I found this VERY interesting post on another forum. Seems this guy knows his stuff.
http://www.cattletoday.com/forum/post-406859.html
I wrote this up for another list, but thought some may find some use for it here:
It seems like this topic comes up once in awhile on here, so I'll rattle
this off to clear up misconceptions and hopefully prevent guys from spending
big dollars on what amounts to a bunch of un-needed junk.
First, to clear up a fallacy I see repeated over and over again:
Dodge lift pumps, in their stock location do NOT suck fuel. Or at least,
not enough to remotely hurt an electric pump. If you don't believe me, fill
up your fuel tank and pull the inlet line off your lift pump. Leave it in
the air at about the level of the lift pump inlet and let the fuel run out
of the tank. You'll drain the 30 gal tank in about 15 minutes. Thats 120
GPH flow. The stock lift pump is only a 90 GPH pump. You do the math.
1998 - 2002 VP44 equipped trucks.
As has been mentioned, these trucks are prone to lift pump failure, even at
stock power. These pumps are a pretty basic design pump. About the only
thing fancy on them is an internal bypass valve (check ball) to prevent over
pressure.
I sat down with my local Dodge tech and pulled down a whack of lift pumps.
Well, a dozen. But it felt like a whack. On 10 of these pumps, the check
ball bypass valve was not functioning. One even had the checkball driven
through its spring and was on the wrong side of the spring. Of the other 2
failures, we had 1 failed electric motor and 1 broken teflon bushing that
holds the pump vein to the motor. In other words, only 1 failure in 12 that
could remotely be blamed on long fuel draws (the burnt motor). Since that
little episode, I've pulled down a few more pumps and seen bypass valve
failures in EVERY single one of them.
In other words, these guys yapping about the lift pump failures being due to
the long _pull_ from the fuel tank are full of crap. And that includes
Dodge with their goofball in-tank solution.
So why the checkball failures? As the VP44 is using fuel, the line pressure
between the lift pump and the VP44 drops. The VP44 and subsequent injection
system has a max flow rate of around 75 GPH in stock trim. So that means
that the lift pump is able to pump more fuel than the VP44 can consume, even
at WOT. The design of the VP44 compounds the issue, in that it doesn't just
smoothly flow fuel but rather takes little gulps of fuel at a time via its
own little sliding vein pump. Which means that the lift pump check valve is
continuously working.
However, this wouldn't normally be a problem, except for one thing: At each
joint in the fuel system (2 at the lift, 2 at the fuel filter, 1 on the VP44
pump inlet) there are banjo bolts with crossdrilled holes. These banjo
bolts, with their small holes, are not even remotely capable of flowing 90
GPH. So this means that the lift pump is trying to pound 90 GPH against a
fitting only capable of flowing _maybe_ 65 GPH. In other words, the flow of
fuel through the system is disjointed and erratic as it passes through each
joint. Which means that the pump bypass valve is flicking on and off like
mad, well past the design limits of the checkball/spring combination causing
early failure.
So how do you fix it? At stock and near stock horsepower levels, its easy.
Make the banjo bolts flow more by opening up the cross drilled holes from
the stock size of .135" to .187". I found this was plenty large enough to
allow fuel to flow smoothly in the system and reduce the stress on the lift
pump. The larger banjo bolts would reliably support 300 to 320 HP. The
only proof I can give you is that trucks putting the banjos on went from
failures every 30,000K to still running strong at 100K or more.
Past the 300 HP level or for guys who spent alot of time at WOT, we found
the banjos still didn't quite flow enough. The answer was to replace the
banjo fittings all together with custom built -8AN fittings and -8 hose. I
did this between the lift pump and fuel filter housing, and between the fuel
filter housing and injector pump. This worked very well up to around 375HP.
Past that point however, I found the stocker lift pump couldn't handle the
bursts of fuel required at WOT and eventually the internal bypasses would
fail again. The answer was simple. Find a higher flow pump, around 150
GPH. We didn't need the additional fuel flow, but these higher flowing
pumps had heavier built check valves that could handle the abuse that the
VP44 exacted on them. I preferred the Holley series and the Product
Engineering pumps, however others had great luck with Carters too. There
were alot of issues with Holley pump quality for awhile, however we found it
was simply a matter of pulling them apart and cleaning up some of the
castings.
