I have been thinking, I know that's the first mistake. The IP increases fuel pressure from approximatly 7psi to 3000psi. Thus the fuel lift pump (LP) is only needed to prime the system at start up and bring fuel closer to the IP. By increacing the capicity of the pre IP fuel system the IP will have to work a little less which should extend its life. But I can not see how the feed the beast mot or a larger LP will improve performance.

If you happen to think the stock system is undersized I suggest that you disconnect the fuelinlet to the IP and turn the truck to the on position. That activates the LP and you will see fuel shooting out of the hose.

 

More fuel = more power (if you can burn it all). All a larger lift pump will do is able you to get more fuel to the engine, on these engines, probably not worth the money. I can get black smoke with a stock setup and a cold air, so I don't need to get more fuel. Unless you're running more than stock boost (7 psi) you probably just be wasting money. I've only had mine for a year in a half, so I haven't had problems with the IP yet, so my opinion might change if I start having problems, but the IP should last a while as long as the PMD is remote. I see on some of the older Cummins, they put huge lift pumps on just to increase the fuel supply so they can run 600 hp, not really possible on a 6.5.

 

If I understand you: Because the IP controlls the quantity and frequency of fuel going in to the engine if the engine is left stock the stock LP would be adequate. But if the IP is reprogramed then it may need additional fuel quantity and pressure pre IP.

 

Stock LP is plenty adequate to provide for the engine's stock needs, unless you are running high boost levels it's probably not worth messing with. A good way to check is to and see if you can get it to smoke, the smoke indicates that there was fuel that wasn't burned completely. Don't punch it off the start, get the engine running at a good rpm like 1500+ so the turbo is already working and try this, if you don't get any smoke at all then it might be worth upgrading. But just a pure stock setup, the stock LP should be adequate, unless you like blowing lots of smoke, around a Prius perhaps. The IP usually isn't the thing that goes bad on these, the PMD on the IP is what goes bad from the heat changes it gets located on the IP. If you get a tune for it, still check to see if it will smoke, if it can't burn all the fuel already why increase the volume? More less, I think the "performance" LP are made for those who put the holset turbos on theirs and run 25+ psi, the stock system is set a 7 psi and this engine was designed to be relatively smokeless, they shouldn't really smoke at 10 psi, they just go for overkill and the whistle. If its stock, best bet would be to leave it alone, by the time your actual IP goes out, it be time for a new pickup anyways. But if you do want to make some real power out of these, then the bigger lift pump is worth it. Mine is basically stock (cold air) at 197k miles and gets all of its fuel needs still.

 

My truck stock programming saw 12PSI of boost. Before I did the FTB mod I could not get my fuel pressure to drop below 2-3PSI at WOT. So I decided to do the FTB and do a lift pump when mine went bad. After installing the FTB I could pull my fuel pressure down to a vacuum. That tells me that the stock lift pump only keeps up under the small 1/4" fuel line and once you supply more fuel to the IP(that the pump is obviously using or the pressure wouldn't have dropped to a vacuum) the truck just seems to run better when towing or when more power is needed. So then I did the Walbro FRC-10 for my lift pump.

 

The reason it is done is that even on a stock truck sustained high load can reduce pre-IP fuel pressure to 0 psi limiting power.
Some of us add a fuel pressure gauge pre-IP to monitor the LP and fuel filter condition-if you get a bad tank of fuel you know right away what the problem is.

Although if you run with an EGT gauge you would be limited on how long tou could sustain that full throttle.

So once an aftermarket tune is introduced the need for more LP capacity is increased.

 

not sure if its true but i read our ip is a staynadyne and it requires (from specs)9 psi fed to it.
none of the stock not even the 93 lp can produce that. this would explain a lot of ip failers i think and pmd getting hot.
what i cant get over is, if this is true gm knowingly set us up for our ip to work overtime right out of the gate.
i'm in the middle of upgrading my lp to a frc10. my current pressure at idle is 6psi at ffm i can only guess it drops at wot. 150$ to save a 1200$ ip in my eyes.