I just bought this 99 3500 and was enjoying it very much,
until just the other day. It started with very sluggish take
off, and progressed into a very low power below 2200 at which
point the turbo would spool and i could move normally. It was
suggested that i replace the fuel filter, so I did that. However,
upon doing that i could not get any fuel back into the system.
So logic suggested the pump. Had a holley blue so I threw
that in and now I have plenty of fuel. Truck starts fine, idles
fine, just as it always did. Now I have a little power back
again, but it sounds like the turbo isnt spooling as it used to.
Power is still low below 2200, but now the turbo spool isnt
as loud as before and above 2200 i have low power as well.

Another interesting thing, the TC appears to be locking up
very early. All shifts feel like the TC never unlocks and even
tapping the brake pedal produces no rpm change as before.
It must be unlocking because it can idle in gear, but once
moving it locks up all the way. Can the two be related at all?

Im stumped and i hope someone here can help shed some
light on this situation before i go dump money at either dodge
or the cummins dealer.

 

From what you say, it sounds like you have a failed lift pump. The bypass section of that pump will restrict full fuel flow, so even with a booster pump your pressure will still be low to the injection pump.

The TC lockup problem may be caused by your booster pump installation, if you tapped into the existing lift pump power source. That will cause interference with the ECM and the controls for the automatic transmission.

 

I am fighting a very similar situation with my '99 3500. I can drive down the road and loose power but can regain power by putting in the clutch and letting the engine idle for a second. My truck will also idle perfectly. I first changed the IAT sensor and the MAP sensor with no change in performance. I then changed the lift pump and this helped considerably, but did not resolve the problem. I fear my problem is that the VP44 injection pump is going bad. I do not drive the truck very often and am away from home for a month, so I have not been working on my truck. My next step is to take it into the dealership to try and pull codes. If this does not work, I am going to drop the truck off at a Cummins dealer to figure it out. Good luck with your truck.

 

[quote author=RCW link=board=13;threadid=20845;start=0#msg195654 date=1065893821]
From what you say, it sounds like you have a failed lift pump. The bypass section of that pump will restrict full fuel flow, so even with a booster pump your pressure will still be low to the injection pump.

The TC lockup problem may be caused by your booster pump installation, if you tapped into the existing lift pump power source. That will cause interference with the ECM and the controls for the automatic transmission.
[/quote]

no booster involved. i completely removed the old LP and i used a relay to power the holley.

Could it be the injection pump?

 

Check your intercooler ductwork, make sure there are no leaks at the rubber elbows. Sometimes you can see a witness mark where the rubber will slide out from under the clamp under full boost.

 

I belive the injection pump is all or nothing.

 

[quote author=scooter link=board=13;threadid=20845;start=0#msg196051 date=1066009319]
I belive the injection pump is all or nothing.
[/quote]

That was my estimation as well.
Well, today since i had nothing better to do, i pulled the
batteries and recalibrated the APPS. Voila! The truck appears
to be normal again. The strange low power problem came
back twice today, but turbo is spooling again and everything
appears to be normal otherwise. Maybe my VP is going
and ive just bought myself some time. Or maybe im just
paranoid. Either way, I think I'll start saving my pennies
for a new pump.

Thanks to everyone for all the responses!

 

I don't doubt that the pump could be going, but possibly you have a bad APPS. Better check your codes, if the pump is going it should say that.

 

Ok, i finally went to the diesel repair shop.
No error codes, but map sensor was not seeing boost.
Got a replacement and everything is good again.
The one thing i didnt think it would be.