I looked at mounting the pumps back by the fuel tank, but realized that in
the snowbelt those pumps were fully exposed to the elements, and we knew
from competitor experience and the RV market that pusher pumps often rot
away back there. Not to mention that pushing that distance was asking alot
from a small pump, and often times the teflon bushings that mate the veins
to the electric motor would disintegrate back there. It is pure fallacy
that small electric pumps can push diesel fuel long distances without
wearing on the pump drive components, but rather the pump has to be
specifically designed to do that. None of the cheap $100 pumps are designed
for this style of application. As a final killer to the idea of mounting
pumps back on the frame rail, I noticed that many pumps sat level with the
bottom of the frame, or even slightly below. For anyone driving in deeper
snow, mud, or off-roading, that pump was just ASKING to get torn off and
leave them stranded.
So I chose to mount under the hood area, up on the frame rail where it
starts to curve upwards for the front suspension. I noticed this area was
well protected from salt and water spray by the front axle, and was high
enough up that it couldn't be tore off when off-road. Also remembering how
much fuel transfer there was from the tank, and I thought I'd found the
perfect mounting spot. I called both Holley and PE, spoke to the actual
engineers in charge of designing the pumps, and verified that a distance
draw wouldn't hurt either of these pumps. Indeed, I got the same response
from both companies: Horizontal distance draws do not hurt their pumps, but
rather its the vertical draw you need to worry about. Both companies
recommended that I not draw more than 2 feet in the vertical (distance from
bottom of pickup tube to pump inlet), and I was well within that tolerance.
I built a custom bracket that used existing holes in the frame to mount the
pump, but there was no issue with drilling for a different bracket either.
Mounted in this location, I found that there was ZERO pull down on fuel
pressure, no matter what pump I used, no matter what horsepower level I was
at. I've got customers sitting at 600 - 650 HP on straight diesel, and have
been running strong for three or four years with the SAME pump in place.
As a side note, this lift pump failure syndrome is not limited to ISB
Dodges, but rather all VP44 ISB equipment. And the one thing they all have
in common are those small banjo bolts. Lift pump location varies, and they
all experience pre-mature failure.
2003 and up CP3 equipped trucks.
The little pump that comes stock with CP3 equipped trucks is a pretty weak
kneed little critter, but it is well suited to stock horsepower levels with
only a little draw down on pressure at WOT throttle loads. I never did much
experimentation at stock power levels, however I did install higher flow
banjo bolts. As I expected, they didn't do much to affect flow, as the CP3
equipped trucks are already sitting at what I considered the upper limits
powerwise for high flow banjos. I do however believe that the higher
flowing banjo would help with early failures on stock powered pickup trucks.
As soon as I started modifying the truck, I immediately replaced the lines
with -8AN lines, but left the stock lift pump in place. I found that any
kind of power increase over stock would immediately show a pressure
decrease, even with the large lines installed. So I built an adapter, and
stuffed a 14PSI 140 GPH Carter pump in the same location as we did with the
VP44 equipped trucks. End result was ZERO draw down on pressure, even at
the 500 HP level. I ran like this for a couple years, and never once had a
burp out of the cheap Carter lift.
So what can you do to your truck?
If you plan on buying an aftermarket fuel system for your truck, skip by ALL
the goofy pusher pumps. Complete waste of money, and you ruin the utility
of your truck. The FASS system and AirDog mount back on the frame rail by
the tank, and their additional filters hang BELOW the frame rails. To my
way of thinking, this is extremely bad design.
If you plan on modifying your truck past 300 HP, find yourself a system that
replaces all the lines and banjos forward of the lift pump. If these lines
are not replaced, you're wasting your money on everything else. Depending
on your horsepower level, you may or may not have to replace the pump. If
you want to build your own system (the cheapest route), contact Earls and
get a set of their aluminum -6 adapters. They're available off the shelf.
Then go to NAPA and buy some pushlock fittings and -6 diesel safe pushlock
hose. Then buy a 140+ GPH pump from favorite manufacturer and mount it
under the hood where its protected. I know I used -8 lines, but -6 would be
lots right up to 500 HP.
I hope this helps, and I hope that it saves some of you some money.
Rod
http://www.cattletoday.com/forum/post-406859.html
