I've owned my Dodge for over 4 years now, and have upgraded the lift pump, which is the raptor 100 gph on the side of the block, edge ez, 4 inch exhaust, and I believe it has at least 60hp injectors that were installed by the previous owner. I am at 400 rwhp now, tested at the hunting for horse power up in cda. My question that I am asking, why is my fuel pressure dropping down 5psi at WOT? I have spent many hours trying to find information on this, and its hard to get a definite answer. the Diesel mechanic I take my truck to says its normal, but I know its not, especially since my truck will start to stutter if I let off the pedal after stomping into it for to long( by no means do I drive the truck aggressive, I drive it like an old man, like my old man lol)  I want to upgrade my fuel lines to half inch from the tank to the lift pump, including fittings. but when I look online, I'm only finding the big line kit from the filter to the injection pump. Any advice would be much appreciated. I'm not looking to start a proper fuel psi forum, as I know its been beat to death.

 

15 psi at idle, 5 psi at WOT- doesn't seem normal. I'm on my second raptor 100gph -----this is my first post, let me know if I'm doing anything wrong.

Edited March 10, 20178 yr by Alexio Auditore

I fought this issue for along time...I replaced everything, went through 6 raptors.  I upgraded to a better pump and the issue was gone.

 

You can mount the pump on the frame, it will work better.

 

In the mean time bump your idle pressure to 20 psi.

Thank you. So what type of pump did you upgrade to and did you keep the stock size fuel lines through out? did it come with the things to mount it to the frame?    I'm debating on upgrading from edge ez to the comp box, but I think ill wait till I get the fuel pressure thing resolved.

I ended up with a fp125 through pureflow directly.

 

 

I changed all likes from OEM to 1/2" trying to solve my pressure drop issues, but I never saw results.

 

 

what pressure do you see with the new pump now? could the 100gph just not be enough for the power I'm putting out?

18-19 idle 16 wot.

 

The ratings on the pumps are "hopeful"

ok. ill start pricing things out then, ill come back and post the results when its done. thanks for the help.

I would say stuff a fass 150 on it with 1/2in lines and call it a day. 

do the half inch lines come with it? fittings and all from tank to pump?

 I removed intank screens put the Rapter 100 on the frame with 1/2'' lines all the way and a 1/2'' draw straw. Removed cylindrical shaped plastic fuel filter in the fuel module that has screens and f/p is at 19 idle and 15 WOT going uphill with a load. Eric at Vulcan performance, now called performance supply has the best deals and best parts for the big line kit. Even his 90 degree angle going into the injection pump is a longer sweep 90.

 

Run around town with your fuel fill cap loose to see if you have a tank venting/ vacuum problem. If you do.... best to find a vented fuel cap.

Edited March 10, 20178 yr by JAG1

Yes, it comes with the 1/2in lines. You'll have to add a draw straw or something to that effect for sucking out of the tank as well. It's an expensive setup, but killing your injection pump is very expensive. 

 

Oh and welcome to the forum!  

It should come complete with all you need. Very much like the AD kits. Look them up on line and it will tell you what it comes with.

thanks for the replies. ill take a look at performance supplies and see what I can find. I think I ordered a 3/8 line from the filter to the injection pump last year from Vulcan, but that didn't make a difference. I have 234000 on the stock ip pump, I want it to last as long as possible for sure.

It is hard to get the big line kit to do anything when you are still pulling fuel thru the stock lines.

34 minutes ago, dripley said:

It is hard to get the big line kit to do anything when you are still pulling fuel thru the stock lines.

 

Make sure you replace everything inlcuding the pickup tube in the fuel tank. When I first got my AirDog 11 years ago I was in a hurry to go up North to see a friend in the hospital so I installed it against my stock pickup assembly. Needless to say it ruined the AirDog 150 ability to pump fuel and keep stable fuel pressure. You much have 1/2" lines from the tank to the VP44. You may keep you stock fuel heater and filter without any impact to fuel pressure or flow. 

is the pick up tube different from the draw straw? if so, do I need to get a bigger one then?    I was also curious if the fuel lines between the lift pump and injection pump should keep pressure after the truck is shut off? no problems with hard starts what so ever, but I notice there is no pressure that the gauge is picking up just before I start the truck?    Maybe I should replace the fuel return valve just because, though I understand they don't go out often?      

