FASS DDRP: Why not????

[guesswho512]

This is sort of related to this thread; Can someone tell me what the inside diameter is of the stock metal fuel line that runs from the stock filter housing to the inlet of the vp44 ? Thanks .Hood Latch

i think they are 3/8s? but that is probably the OD. Edited January 28, 2010 by guesswho512
bad info

[Hood Latch]

i think they are 3/8s?

Thank's Guesswho 512. That's what I thought too, but I read somewhere that someone made mention of that particular line as having only a 1/4" I.D. I've never had one off to look at, but it would surprise me if it were only 1/4" I.D. Anyone else had a good look at one?

[edcasey]

The O.D. is 3/8 inch. It fits perfectly in a 3/8 inch I.D. hose. I read on one of the forums that the I.D. is .23 inches but can't confirm this.

[Mopar1973Man]

I had a local machinist measure mine at 6mm ID...

[flman]

In Plumbing 3/8" OD tubing is called 1/4". So yeah the wall thickness makes it smaller, steel tubing is probably a little thinner then copper tubing?

[edcasey]

I had a local machinist measure mine at 6mm ID...

Ya...that's .24 inches. Pretty restrictive.

[AH64ID]

On my 3rd gen I used 3/8" compression fittings for my filter setup, so it would seem to be the same size line. I wonder what would improve if I went 3/8" life from the tank to the OE filter. I already have 3/8" from the OE filter to the 2um, to the CP3.

[Mopar1973Man]

Ya...that's .24 inches. Pretty restrictive.

Too lazy to do the conversion for it... But thank for confirming...

[Hood Latch]

Too lazy to do the conversion for it... But thank for confirming...

Yes Sir: I think you will find that 6mm. converts to .243" actually smaller than 1/4". Whew!!! that is on the small side it seems.

[Mopar1973Man]

Ok.. 2 Cents to toss... :2cents:Now as for the pipe/hose ID will detrimine max volume rate of the fuel pump at set pressure. Like in real world example since I worked for a fire dept for 6 yeears it the best way to explain it. Now for the sake of the example the water pressure is going to be set at 80 PSI and equal pressure always. Now take you normal every day 1/2" ID garden hose and fight a house fire... I bet money your going to lose the house. But now some shows up and replaces you hose with a 1 1/2" hose still at 80 PSI and now he's got a fighting chance to save part of the house (more GPM). Now the crew shows up and you switch out for 2 1/2" hose and a partner to help you hold the line. Now the fire it going to be put out...Something with the Cummins fuel system. You got a pump that can put out 15 PSI but the lines are so small the demand exceeds the pump (stock pump and lines) usually shows up as large pressure drop. Now upgrade to 1/2" lines and good strong pump (even stock carter) and now only lose a few PSI from idle to WOT. This is because the pump and plumbing can keep up with the demand. But now change to RV275 and Edge Comp on 5x5 now that stock cater can keep up... so now a 100 ro 150 GPH pump is needed...But for rule of thumb Speed / MPG = GPH so if your traveling 55 MPH divide by 20 MPG should equal 2.75 GPH This is your engine demand rate.. WOT is a whole another ball game the most I see measured is rate around 20-30 GPH

[AH64ID]

Something with the Cummins fuel system. You got a pump that can put out 15 PSI but the lines are so small the demand exceeds the pump (stock pump and lines) usually shows up as large pressure drop. Now upgrade to 1/2" lines and good strong pump (even stock carter) and now only lose a few PSI from idle to WOT. This is because the pump and plumbing can keep up with the demand. But now change to RV275 and Edge Comp on 5x5 now that stock cater can keep up... so now a 100 ro 150 GPH pump is needed...

Except that the lift pump are setup for a flow, not a psi. So take a stock system and put a 1/2" hose on it, I would expect the psi to drop. At a fixed flow if you reduce the resistance the pressure will drop. It will increase flow a little, but the pump only flows xGPH.

But for rule of thumb Speed / MPG = GPH so if your traveling 55 MPH divide by 20 MPG should equal 2.75 GPH This is your engine demand rate.. WOT is a whole another ball game the most I see measured is rate around 20-30 GPH

The fuel filter on a 98-02 is rated at 23GPH, so I would presure your math on WOT is pretty close. The 3rd gen is rated at 60GPH.

[edcasey]

On my 3rd gen I used 3/8" compression fittings for my filter setup, so it would seem to be the same size line. I wonder what would improve if I went 3/8" life from the tank to the OE filter. I already have 3/8" from the OE filter to the 2um, to the CP3.

When I added the 2 um Cat filter and Baldwin F/S I switched all the fuel line to 3/8 including a 3/8 Dorman fitting from Vulcan using the stock pickup. My maximum fuel pressure stayed the same because I'm using a bypass regulator shimmed to 15.5 psi. Previously my fuel pressure would drop from 15.5 psi under light throttle to just over 12.5 psi WOT. I was surprised that after adding the filters and 3/8 fuel line it never dropped below 13.5 psi WOT. With the restriction of the two filters, I really expected the pressure to drop lower than before at WOT not stay higher. It seems the 3/8 line and Dorman fitting helped quite a bit with fuel flow. I've since removed the stock fuel canister and gained another .5 psi WOT. Now it never goes below 14 WOT.

