ProPerDoper

How much flow is enough?

My 02 3500 24v has a stock Carter lift pump, and is running fine. No...I don't have a fuel pressure gauge, so I don't know exactly what it's doing. I do want to replace it for reliability reasons.

Mods on the truck are minimal: CAI, Magnaflow exhaust, Edge Tuner running at Heavy Trailer setting. I pull an 8000 lb. fifth wheel, and performance is awesome. Very satisfied.

After all the research and discussion with local diesel shops, I like the Alliant model given the actual reports of reliability from local shops, and the bypass feature. I don't believe that I need 100 gph of flow based on my setup, and just today after asking all over the place I got a response from an eBay seller stating that the Alliant is 50 gph as compared to stock at 40 gph.

So what I'd really like to know is:

Can anyone personally vouch with miles of use on one of the Alliant pumps?

How much flow is enough, given the mods that I've detailed above?

Thanks for any constructive guidance....

Lary Ellis (Top)

I think you would be better off just putting on a fuel gauge so you KNOW your IP isn't being starved for fuel and add some more flow with some 1/2" fuel lines. Then when the Carter goes down you can just replace it again.

Swapping from the Carter to the Alliant isn't going to give you anything UNLESS the Carter is already bad. Big fuel lines will increase flow and the Gauge will give you piece of mind and possibly save you $2000 in IP repairs.

ProPerDoper

Thanks for the perspective Lary. Not sure I looked at it that way.

I'm assuming then by your post that when the Carter starts to go, it's not a catastrophic failure mode and I'd have some time to get it off the road and repaired? That I could see a progressive decline in fuel pressure over some time period which would give me an indication?

The fact that the Alliant has a bypass gave me the impression that it was designed as a safety measure in case of immediate failure, and so I assumed this was the common mode. If I learned of any significant risk of this, I guess I could always carry a spare Alliant pump.

Any recommendation on a good value for the 1/2" line kit and a gauge kit? Name brand isn't as important to me as reliability and value.

Thanks again for the direction....

cougar

You need to hook up a pressure gauge, even if it is just a test gauge. You need to have 14-15psi at idle. You never want to see less than 8psi at WOT. You also want to shoot for no less than 90gph fuel flow. The VP uses excess fuel to cool its self. Any more or less than the pressures given above and you risk damaging the pump. These number came from a person I know and trust who overhaules these pumps and has seen both sides of the fuel pressure argument.

Danderson

I had the GDP relocation kit on my '98.5. Cummins had a barn sale at the time offering stock Carter's for $53.00 ea. I bought two but never needed them. I kept the tools and a spare pump with me for the $53/30 minute swapout.
A Westach fp guage from Geno's completed the conversion.

supr

I have noy heard of the Alliant pump.
The #1 problem of Gen 2 is dead Carter lift pumps. They seem to be pure junk, although some have lasted well, while others are dead out of the box. I would guess 20k may be an average.
At any rate, GET the FP gauge, so you know what you got. The Big line kit is a good idea, because it moves the LP down by the tank, thus making it easier to change.
Do a search on repacement LP and do a lot of reading. You can spend a lot of money on a lift pump, but they all fail. I chose the less expensive route and went with an AirTex. They give better FP and are OEM replacement. It is reommended to get a mesh prefilter, Summit sells them, 60-90 microns
I have gone though 4-5 carters in 50k.
If you lose your LP, your VP will likely fail within a year. It will run without the LP, but it will almost certaily doom your $1k+ VP44
I care a spare LP, just in case.
Good luck with your truck!

ProPerDoper

I installed a 1/2" high flow fuel line kit as recommended, from the filter to the IP. I did notice a change as it seems to spool a bit quicker, pulls a bit harder especially after dropping into 4th gear, and even the exhaust note sounds a bit different.

Tonight I installed a low fuel pressure warning light. Igottaflicker.... In fact, at sustained WOT I've got momentary solid warning light, so I suspect it's time for a new lift pump.

I've towed my 8k lb. 5th wheel about 2000 miles recently, including some pretty steep grades. Never noticed any sense of fuel starvation, but I'm told that's not surprising.

Hope my VP44 isn't damaged.....

I'm still leaning toward the Alliant replacement pump.

