montemorris

Sorry, I just posted this in the first generation by mistake.

I just had my 01 2500 in for an oil change and general check up today. The mechanic questioned my fuel pressure (I have an isopro gauge) which is at 7-8 psi at idle. No one in the shop thought that the psi should be that low.

I'm on my 3rd lift pump; the last one has lasted 70,000 miles since they put it in the fuel tank instead of under the hood. This was maybe 5-6 years ago. It was installed by a Dodge dealership and they told me that I would notice that my pressure would be only about half what it was before when the lift pump was under the hood. They were correct as I immediately saw 7-8 psi at idle and sometimes down to 4 psi when towing a fifth wheel.

It seems that the Dodge dealership that installed this last lift pump said that there had been a technical service bulletin about the old lift pumps and that they should now be installed in the fuel tank.

Question. Was the dealership that installed the pump correct that the pressure SHOULD be that low, or are the current mechanics correct that it should NOT be that low? The truck runs fine since the installation, but should I be worried that the injection pump is not getting lubbed? I'm NOT very mechanically inclined, therefore in the dark about this. Thanks.

cougar

If you do a search, this subject is a never ending argument. My personal opinion? 7psi is rock bottom and still not good enough for the health of the injection pump. Over 20psi can damage the diaphragm. Keeping fuel pressure between 12-16 is pretty good all around. Moparman73 has some good info on the subject.

oliver foster

I answered this question in the 1st gen section, as I also have a I have an '01 as well.

SIXSLUG

The fuel is the lube, the pressure pushes sufficient fuel volume through the pump to cool it, that is also why we try not to run below a 1/4 tank of fuel...

5 psi is the dealers minimum so they say, but the rebuilders feel this isn't enough to elongate the lifespan of the vp.

I would visit bluechipdiesel.com for some informative reading...

KATOOM

The ONLY component lubricating and cooling the VP is fuel and excess fuel. Running the fuel pressure too low causes the VP temp and fuel temp to increase which is bad for the timing piston and computer. And also pressure that low allows for the hydrodynamic fluid pulses coming from the rotor to pass through the low pressure side of the VP. The only thing stopping those pressure pulses from cracking the diaphragm in the VP is the pressure from the fuel pump, which is at least or higher than the low pressure side of the VP. That minimum psi is around 10. Note that the OEM lift pumps were regulated at 15-16 psi but unfortunately had a very high failure rate and its not uncommon to see one barely able to maintain what you're experiencing. So much so that Dodge thought the fix was to install a higher volume / lower pressure fuel pump in the tank. Needless to say, that wasnt the answer and those fuel pumps were equally bad. Do NOT let a dealer install the intank pump. You can keep installing Carter lift pumps on the engine or find another aftermarket fuel pump which is capable of sustaining the needed fuel pressure to keep that VP happy. That said, the general consensus from many years of collected trial and error testing and experimenting by consumers and aftermarket companies, running fuel pressures no less than 14-15 psi at any time is best. Most aftermarket fuel pumps will be able to run at around 18-20 psi to achieve a WOT psi of around 14-16 psi.

Its a good thing you have a fuel pressure gauge.

montemorris

Thanks for all the advice. I'll install an aftermarket lift pump. I'm leaning towards the Raptor since it is mounted under the hood, has a 4 year warranty, and doesn't have a filter to screw with. Comments?

KATOOM

I'm not sure what pump to suggest anymore since there's differences between all of them. FASS was one of the first to introduce the frame mounted pump and filter kit. Pureflow was a relative of the FASS company who spun off the company and created the Airdog and Raptor. For awhile they competed with almost identical products but I understand Pureflow sold out and whomever took them over wasnt as interested in quality as they were income. Needless to say there was a few years where PF pumps and their customer service had many issues. I hear they're much better now but I cant say one way or the other.

I have one of the older (pre-sell out) Raptors mounted on the frame. Seems like a quality unit and mounting on the frame is always better than on the engine. Plus increasing the fuel line size and changing all the supply line fittings from banjo to JIC helps tremendously.

In saying all that, personally, if my Raptor ever fails and fixing it becomes an issue then I'm switching over to the Fuel Boss mechanical system. I hear great things about those kits.

hallio217

I would recommend the Factory Replacement Raptor Pump (FRRP). Its rated at 100 GPH and the pressure is adjustable. Ive had it for about 5,000 miles and have been very pleased. Pressure is at 15psi idle, but I could turn it up as high as 22psi. 4 yr warranty, easy installation (although youll have to remove your old lift pump from the tank, I had to do the same thing), and the purchase includes 1/2" lines.

http://www.xtremediesel.com/pureflow...rpumpfrrp.aspx

jrs_dodge_diesel

Moved to 24 Valve Engine and Drivetrain forum

I had two OEM lift pumps go out before I replaced mine with a FASS DDRP. Works good for me.

george7941

I have been running a Walbro pump, bought for $115, for the last six years. My pressure regulator is set to 11psi and it seems to suit the VP44 just fine. My Freightliner truck has 210k miles on it but more importantly, the ECM shows the engine run time to be about 14000 hours, which is a pickup truck would translate to around 500k miles. I still have the original injectors.

bradshaw106

I have a fass and it runs @25 psi. Been like that for a long time.

dkenny

do some searching on the 'diaphram' in the VP44...
there isn't one..or i'm not understanding what's ment by diaphram..
eitherway..do some digging..

for me I've not found anything difinative about low pressure killing the pumps.
now it might be a secondary cause..as in not enough fuel cause the electronics to overheat..over time..ok..that I get..but the paranoid over
fuel pressure under 5psi the VP is dead..as in if it goes under 5psi just once..
the VP is dead..garage..if under 5psi kills the VP why is mine still running?
think 10 in vacuum..several times..has yours..do you have a vacuum/pressure gauge or just a pressure guage? so you might not know yours has seen a vacuum....

-dkenny