Hi guys, New VP44 installed a week ago. I also have the raptor 100 mounted in the stock location with stork fuel lines. The pressure is dropping about 4-5 psi at wot and about 1.5-2 psi at cruising speed. I'm trying to avoid another vp44 replacement.....ever :banghead:. Would a vulcan big line kit be beneficial to me to help keep the pressure up? Thanks in advance for all replies, and thanks for the wealth of knowledge on this site. 2002 Ram 25005.9 Cummins

You never said what the pressure was at idle.....

Sorry. Should've given more detail. 12.5 at idle (I know that needs to come up)10 cruising7 at WOTi was also referring to the Vulcan kit from filter housing to pump.

Sorry. Should've given more detail. 12.5 at idle (I know that needs to come up) 10 cruising 7 at WOT i was also referring to the Vulcan kit from filter housing to pump.

You're already hurting your new VP44. Bump that up to 20 PSI, and don't let it drop below 14 PSI. And yes, a big line kit will help. Order it from Jamie at Cummins Performance Parts.

Sorry. Should've given more detail.

12.5 at idle (I know that needs to come up)

10 cruising

7 at WOT

i was also referring to the Vulcan kit from filter housing to pump.

Keep it in the green... (14-20 PSI is optimal)

Standard specs...

Yes. A Big Line Kit can flow up to 520 GPH compared to the stock lines (6mm ID) can only flow 75 GPH.

Big lines all the way is even better. I did that with a major improvement overall.

Thanks for all of the insight!!! I feel like I've done more research on this VP44 than I did in four years of college . I will get that kit and add it on ASAP. I'm currently checking pressure through an isolator and I'm not real sure about the accuracy. As soon as I get the big line kit i'm going to ditch that thing and go with the needle valve set up.Strange thing is that when the VP44 was replaced the truck was still struggling to run and throwing a P0230. The mechanic called the pump shop and they told him to turn the Raptor down to 10 PSI. Since then there has been no code or any problem (noticeable) from the truck. The pressure has been a concern for me though. Hopefully the big line kit and getting the pressure up a little will solve the mystery for me

When you say stock location, are you meaning right by the engine? Are you using the stock fuel filter? You also said you are using the stock fuel lines. Is that correct? If you are using the stock lines, the big line kit is not going to help you that much. The only way it would is if you run the same size line from the tank to the pumpand to the filter, then the big line kit! Correct me if I am wrong guys.

That is correct. Stock lines from tank to raptor pump in the stock lift pump location, 1/2" line from raptor to stock fuel filter canister (1/2" line came with raptor), then stock line from filter canister to VP44. I believe the raptor is rated for 100 gph, but not sure if t could do that with stock fuel lines from the tank.

You would have less of a psi drop if you have the same diameter hose from the tank to the vp, move the pump closer to the tank, then crank up the psi so it reads about 20 psi at idle.

Word of caution... I don't suggest going over 20 PSi. There is a lot of people reporting going 25-30 PSI without failure. But this is nearly double the stock pressure and is not needed. Once the overflow valve open the return line is limited on how much it can flow being its much smaller than the 1/2" big line so don't get carried away with your upper pressure limit.

Got big line from filter to vp44 with fuel pressure gauge.Idle - 17psi (in gear 17.5-18???)Cruising 55-70mph - 14-15psiWOT - 10psiWOT seems a little low to me, but are these numbers acceptable? I'm hoping they are ok, but if not, I'm considering the relocation kit. I've read the relocation kit is pretty straight froward. Cut supply line and run 3/8 to relocated pump, run 1/2 from pump to filter housing, then run wring harness. Anything else I'm not thinking about? Would you guys recommend the 1/2 or 3/8 relocation line (pump to filter). Just curious since i'm stock and running raptor 100.Thanks again!!!!!

Anyone who has taken the entire fuel system apart from tank to vp44 knows the greatest restriction to flow are the POS fittings Dodge used, some of which have ports or openings of just 1/8". If you removed all the stock fittings and replaced them and up sized to 3/8" ID hose it would remove almost all the pressure drop at WOT. This only applies if you are running through one filter. If you are running an after market pump/filter unit into the factory filter it will drop off 3-5psi at WOT. I run 2 filters (10 & 3 micron) because dirt is as big a killer as low flow. The 1/2" fuel line is overkill because no fitting going into the vp44 will give you the equivalent size/volume of flow. The system will only flow as much as the smallest restriction will allow. If you reuse any of the fuel pick-up line from the tank, you are also limited to the stock 5/16" OD stainless steel tubing, which again will only flow so much. If you install a draw straw, replace all the fittings and use 1/2" hose, you are still limited to the opening size for the fitting going into the vp44. If you doubt this, pull that fitting off and take a look. Even replacement fittings used for 1/2" JIC/pushloc still only have an opening of about 1/4" or less because the threaded port into the VP44 is only so big. I'm still on my original VP44 (knock on wood), and rarely add anything to my fuel. Installed a pump/filter unit at 6K miles and have ran the 10 & 3 micron filters and maintained at least 10 psi using the factory 5/16" fuel line from the tank to the pump, then 3/8" hose and new fittings all the way to the VP44. With 20psi at idle, I see a 5 psi drop when I stand on it. This pressure is measured directly at the inlet to the VP, not from the aftermarket pump which is where many people choose to connect their gauges. this doesn't take into account pressure drop throughout the reminder of the system. Hope all this helps and it's just my 2 cents based on personal experience. PS, the 3/8" hose is also a lot easier to work with and route.