Engine/Transmission (1998.5 - 2002) Difference in Lift Pump & VP44 Injector Pump

[HeavyHauler]

I've got the 2001 truck with the apparent "lift pump" problems. All I read about on here is the lift pump and the VP44.



Could someone give me a definition on the two and what it is they acutally do? I couldn't find a thread that compared the two. (I don't even know if they're related)



Just need a basic run down on these two components.

 

[csutton7]

they're related--the lift pump sucks fuel from the tank and then pushes it thru the filter to the VP44 and then the VP 44 pressuerizes it and pushes it to the injectors---lift pumps usually go first--that's why most if not all get a fuel pressure guage installed ASAP to monitor the dang thing--there's a ton of info and reading on these two--hope this helps---chris

 

[jwinnie]

Ok, here is a VERY basic (as I'm no expert) run down:

The lift pump or "transfer" pump is a small, low pressure electric pump mounted on the engine block below and aft of the injection pump (VP44) on the drivers side of the engine. It lifts/transfers fuel from the tank to the main injection pump (VP44). The VP44 is the heart of your engine. It sends fuel to the injectors at a precise time and VERY high pressure (14,000+ psi). It is also cooled and lubricated by fuel. When the lift pump fails, not if but when, the small internal lift pump on the VP44 has to work double duty to supply fuel to the high pressure pump. Under high engine loads alot of the fuel that should be cooling and lubricating the VP44 is not there. This shortens the life of the VP44. A fuel pressue guage should be the #1 mod for any 24V owner (IMO).

Hope this helps and someone chimes in if I got any facts wrong.



John



Edit: Chris, I type too slow, you beat me to it.

 

[HeavyHauler]

Thanks for the info!

That's just what I needed to know, couldn't have been said any better.



Thanks guys.

 

[isb360]

Has anyone looked at VP44 failures caused by lift pump failure vs. straight out failure of VP44?



In other words, are most VP44 failures caused by failed lift pump or are there a significant number of "bad" VP44's out there.



I'm at 102k, bone stock, with no problems. I have an Autometer Fuel pressure on order with Geno's Garage and am getting itchy about checking post-filter pressures, especially since I am on the brink of bombing. I have been tempted to replace the lift pump just as a PM item, but want to monitor pressures first.



Thoughts?

Tim

 

[SEmerson]

A lp my last along time or could be bad oout of the box. You need to monitor it instead of just changing it.

 

[csutton7]

I'd say a lot more vp's fail due to the lift pump failing first vs the vp's just failing by themselves... . chris

 

[Oil Burner]

I think that most commonly on a STOCK truck you will find that the injection pump fails relative to a bad lift pump. Bombed trucks are a different story, especially when a box is added. Some have had no trouble with boxes, others have lost VP44's after adding them.

 

[isb360]

Yes, before bombing, I am going to monitor LP -- not just replace it. I've seen a VP health monitoring device (I think from Blue Chip) and am wondering if that can be used as an indicator of impending failure with or without a box.



Tim