Looking for experience with fuel lines and PSI

[015point9]

Currently have all fuel lines removed from fuel tank to VP44.  The lines that are inside the fuel module are 3/8 in size (about 8 inches worth)?   All other lines to VP44 are  ½ inch.   So just the line inside the fuel module are 3/8. 

Before I took the Air dog pump off , was at 21psi at idle using Vulcan pressure gauge.  Unsure about fuel PSI in actual use, just at idle, before I took it apart . (Also going to install pressure gauge)

How much do you think or guess a 8 inches of 3/8 line inside fuel module will affect PSI at VP44.

 

The reason I don't want to change out smaller fitting now is because the fitting in top on module has been  glued in and don't want to take chance of breaking the thing.

Edited April 23, 2017 by 015point9

[Dieselfuture]

If it worked before I'd leave it alone, unless you're planning on making big power. As long as you didn't have 1/4 or 1/3  tank issues where if you slammed breaks or took off to fast and lost pressure, you should be fine. Factory basket is reduced to 1/4 id, 3/8 is way better. Or you can modify your basket to all 1/2 or buy one already done. You will have a slight flactuation in psi but should be minimal for DD. It's WOT is where it may drop more. 

[Mopar1973Man]

10 hours ago, 015point9 said:

Before I took the Air dog pump off , was at 21psi at idle using Vulcan pressure gauge.  Unsure about fuel PSI in actual use, just at idle, before I took it apart . (Also going to install pressure gauge)

 

 

Need to know what your WOT pressure is like. This is the most important number.

[015point9]

4 hours ago, Mopar1973Man said:

 

Need to know what your WOT pressure is like. This is the most important number.

 

Op here...and not a very experienced OP

Agree 100%  Operator error on my part!

After getting gauge and new fittings from Vulcan I wasn't sure of best way to have portable gauge hooked up and be able to drive around to get WOT pressure.   Thing about it later I should of duck taped it to windshield and drove around to get WOT reading.

14 hours ago, Dieselfuture said:

If it worked before I'd leave it alone, unless you're planning on making big power. As long as you didn't have 1/4 or 1/3  tank issues where if you slammed breaks or took off to fast and lost pressure, you should be fine. Factory basket is reduced to 1/4 id, 3/8 is way better. Or you can modify your basket to all 1/2 or buy one already done. You will have a slight flactuation in psi but should be minimal for DD. It's WOT is where it may drop more. 

I'm not making any big power.  Yes, when fuel was being sucked from fuel module with a FASS pump was hooked up to it, everything worked OK.  When the FASS fell apart  60,000 miles, the (now X mechanic) installed an AirDog said "it was best to go with a draw straw" and then the next day after he couldn't get it to work, so he installed a sump.  Then two months later the sump was leaking, so I'm in process of getting the sump leak free going back to sucking fuel from fuel module. 

 

Sure been a challenge for me not knowing anything.  This fuel system has been only thing to go wrong since I've got it in 2005.  Before the fuel system fell apart,  never had it  to a shop in 11 years of me owning it for any mechanical failure.  Sure has been making up for lost time lately

 

This web site has sure been very helpful to me. I've sure learned a lot.

Thanks for all the help.

Edited April 23, 2017 by 015point9

[notlimah]

If I were you and had the whole thing apart already and the money to do it, I'd make sure all my lines were 1/2in just to be done with it and never have to worry again. I'd also go with a Liberty module from Vulcan.

[dripley]

My truck has a 3/8" pickup in it. I have about a 3 psi drop from idle to WOT. That is what my AD came with so I installed it. y pressure runs 18 at idle and 15 at WOT. It really am not worried about it but it does probably make the pump work harder. Knowing what I know today I would have taken everything to 1/2". Maybe one dayI will change it !!

[Mopar1973Man]

I'm running 1/2 inch lines and have very little drop like 1 to 2 PSI drop from idle to WOT. More noticeable in the cold winter months it can be more like 5 PSI.

[Haggar]

The inlet strainer on the pump is a bigger restriction to flow than the difference between 3/8" and 1/2" lines....  (my charts show a standard loss across a strainer of about 1.0 psi at 2 gpm on water...)

 

I ran a quick calculation: the pressure drop of a foot of 3/8 steel tubing at 90gph is 0.1 psi.  (for everything the same but 1/2" line, it is 0.06psi drop)   Since it is on the suction side, and you have not reached the limits of the NPSH for the pump, and we are withdrawing from a vented tank,  it won't affect the output pressure at all.  

 

I reran using a rougher pipe inner surface and increased the flow to 140gph.  it went to 0.2 psi  pressure drop.  I think its ok to use 3/8" suction side....

HTH
 

Hag

[notlimah]

So pulling fuel through that stock strainer in the basket creates that much restriction? I have my strainer in the bottom of the basket as per Eric's recommendation to leave it, but I've never seen pressure below 16psi so I'm not going to start fooling with it now, but definitely good to know.

[JAG1]

Did you guys pull the fine screen out of your Raptor lift pumps in let side? I sure did don't want a problem I cannot find. . What are they thinking anyhow? The right set up has a prefilter... always been that way too. I also pulled the basket screen and drilled the sides.

Edited May 11, 2017 by JAG1

[Evan]

I did draw straw and 1/2 to filter. Then saw 2psi on rease at idle when going 1/2" from filter to injection pump. That us with pressure gauge on elbo going into injection 

[notlimah]

4 hours ago, JAG1 said:

Did you guys pull the fine screen out of your Raptor lift pumps in let side? I sure did don't want a problem I cannot find. . What are they thinking anyhow? The right set up has a prefilter... always been that way too. I also pulled the basket screen and drilled the sides.

 

I didn't take out anything from the raptor pump on my 99. It's just in the stock location with big line kit to the VP and that's it. I do get a fairly drastic fuel pressure swing but it's too be expected given the setup.

 

On the 02 and the FASS 150, again nothing removed from the lift pump and I'm running the 1/2in auction line straight into my modified fuel basket with the drawstraw 5, no screens removed but I did drill holes. I see 17-19psi occasionally 16psi when cold, that's it.

[JAG1]

Your 02 and my 02 act about the same with about the same set ups. Just wish I can get the 01 to behave/ stop going to 25 psi. At least I've stopped the constant pendulum action on the gauge by changing filters.

[015point9]

Op here...  maybe wrong but I'm planning on leaving my fuel strainer intact. My basket worked many years with return line dumping into it.  My thinking is enough fuel is getting into basket to keep 

[notlimah]

2 hours ago, 015point9 said:

Op here...  maybe wrong but I'm planning on leaving my fuel strainer intact. My basket worked many years with return line dumping into it.  My thinking is enough fuel is getting into basket to keep 

 

You shouldn't have issues leaving it. That's what JAG and I were discussing. Some people prefer to remove them, others leave them. Both seem to have very similar results, and if there are differences, they're way to minor to worry about IMO. I run the stock strainers in my stock fuel basket with a FASS 150 and drawstraw 5 system and have had zero issues pertaining to the strainer.