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FASS DDRP: Why not????

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Some folk's are saying that this pump is fine for a stock motor, and some are saying it is only good for target practice or an expensive paper weight. It is my understanding that it comes with two different springs (to adjust for more pressure if desired) , that it is a relatively easy install in the oem position, and that it is an option to install it down on the frame close to the tank with the required relocation kit. It comes with a four year warranty from the same folks that make the higher end FASS systems. So, for a stock motor, why not use this pump? Thank's for your time and attention............Hood Latch

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  • Author

Is the fuel filter a new filter? A restricted fuel filter can cause low pressure like this.

Live Oak, No, it is not new. I must of had a brain fart or something cause I did'nt think of that, whew!!! I have new filters here, I'll give that a try next. Thanks for the reminder. Hood Latch

I think you got it all hooked up correctly. From what I can dig up searching and looking at pictures and all anyways lol. If it's hooked into #1 thats the supply line so that would be right. Posted Image Yeah that pressure doesn't inspire me either :lol3:

I have mine hooked into the banjo at the return/outlet fitting of the VP44, should I maybe move it upstream to #1?

You can see it just below the sticker on the VP44.

http://forum.mopar1973man.com/attachment.php?attachmentid=439&stc=1&thumb=1&d=1263600058

Edited by flman

I didn't think you could get a pressure reading from a fuel line going back to the tank. I would most definitely move it to #1. If your getting normal pressure readings then maybe there is something I don't know about these things and their return system. Wait for someone else to confirm it..

  • Owner

Yeah it got to be on the line to the #1 in that pic... The return line is not going to see pressure unless you pumping excessive amounts like about 20 on the supply side... So switch it around...

Must be senility setting in? I did indeed have it on line 1 (IP Inlet) after all:confused:

14 PSI after cold fuel gets flowing for a few minutes, and 11 to 10 at WOT. I probably could have went with the 150 pump, but I read all kinds info here that too much fuel flow will make the fuel heat up. Any ways, after a hard run the VP44 pump body and computer on top is cool to the touch, not even luke warm. So I am probably just fine. Also, I do have that inaccurate isolator in the line ;)

Can you put glycerin on the gauge side of the isolator to make the gauge react better?

I bet money on the isolator is screwing up the reading I bet if you made a temporary connection directly you'll find a whole different set of numbers...

One day, I might just do that, but I wont obsess over it, by the time spring time comes, I am sure the gauge will start reading a higher number, once the fuel in the gauge line and isolator warms up.
  • Author

Finally made my choices for now, and here's how it went. My project proceeded as follows: 1st. I installed a new DiPricol mechanical fuel pressure gauge, and ran the line directly from the vp44 to the gauge without any device (snubber, needle valve, isolator, etc.) in between. I did this because I wanted p.s.i. readings from the stock carter lift pump and then the FASS DDRP lift pump without any interference from any inline device. 2nd. I installed a new FASS DDRP lift pump in the stock location on the side of the block. 3rd. I installed a new Baldwin fuel filter. 4th. I installed a new barrel type fuel pressure isolator between the vp44 and the gauge. I started and drove the truck after each step of the project, and recorded the p.s.i. readings on the new gauge. (1) Stock Carter lift pump --------------------------------------- 8 1/2 p.s.i. @ idle ----- 3 p.s.i. @ w.o.t. (2) New FASS DDRP ---------------------------------------------20 1/2 p.s.i. @ idle ----- 11 p.s.i. @ w.o.t. (3) Then install new Baldwin fuel filter ------------------------------ 22 p.s.i. @ idle ----- 13 p.s.i. @ w.o.t. (4) Last step: Install new barrel type fuel pressure isolator between vp44 and the gauge --------------- 20 1/2 p.s.i. @ idle ----- 12 p.s.i. @ w.o.t. (5) Interstate driving: 65m.p.h. @ 1750 r.p.m. with cruise control activated ------------------------------ 15 p.s.i. --to-- 17 1/2 p.s.i (6) Normal around the county type of driving ----------------------------------------------------------------- 14 p.s.i. --to-- 20 1/2 p.s.i. No doubt, the 10 p.s.i or so spread between idle and w.o.t. could possibly be contributed to the FASS DDRP being only a 40 g.p.h. pump, and the size of the stock fuel lines. Did I prove anyone right or wrong here? No, not at all. That was never my intention. I know far to little about this particular subject to try and prove anything. Do I think that I have found an adequate answer to my particular needs for my stock motor? Yes, I think so. Only time will tell, and if I have been wrong about my choice, I will say so and report it as such. Either way, I will have no one to blame nor praise, but myself. Thanks again, to all who have participated on this subject. Your time and attention is appreciated........ Hood Latch

Edited by Hood Latch

your still above 10 psi at all times!:thumbsup::thumbsup: so you have already help your vp44, compared to leaving that crappy carter pump. you are using the stock lines?

  • Author

your still above 10 psi at all times!:thumbsup::thumbsup: so you have already help your vp44, compared to leaving that crappy carter pump. you are using the stock lines?

Yes, I am using the stock plumbing. As I indicated, the FASS DDRP was installed @ the stock location on the side of the block.
  • Owner

Well that explains why the large pressure loss because of the DDRP volume limits plus the volume limits of the fuel lines and banjos. Still only seeing about 2 PSI fall from 17 @ idle and 15 @ WOT...So this points out the limitation of the plumbing and pump...

  • Author

Well that explains why the large pressure loss because of the DDRP volume limits plus the volume limits of the fuel lines and banjos. Still only seeing about 2 PSI fall from 17 @ idle and 15 @ WOT... So this points out the limitation of the plumbing and pump...

Mike: Yes, I agree. While I have no way of proving it @ this point, I too am thinking that it has to do with g.p.h. limitations of this pump and the somewhat restrictive size of the stock plumbing. As you, and others have pointed out before: Dodge/Cummins seems to have short cutted the fuel delivery systems on the 2nd. Gen's. As I have stated: If I ever think this pump is not providing what I need for my situation, or if I ever decide to do any horsepower upgrades, I will most certainly go to a higher g.p.h. pusher pump down next to the tank with big lines all the way to the vp44. Hood Latch

Where can I get a 1/2" hose kit, the 3/8 line shipped with my Fass 95 GPH may be lacking, and are any of you using the in-line filter before the Fass pump?

But what about the inline Napa filter that ships with the Fass, are you using it? Thanks for the Vulcan link.

my airdog didn't come with an inline filter, but i think the water separater acts as a prefilter. i did hook up the factory water sep/filter(so i would have fuel heater).i have 1/2" line from tank to VP44

my airdog didn't come with an inline filter, but i think the water separater acts as a prefilter. i did hook up the factory water sep/filter(so i would have fuel heater).i have 1/2" line from tank to VP44

This in-line filter is between the outlet of the fuel tank, and the inlet of the pump, it has nothing to do with the separator/filter. It just seems like a bad Idea to create a restriction like that before the pump?
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