sparky3008

Ok, I am a Computer "engineer" and for all you real engineer I use that term loosely. Anyway most of the time we are not real proactive, we wait for a problem and then fix it. With my truck I want to be truely proactive, hence my questions.

I see many putting in Lift pumps for high pressure when increasing HP. Much talk about injector pumps and so on.

I have just recently added a Bully Dog downloader which of course will call for more fuel.

My first question is: Are the Lift pumps that most are adding in addition to the original lift pump so now you have 2 or do you replace the original with the bigger?
Second question: I understand that diesels are direct injected, meaning that air is compressed first then fuel is "injected" and the compressed hot air causes the fuel to ignite. What I don't understand is the difference between a lift pump and an injector pump???
Third question: Do we replace the injector pump with a better high performance one like the lift pump or do we just do that if it goes bad aka have a spare around?

sparky3008

Ok, I found this.
The VP44 injection pump was introduced on the Cummins ISB as a stop gap measure to meet 1998 emissions standards before a common rail fuel system was ready for production. For Dodge Ram pickups, the ISB engine was used in all trucks built after January 1, 1998. A common rail system is being road tested now, and reliable rumors say the the VP44 will be replaced by a common rail in 2003 models. For those with 1998-2002 Rams, here are some details about the VP44 pump.

Does this mean that since I have an 03 common rail that I do not have an injection pump?

If I understand this any at all the lift pump pumps fuel from the fuel tank. The fuel gets to the common rail on mine or on older models the injection pump. Then from there the common rail or injection pump distributes the fuel to the injectors??

Shovelhead

The lift pump's job is to move the fuel from the fuel tank to the Injector Pump.
It supplies more fuel than to the IP than is needed to run the engine and uses the excess to cool the IP and then returns hat fuel to the fuel tank.
The fuel pressure provided by the Lift Pump is in the 15 psi range, whereas the Injection Pump provides pressures in the thousands of PSI range.

sparky3008

Ok I am still confused because now I see mention of the CP3 on the 03's. Some seem to indicate them leaking because of addition of high pressure lift pumps such as the BD Diesel Performance pump I was thinking about adding.

I know someone knows this stuff...
Thanks

sparky3008

I found an existing post that described this fairly well so since no one seems to be answering anyway I will consider this closed.
Thanks

MCummings

sparky,

You have a great idea of how things are really working.

On the older trucks, '89 - '02 there was a fuel tank, or transfer pump, and an injection pump..

#####--------*---------&-------^^^^^^
Fuel Tank, Trans Pump, Inj. Pump, Injectors

Common rail motors like yours, have a similar setup,

#####--------*-------(*)-------------@@----^^^^^^
Fuel Tank, Trans Pump, High press pump, Rail, Injectors


The "High Pressure Pump" replaced the injection pump of days past. Not the injectors have a steady supply of high pressure fuel available to them, even at idle, and are opened and closed electronicly.

In days past, injection pressure was highly dependant on engine RPM. At idle, injection pressures were very low, and as RPM increased, injection pressure also increased.

This was very bad for emissions.

Now we can have extremely high injection pressure at idle. Not only does this give us great emissions, it's great for aftermarket too, becuase alot of fuel is available right off idle, and we can control when, and how long the injectors stay open.

With your bully dog programmer, you should look into replacing your factory transfer pump (often called a "Lift Pump) with a FASS pump. You don't need all the fancy filters,,, just the pump itself, which if I recall correctly is under $200.

That FASS pump will push enough fuel to your high pressure pump for any HP number that even a seasoned HP junkie would want

Besides running additive, thats about all you can do. The rest of the story is in the hands of daimlerchrysler.

HTH,
Merrick

sparky3008

Thanks,
Yea in my reading it looked like the cp3 can pull fuel on its on but if the lift pump went that is futile as it wouldn't get anything past the dead lift pump anyway.
Question: Does the FASS replace my existing lift pump?

MCummings

Yes.

The CP3 can suck through a dead lift pump, but the truck will be really low on power.

If you want to do a little more research, check into the "RASP". It does not replace your Lift Pump, it wil actually run in tandem.

The RASP is a full mechanical, belt driven pump. Look into it, it is a great investment, but over $600.

Merrick