Lary Ellis (Top)

Those lights don't come on until you get as low as 5psi so you are likely even below that....Have you looked at the Fass DDRP? http://www.dodge-diesel.org/newdorepu19d.html

ProPerDoper

I have....and the AirDog as well. I purchased the low fuel pressure warning light from Pensacola Diesel, and phoned them this morning. After a long discussion, according to their tech it's not only normal for the light to come on during acceleration, but I shouldn't be concerned about needing to replace the lift pump until the light is constant at idle! It seems that although pressure is reduced as demand increases (load or acceleration) flow is still present to supply the VP44.

This is the exact reason I've been asking so many questions and researching as long as I have prior to buying a new lift pump. I'm doing my best to get passed the internet "mod everything" hype and make a smart decision about when to replace the lift pump, and with what.

I like the idea of a 100 GPH lift pump on there for peace of mind, and to insure supply given the minor mods that I have. I'd just like to choose when and what to buy based on sound advice so that I can make an educated decision.

Now....after all that rational thinking, I'll probably be in the market for a new lift pump soon.

Lary Ellis (Top)

I absolutely disagree with the tech that told you not to worry about it unless the light stays on at idle.....for 2 reasons that I have observed first hand over the 14 years I have been dealing with this stuff.....

1st... I NEVER want to see anything below 7 psi at WOT, anything less and you are adding stress on a fuel system we already know has serious flaws to it. We need lots of flowing cool fuel to help keep the IP from cooking the electronics or galling up the internals from heat damage.

Secondly..they call those little lights (idiot lights) for a reason...they are not as accurate as a real pressure gauge and it may in fact not be lighting up until it hits a much lower pressure than 5 psi. Even when using a real pressure gauge I like to test with a second gauge under the hood to be sure the one in the truck is reading the same.

I do agree with your wanting to stay out of the modding just to mod race that many people do, but on the other hand there are some areas that it doesn't pay to go "Cheap" On a 2nd gen 24 valve we KNOW the IP is prone to early failure caused by both heat and fuel starvation due to a lacking lift pump system.

With your mods I think (since I am not sure which Edge box you are using) you probably don't need a huge increase in fuel...but if you are running the Edge Attitude on a high HP setting then that changes your needs considerably.

The thing I try to point out to people is the money you spend on making sure the IP is fed with all the fuel it needs is money well spent. Sure your IP can still go bad as there are lots of variables involved here but anytime you take some of them out of the equation, you are money ahead

If it were my truck, I would not trust a $2000 dollar injection pump to a weak lift pump and a iffy at best idiot light....often guys have told me their little light didn't come on until AFTER the IP started acting up.

ProPerDoper

Good perspective sir...greatly appreciated.

I'm running the Edge handheld tuner Model EvoHT # 36000, set for Heavy Trailer, which I believe is 4 of 5 selections, or 2nd from the top being the "Performance" selection. If I recall correctly it seems the tuner was supposed to add about 160 ft. lbs. of torque. That combined with the CAI & Magnaflow exhaust are the extend of mods in terms of performance.

$250 - $300 for a lift pump is cheap insurance...I have to agree, despite the advice I've been given to stick it out until mine fails, so....

Assuming the Alliant won't do much more than the stock pump, I'm still looking into it a bit more. I like the Fass DDRP and the AirDog FRRP. Do you have a preference between the two?

Lary Ellis (Top)

I no longer sell the Airdog products because of premature failure...they were a good product until they sold out to another company and the quality went downhill.

I got tired of dealing with the poor guys who kept having to get pump after pump to try and keep running. It is good they were honoring the warranty on those folks that did what they had to do to get the long warranty but still they were without a truck for a week or more waiting on replacement....this isn't good for me or them...everybody loses.

I have not had any issues of this kind with the FASS products.

ProPerDoper

Man am I glad to be able to tap into your experience!

Dr.Dizzle

"If it were my truck, I would not trust a $2000 dollar injection pump to a weak lift pump and a iffy at best idiot light....often guys have told me their little light didn't come on until AFTER the IP started acting up". I agree with the comments that Lary made regarding the fuel system, especially the comment noted above. I opted to go with the FASS setup on my truck as well as our 01.5 CTD company trucks including mechanical fuel pressure gauges. I did this due to other owners informing me of the ineffectiveness of the idiot light. I lost one vp-44 and that was all it took.

The truck in my signature has been equipped with a FASS since 2006 and it has been trouble free. The same cannot be said about the AirDog product as the complaints of product failures and poor customer service are building up on this site as well as the other diesel related fora. Therefore, I recommend the FASS.

ProPerDoper

Very helpful....thanks!