Engine/Transmission (1998.5 - 2002) Lift pump replacement

[Tractorat]

My regular mechanic tested my lift pump and said that, under just a light load, it drops down to less than 2psi (15psi at idle). So, I took it to a dealer to test and for a warranty replacement. Dealer says it only goes down to about 5psi at WOT. My mechanic says the dealer doesnt know what he is talking about. He asked me if the dealer actually road tested the truck. He says this is the only way to check it.



Should I believe my regular mechanic and not the dealer ? (thats my inclanation)



Thanks in advance,

tractorat

 

[nps]

Hard question. One wants to do the work for you and says it's bad, while the other one wants to avoid the work and says it's good.



YES - you must road test the truck to monitor. You can't do it sitting still because the motor isn't generating much HP without a load, thus is not demanding the VP to use much fuel.



The dealer is also supposed to test the pump with volume, not pressure. Your volume test may not fail. So the dealer may just trump you on the pressure test, check the volume (44 oz minimum during the 25 sec LP run cycle after bumping the starter), and call it good.



My LP sounded like yours (actually mine was a little weaker). I DID NOT change it. Rather I put on a frame mounted Carter 4600 pusher that puts out 8psi, and I now enjoy 14 idle and 9 WOT. Has been good and steady for over 6 months now. Cost about $100 from Summit. Another option your mech can do for you.

 

[BK]

Based on those readings, and from experience with my LP, I would replace it.

The dealer is going to be a tough fight, took me a 3 hour fight, well under warranty.

This was before the volume ruling that they now use.

Back then it was 10psi or great at WOT while driving.

My 5 start DC dealer didn't believe me and didn't know any better.

I got them to call Cummins on their Cummins hot line , Cummins told them every thing I did. So they hooked up a gauge , took it for a road test, and it failed.

I measure zero when I did it, they measured 3.



I went about 25K on that replacement pump, 13 idle 10 wot. It's now acting funny.

Some times down to 6 after the engine first starts. 8 for a while , up to 10 during the rest of the day... all at idle. Then at times 6-8 with a heavy foot.



the vp44 needs volume of fluid to 1) use for the engine, 2) to send back to the tank as cooling. . heat gets carried away. So if the volume is too low, not enough to run well and not enough cooling.



To me , all things normalized, like filters , fittings, hose sizes... that pressure is relative to the volume based on fuel system restrictions. . which is important to the pump being able to deal with "head pressures" and pump into the vp44 and filter, as well as draw from the tank. So under real world work, to me the pressure is a more valid test than filling a freekn bucket.





Go to the 70 lp thread, get numbers and buy 2 new pumps.

https://www.turbodieselregister.com/forums/showthread.php?t=151407

Get either the vulcan big line relocation kit, or the Geno's version of the Vulcan 3/8 line kit.