Engine/Transmission (1998.5 - 2002) Fuel Pressure Question

[JDriscoll]

I just installed a fuel pressure guage on my 02 ram. At idle, the guage reads 8 psi, and driving down the road with no load, at 2000 rpms my guage reads about 5psi. If I accelerate hard, the fuel pressure drops to about 3 psi. The lift pump is only a month or two old. My question is should I be concerned with the numbers I'm seeing, they seem low to me. Is there anything I might have messed up when I installed the guage that would cause the low readings? Thanks for any advice.

 

[rjrkihap]

Hi;



My second lift pump was bad right out of the box. Within a week I was seeing figures like you're seeing. Unless you have a plugged filter or a gauge not hooked up correctly (loose wiring, poor ground) I think you need a new lift pump.



Good Luck



Ron

 

[VHolloway]

I have the fass II at idle 20 psi and wo 17psi

 

[JDriscoll]

Is there any way to test the lift pump other than replacing it?

 

[rjrkihap]

A gauge is a pretty good indicator of pump function. Monitoring over time will reveal if the pump is starting to fail. Mine have either gradually decreased in pressure over several months or they would drastically drop instantly and then return to normal pressure (eventually staying at the lower pressure).



Don't try to judge a pumps function by sound. Mine have always continued to run even when they were pumping 0 fuel.



Good Luck



Ron

 

[SHobbs]

If you have not done it yet. Relocate the L. P to the frame, toss the banjos go to AN fittings and loose the tiny line between the filter housing and the VP44 with 3/8" lines. Would also suggest utilizing the Vulcan draw straw as well. I have not done the draw straw, yet. The other suggestions have given me nearly 2lbs more at idle which currently is at 12psi and I can't get it below 8psi at WOT.

 

[jhoughton]

If you have an isolator that is filled with anti freeze it is possible the rubber baffel is actually beyond half way point when not running. I had this happen and through trial and error I finally found it and once properly positioned and filled I had proper fuel pressure indicating. You can try this or also get another test gauge and compare to your installed gauge. Hope this helps also as stated above the relocation and draw straw helps greatly. I have had great pressure with the install of the FASS. Absolutley no complaints. Idle 16-17 WOT 14 psi.

 

[JKinney]

How old is the fuel filter, it might be gettting plugged. The pick up screen in the tank also might be starting to plug. There are quite a few aftermarket fuel systems. Time to start reading and figure out which way would be best for you...

 

[isb360]

A lot of good advice here. Many of us have gotten dud LP's right out of the box or ones that die of infant mortality. Your upgrades will depend on your available budget, but unfortunately a permanent solution does require a bit of investment. I kept telling myself that I could never replace enough LP's to justify a FASS or a FASS HPFP, but when my 4th LP died, I threw in the towel and got the HPFP as well as the Vulcan draw straw.



There was a vendor called Wildcat Diesel based in NW Canada that sold a "max flow" fuel kit that put big lines in the engine compartment and did away with the banjos in favor of AN fittings. The upside was MUCH reduced pressure loss at WOT, but the downside was the increased difficulty in changing the LP due to stiff lines and big AN fittings.



When I eventually went to the HPFP, I ended up ditching 2/3 of the maxflow kit, so that was money down the drain, but the AN's remained which was good.



Relocate pump to rail or go with aftermarket near-tank-mounted pump and larger fuel lines... . Vulcan draw straw if you want to drop the tank, and you'll be good to go.



Tim

 

[rjrkihap]

Tim;



I've heard/read quite a bit about the draw straws. Are you having any troubles going below 1/2 tank of fuel? Are there any other issues with the draw straws?



Thanks



Ron



ps. I second absolutely moving the lift pump (which ever one you choose) to the frame rail. I still do not understand why Cummins placed an electric pump that far away from the tank and on an engine that vibrates as much as our do.

 

[JKinney]

Tim;



I've heard/read quite a bit about the draw straws. Are you having any troubles going below 1/2 tank of fuel? Are there any other issues with the draw straws?