[AH64ID]

When I added the 2 um Cat filter and Baldwin F/S I switched all the fuel line to 3/8 including a 3/8 Dorman fitting from Vulcan using the stock pickup. My maximum fuel pressure stayed the same because I'm using a bypass regulator shimmed to 15.5 psi. Previously my fuel pressure would drop from 15.5 psi under light throttle to just over 12.5 psi WOT. I was surprised that after adding the filters and 3/8 fuel line it never dropped below 13.5 psi WOT. With the restriction of the two filters, I really expected the pressure to drop lower than before at WOT not stay higher. It seems the 3/8 line and Dorman fitting helped quite a bit with fuel flow. I've since removed the stock fuel canister and gained another .5 psi WOT. Now it never goes below 14 WOT.

That makes sense as you run a bypass regulator.

[Hood Latch]

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

Now for the next step in this experiment; I am going to order a big line kit to run between the stock filter housing and the vp44. When I get it installed (probably in the next 7 to 10 days) I will add the results to list of readings above. I need to think about if I want a 3/8" kit or 1/2" kit. Any thoughts about that? (while keeping in mind that I am running a FASS DDRP in the stock location on the side of the block and stock lines from tank to DDRP) Also, I'm fairly sure that I am going to add an in-line filter (at some time) between tank and DDRP. Now I know that some of you folks might be scratchin' your heads right now saying, why did'nt this old knuckle head listen and just do one of the pusher pumps with big line kits to begin with? Well, I really am not too hard headed, sometimes I just like to experiment with (new to me) projects and document the evidence along the way as it presents it self. There is (at least to my way of thinking) a certain method to my madness. And as I have said before; If this DDRP experiment does not work out for me, than I have another good use for it. Now having said all that, I want to say this; I very much appreciate any and all comments, suggestions, and or experiences of others that they want to share and have already shared here on this thread. The responses have been more than I (as a new guy) thought they would be, and I have learned much. Thanks again, Hood Latch

[Mopar1973Man]

Now I know that some of you folks might be scratchin' your heads right now saying, why did'nt this old knuckle head listen and just do one of the pusher pumps with big line kits to begin with? Well, I really am not too hard headed, sometimes I just like to experiment with (new to me) projects and document the evidence along the way as it presents it self. There is (at least to my way of thinking) a certain method to my madness. And as I have said before; If this DDRP experiment does not work out for me, than I have another good use for it.

Well that's why I've not said a whole lot in this thread... I know you trying to learn from your experience and show the member your results of the testing. This is good. Yes I could of step in and feed you my results to my testing way back then... But why??? So if you willing to explore and test I'm not going to stop you. You just might find something I didn't...

[Hood Latch]

Well that's why I've not said a whole lot in this thread... I know you trying to learn from your experience and show the member your results of the testing. This is good. Yes I could of step in and feed you my results to my testing way back then... But why??? So if you willing to explore and test I'm not going to stop you. You just might find something I didn't...

Thank's MPM. I appreciate your patience, and most certainly your hard gained knowledge that you obviously are most willing to share with others. As for my finding something that you may have missed, well I kinda doubt that. Yeah, there is always some possibility I guess (however small it may be) that I might come up with some new value as to the question at hand here, but we will see. In the mean time, it is providing an interesting excersise for me, and I am enjoying the process. And I am certainly more than happy to share the results of my findings, however inconsequential they may turn out to be. Edited January 30, 2010 by Hood Latch

[Mopar1973Man]

There is a slight difference between our 2 runs... Mine was done with Vulcan Big Line kit and a Carter Campaign Pump and yours with be a FASS DDRP and Big Line Kit so I'm really curious if the FASS DDRP can reclaim its title some how with a few mods... :shrug:But stlill in all the common thing is still the DRRP is short in GPH rate, short in warranty, and long in price... So I knowi ts not exactly the best pick for a pump but there is a lot of them out there and maybe, just maybe you'll find the magic to make them work... Who knows... That's why I never will stop a person from trying something again even if its known for issues. Because maybe you'll see something that now one else didn't... (Prayin' for ya!)

[Hood Latch]

There is a slight difference between our 2 runs... Mine was done with Vulcan Big Line kit and a Carter Campaign Pump and yours with be a FASS DDRP and Big Line Kit so I'm really curious if the FASS DDRP can reclaim its title some how with a few mods... But stlill in all the common thing is still the DRRP is short in GPH rate, short in warranty, and long in price... So I knowi ts not exactly the best pick for a pump but there is a lot of them out there and maybe, just maybe you'll find the magic to make them work... Who knows... That's why I never will stop a person from trying something again even if its known for issues. Because maybe you'll see something that now one else didn't... (Prayin' for ya!)

Thank you, Sir.