As for the fuel lines, are the quick connect ones any good or should I just stick with the normal push lock ones?

 

Sorry about the overflow of questions, I want to know all I can about this before I tackle this project in the spring.

2 hours ago, Alexio Auditore said:

is the pick up tube different from the draw straw? if so, do I need to get a bigger one then?    I was also curious if the fuel lines between the lift pump and injection pump should keep pressure after the truck is shut off? no problems with hard starts what so ever, but I notice there is no pressure that the gauge is picking up just before I start the truck?    Maybe I should replace the fuel return valve just because, though I understand they don't go out often?      

As for the fuel lines, are the quick connect ones any good or should I just stick with the normal push lock ones?

 

Sorry about the overflow of questions, I want to know all I can about this before I tackle this project in the spring.

The OE pick up tube is only 5/16 I believe. You can get the draw straw up to 1/2", might all be 1/2".

When you shut the truck all pressure bleeds off almost immediately. While the overflows can go bad it is not common as far as I know.

I have a AD with quick disconnects and I have not had any issues with mine, but it does seem that many others have had problems. If mine ever start giving me problems I will change them out for push locks. A little harder to install but pretty fool proof.

Dont worry about the questions. The only dumb is the one you dont ask. We all have some experience with that one. 

When I modified my fuel basket and put draw straw 5 from Vulcan in some lines are 5/16 but ID is more like 1/4 if you don't want psi swings you realy need to do all lines in 1/2 including return from lift pump, which ever one you chose, whether it's to filler neck ot to basket. I like mine to basket as it's keeping it full,  but maybe more heat to vp, I usually don't run tank less than 1/4 anyway. For more than one reason. 

Draw straw 5 will only work on strain baskets just so you know, but you can do quite a bit with jic fittings, that's what I did with return from my fass to basket. 

Edited March 12, 20178 yr by Dieselfuture

I know its been a while, but I am going to pull the trigger on the fuel upgrade system. (Finally) The good ol raptor with its wonderful reliability and stable fuel pressure is giving me problems, go figure. fuel pressure is slipping since it was put on a year ago, so I bumped up to 18-19 and crusing speed is around 14 to 15, but as I was driving off the job site yesterday, I looked down at the fp gauge and it was pegged out at 25psi!!!! so I shut the truck off and restarted it and back to normal?

DO NOT BUY A RAPTOR IF YOUR LOOKING FOR A LIFT PUMP! These things suck! ( and not fuel wise either)

 

anyway, so instead of using the warranty for another replacement of garbage, I'm am leaning toward the FASS that has been previously mentioned. but here is the questions.......

 

---What type of FASS should I get?( Titanium?) Heard airdog stuff isn't what it used to be

---How about GPH? 100 or 150? I'm running 400 hp but maybe someday 450 to 500....MAYBE( tbh, I'm leaning toward the mpg gains so might be looking into the quad that you guys have been using for a while. My edge EZ is giving me problems)

---The FASS comes with filters right? so should I bypass the stock filter on the side of the block or should I run it through and have dual filtration?

---Are the filters a special order you can only get online or at any autoparts store?

--- ill frame mount the pump, out of the way of debris damage path, is there a kit I need to get in order to mount it?

---I'm upgrading the fuel line to 1/2" including a drawstraw from Vulcan( one without return fitting), I was leaning toward the return line on the FASS to go to the filler neck, what do I need to get and cut and clamp, etc. in order to do this?

----Should the return line from the vp44 be upgraded to 1/2" line too?

 

I'm sure there are questions I'm forgetting, but for now, here they are. Thanks.

You could have my 11 year old AirDog 150 pump that has held 15 to 17 PSI the whole time.

that's awesome. but what about the new airdogs? Ive read a lot of negatives about them over the past five years, but then again, opinions are opinions I guess