Time For Lift Pump???

[SmokeSmacked02]

I have been tuning on an 2005 LLY truck. Modifications are AFE Intercooler tubes and boots, fuel rail pressure relief valve shim, transmission kit put together by a local builder with transgo shift kit, AFE intake, 5'' exhaust, LBZ mouthpiece, EGR delete plate, EFI Live DSP5, 6'' lift turned down a little to get CV angles right, 305/55/20 tires. Now my question is how to tell if a lift pump is needed? I have only been tuning for two years locally and have not had many trucks come up to me with many modifications. A lift pump is always a good thing in my eyes but when dealing with other people money I like to prove that the truck needs a certain modification with real numbers or performance issues. Is there any way to detect this with data logging? I can notice the engine starting to pull back at a little higher rpm's but the boy is not satified with that judgement alone. If there is any ruel of thumb for this it would be well appretiated.

Thanks to all,
Daniel

[THEFERMANATOR]

Log rail pressure and see if it is holding up top. Low rail pressure is normally indicitave of needing a lift pump.

[LB72004]

Log rail pressure and see if it is holding up top. Low rail pressure is normally indicitave of needing a lift pump.

2x.

[Wheelz]

Install a fuel pressure gauge and see if it starts losing pressure under high load too.

[aubleak]

Install a fuel pressure gauge and see if it starts losing pressure under high load too.

Wouldnt that be more difficult then just plugging in a scanner?

[Boost]

Beat it up until it sets a P0087.

[Wheelz]

Wouldnt that be more difficult then just plugging in a scanner?

You cannot monitor pressure before the cp3 with only a plug in scanner

If you starve the cp3 for fuel, just plan on buying a new cp3. It's the fastest way to tear it up. You can log rail pressure or watch it on a scanner all the time while your driving. But the fastest way to know if you need a lift pump is with a fuel pressure gauge after the fuel filter and before the cp3

[Boost]

Isn't there also a sort of a rule of thumb where after a certain HP you need one? For instance I would say that over 500 wheel hp a lift pump is pretty much mandatory. Maybe even below. And aren't there benefits of running one even before it is needed?

[THEFERMANATOR]

Isn't there also a sort of a rule of thumb where after a certain HP you need one? For instance I would say that over 500 wheel hp a lift pump is pretty much mandatory. Maybe even below. And aren't there benefits of running one even before it is needed?

I was always told once you go over 400RWHP, you should definately consider a lift pump just to keep the CP3 happy. I know many have went from 425-440 on the dyno to 450-460 by adding a lift pump and being able to hold rail pressure. Also I just rebuilt my filter head, and when I was doing it I checked the drainback valve to see just how much vacuum it takes to fully open. The new filter head and old one both took 20 inches of vacuum to fully pop the check valve off its seat. I dropped the spring tension back to about 3-4 inches of vacuum, and now my BURB is a friggin animal up top.

[Boost]

Cool, thanks for the info! I suspected it was much lower than 500 whp. I've had customers lose pressure on around 450 rwhp tunes.