extremely rare in almost any circumstance unless there is a serious mechanical failure or lockup.

 

[paulb]

I'd say breaking a belt is extremely rare in almost any circumstance unless there is a serious mechanical failure or lockup.

I agree. It's a cog belt, so no tension, and the rating on the belt is way more then the pump would ever require. KO engineering did an awesome job on making the brackets. I have less then . 5 degree deflection between the two pulleys on my pickup. I wish I could get it that close on the race car!



Paul

 

[OPoole]

At 3,000rpm you have no worries of belt problems. A big plus with the RASP is pressure goes UP!! with rpm not down. Also where its mounted it stays clean, RASP also carries a 5 year warranty

 

[Tcolesanti]

jmolnar,

Jerky, Bought Air Dog Because Of Bigger Fuel Line, Quality Fittings, Easy Install. Plus Never Heard Of Any Problems With The Air Dog As Compared To Fass. I Believe Worth The Extra Cash. John.





That's because the Air Dog has'nt been out nearly as long as the FASS.

 

[tractorface]

Supply restriction

None of these products address the problem with the fuel modules. Certain modules are worse than others which explains why some have problems and others don't. I suspect that the harder the unit sucks the worse the problems are. I would be surprised if some Air Dogs don't start showing up with failures due to this restriction. I would expect the mechanical RASP to handle this better and may not "show" the problem. Either way eliminating the screen/valve assembly in the module is a good first step.

That's my story and I'm stickin to it.

 

[TMills]

This sort of has to do with the other fuel posts, but what is the purpose of the fuel module? Does it just suck fuel from the bottom of the tank and have the fuel level sending unit on it?

 

[Ncostello]

My 99 had the all plastic module. I gutted it (screen, valve) and it did not help my relocated OEM pump... FWIW.



The module is a prefilter of sorts... and also acts as a makeshift fuel reservoir that holds a decent quantity of fuel. If a low tank level is encountered and fuel swashes away from the inlet at the bottom... . the fuel thats in the reservoir flows back into the tank... and consequently floods the inlet in the process which keeps you from sucking air. That was my take on it when I studied its design.



Just as a note... at 1/4 tank it would be very hard to have fuel swash completely away from the inlet unless you hit a brick wall or went up or down an extremely steep grade. We rocked my truck back and forth when it had a 1/4 tank and had the fuel really moving big time. It never came close to leaving the inlet point at the bottom of the tank completely.

 

[tractorface]

Yep

It is a bucket that floats up and down with the fuel in the tank. The "pickup" tube is housed within as is the VP44 return line. The fuel gauge is mounted to the side of this bucket. There is a fine screen assembly and a small diaphram type valve inside. Can not pinpoint the reason for the valve. Anyway there is another float valve on the bottom of the bucket that lets fuel in but does not let it out. I suppose this elaborate mess was designed to let a person run the fuel in the tank as low as possible and try to eliminate potential water in fuel issues as well as act like a strainer for the lift pump. Now the returning of Hot fuel to this bucket is a bad idea. By the way the return is positioned I suspect it is used to "pressure" clean the screen assembly as well as keep the bucket full. Now remember your VP does not want to see fuel above say 140 or so max. You have about a quart of fuel with hot fuel returning to it all the time. Under hard duty cycle the problem gets worse (hotter). The suction line barely keeps up with the stock lift pump needs. As the rubber diaphram ages it may begin to suck closed than release causing a pulseing action . This diaphram is similar to what you would find in a Briggs and Stratton lawn mower engine. Anyway I suspect that the amount of restriction from module to module varies greatly. I have tested my old unit with my stock LP and saw the pulsing with my own eyes. One could measure this restriction with a vacuum gauge. If you are really curious install a vacumm gauge on the supply side of the pump and take readings, than pull the 3/8 line running to the tank module and take readings with the line in a bucket of diesel. You will see a big difference. Now take an Air Dog or Fass and use it to suck fuel from the stock module, the diaphram will suck closed and really make the pump work hard. (Some guys talk about how loud the pump is) Removing the restriction will make the pump purr like a kitten. This is not rocket science just basic stuff. I wish I had not thrown my stock module away. It would have been nice to use it to show what I am talking about. My new "module" uses a 1/2" suction pipe with very little restriction. I think 1/2" may be overkill but... ... .



Anyway no need for the stock module if you use high capacity fuel filters and a high capacity water seperator such as on the FASS or AirDog. You could also use Racors or something as well. This does add restriction so nice High capacity units are important. Anyway I am really surprised none of the pump people are publishing maximum restriction data for warranty on thier units.



Hope this helps.



Think about it, why do VP44's work fine in other applications? Do you really think Carter builds that bad of a pump?

 

[Ncostello]

I for one think Carter actually makes that bad of a pump. We've replaced them on F650's ISB trucks here at work just as Dodge owners do. And we've had VP's taken out on the same trucks.



On ISC's the Carter pump only runs for 30 seconds at the start up. Then it shuts off and the CAPS injection pump pulls the fuel from then on. Thus the Carter lasts for a long time since it only runs briefly each day. Its main function on these engines is initial start priming and priming a new spin on filter. Thats my take on the Carters. They are not continuous duty pumps in my opinion.

 

[Mad Bomber]

Tank

Neil, that screen is really fine. When I dropped my tank this summer the fuel would not drain out of screen I waited for about 1 min So I dumped it out and cut out all the screens. Fass is now almost totally silent.