Thanks



Ron



ps. I second absolutely moving the lift pump (which ever one you choose) to the frame rail. I still do not understand why Cummins placed an electric pump that far away from the tank and on an engine that vibrates as much as our do.

I might have had trouble once going below a 1/4, but I was also dealing with a plugged filter at that time. I have a personal rule to refill when i hit 1/4 on a positive note fuel is needed to cool the vp44, so one should not run till empty anyway.



I wasted money moving the lift pump. some of it is still on some is in a box.



I even got a couple of used oem pumps laying out on the garage floor.

 

[Seafood10]

I had the same issue and opted for a Glacier pump mounted on the rail and don't even think about checking my fuel press. ever again. I went through a couple of the stock Carter pumps and am now completely please with my 20 psi at idle and 15-17 psi at WOT.

 

[JKinney]

I had the same issue and opted for a Glacier pump mounted on the rail and don't even think about checking my fuel press. ever again. I went through a couple of the stock Carter pumps and am now completely please with my 20 psi at idle and 15-17 psi at WOT.

Ditto on the Glacier. I also enjoy pulling the relay and jumping the pins to prime the system after a filter change.

 

[azpete]

Just recieved the Glacier mechanical pump. Will have to find some time to install it and see how that works out.

 

[KFranco]

JDriscoll.

If you don't see any leaks in the fuel lines particularly where you tapped for the gauge then I don't see any reason why your gauge is faulty. It appears to work since it fluctuates in PSI readings when at idle versus wot. Your wot number of 3psi is slightly below what most would like to see of 5psi. Knowing the inherent problems of lift pumps on these trucks I would make the investment for an aftermarket pump. That pump depends on what type of mods you are going to make. You will need to do some research on that. Most aftermarket pumps should allow you to make modest horsepower improvements.



Now as far as testing the lift pump you could always splice into the line between the lp and ip with a mechanical fuel gauge and keep it tucked away under the hood like I have. However I don't feel this is necessary in your case unless you really want to. Anyway, best of luck to ya

 

[isb360]

Tim;



I've heard/read quite a bit about the draw straws. Are you having any troubles going below 1/2 tank of fuel? Are there any other issues with the draw straws?



Thanks



Ron

Ron,

I haven't had any trouble with the tank going (dangerously!) low, although I am a bit nervous about it, having modified the system. The only tricky thing about the Draw Straw is correctly measuring the length of the main fuel pickup tube in the module. I forget the numbers, but I believe you want it 1/4" off the bottom of the module and cut at an angle instead of parallel with the bottom of the module. This maximizes the amount of fuel you can use in your tank -- this should be nearly all of the available fuel -- and also allows easy suction without restriction. What makes it tricky is that the pickup tube delivered by Vulcan is very stiff and obviously comes off of a large roll, so it is bent into a gentle arc shape. You really won't be able to "straighten" it out after install, so doing a fit-up with the slightly arc'd tube and estimating the cut location that way is the way to go. If you straighten it out for purposes of cutting, it will relax into its arc'd shape and be too far up off of the floor, thus rendering the last bit of fuel (1/8 tank??) unrecoverable for use in the engine.

Just go slow and careful and you'll be fine.



Tim

 

[JDriscoll]

First of thanks for all the advice. I replaced the fuel filter at the same time I installed the guage, so it is not a problem. I ran the truck all weekend (300 miles or so) and I didn't see any signs of leaks or any changes in the fuel pressure readings that I stated in my first post. My next step will be to use another guage before the isolator to verify what my guage is telling me. I do think relocating the lift pump would be a good idea. What kind of expense would I be looking at for an aftermarket pump (Glacier or a Fass system)? Thanks.

John

 

[KFranco]

I think I paid $380 for my glacier system. I don't even think they sell my system anymore... that is the 391 system.

 

[rjrkihap]

Thanks for the advice Tim. Sounds like a good option for my truck.



Ron

 

[ed9824v]

well that was exactly what my replaced lift pump was doing replaced with an AirDog with 1/2" lines and air water separator and filter lots of bucks but do not want to keep dealing with this. ED