Lack of upper RPM power

[4BTA4ME]

I've chasing a problem with my LDA equiped VE pump on my 4BTA Cummins engine. People at the 4BTA site don't have much experience with the internal workings of the VE so I thought I'd try the VW groups.
  I've lost a lot of boost (dropped from 27 psi down to 8 psi) somwhere during my last trip towing the boat and it just does not seem like the timing is advancing in upper RPM range. Checked my intercooler system for leaks. Checked my lift pump pressure (7-8psi =good). The engine starts very easily and it drives fine as long as I don't need more than 8 psi of boost. This translates to not being able to tow my boat up any mild hills because I usually run at 12 to 16 psi of boost when towing the boat on a hill.   I have my full load turned up slightly; sliding pin (cone) rotated to 3/4 of maximum fueling point; the  LDA top screw out for mild take offs; Timing advanced slightly. I also have what we call a 3200rpm governor spring used by 4BT type VE pumps to increase from 2800 rpm to 3200 governor control point.
  I'm wondering if I could have gotten some debree inside the pump somehow like a slight blockage in either the timing advance system like the pressure control valve or the overflow restrictor orifice. Or could my vane type fuel supply pump be hung up with dirt and operting at a lower pressure. Any ideas would be greatly appreciated.

[zukgod1]

I've chasing a problem with my LDA equiped VE pump on my 4BTA Cummins engine. People at the 4BTA site don't have much experience with the internal workings of the VE so I thought I'd try the VW groups.
  I've lost a lot of boost (dropped from 27 psi down to 8 psi) somwhere during my last trip towing the boat and it just does not seem like the timing is advancing in upper RPM range. Checked my intercooler system for leaks. Checked my lift pump pressure (7-8psi =good). The engine starts very easily and it drives fine as long as I don't need more than 8 psi of boost. This translates to not being able to tow my boat up any mild hills because I usually run at 12 to 16 psi of boost when towing the boat on a hill.   I have my full load turned up slightly; sliding pin (cone) rotated to 3/4 of maximum fueling point; the  LDA top screw out for mild take offs; Timing advanced slightly. I also have what we call a 3200rpm governor spring used by 4BT type VE pumps to increase from 2800 rpm to 3200 governor control point.
  I'm wondering if I could have gotten some debree inside the pump somehow like a slight blockage in either the timing advance system like the pressure control valve or the overflow restrictor orifice. Or could my vane type fuel supply pump be hung up with dirt and operting at a lower pressure. Any ideas would be greatly appreciated.

Well is sounds like a fuel delivery problem for sure.

Are you sure your LDA is functioning? Sounds like it's not receiving pressure from the intake to react properly. Check the hose going to the LDA.
Maybe back the star wheel way down so it will boost sooner and see what happens.
That little pin that rides on the cone can get stuck as well.
The timing will affect boost but not to the extent you are experiencing. It will still boost like it used to but your EGT's will be high due to the retarded timing.

I'm leaning towards the LDA at the moment. Go pull the hose off and go for a drive, if it is no different your LDA isn't working.

[jtanguay]

well something happened to go from 27 psi to 8 psi... it's either the turbo, the lines to the turbo or a fuel delivery issue which is impeding the extra fuel from spooling up the turbo further.

or it could be your lucky day and you just have a boost leak from the line going from the LDA to your intake.  mine came off one day and there was no guts up top whatsoever, and the boost gauge was reading 0 and would move a little bit if i stomped on it, whereas before it would go all the way to 20 psi if i stomped on it.  the reason my gauge didn't move is because it received its signal from the line that was disconnected  :lol: hopefully thats what your problem is, otherwise it will most likely be something more serious.

[4BTA4ME]

I am rebuilding the turbo (Holset HY35W) because it is starting to howl. I have to replace the turbine wheel shaft due to excesive wear on the shaft.
It is not crashing into the housing yet and is only a very quite howl when the oil is cold. I don't hear it making any strange noises after warmup. I even hear it wind down when I shut down the engine.
  The turbo boost on a Cummins is taken right from the intake plenum and is a 2 1/2" long hard line with compression fittings on both ends. Unless there is some sort of blockage on the inside of the plenum port for this it should be providing boost.
   I took the LDA off the pump and see good lubrication on the small pin and good movement of the pin when the tapered cone is out and moving  the lever down below. I had started to turn the starwheel up some when the diesel prices soared. I will turn that back down some more. I also have a shaved down spacer in my LDA for improved range on boost induced fueling; not that it can cause my problem.
   I can turn up the full-load screw. Just looking down into the pump it certainly has a huge effect on the fueling collar spill out point. Maybe it's just dumping out the fuel in the upper throttle arm region. Although I don't know how that could have changed.
   Question: What would happen if the "overflow restriction" port were blocked or restricted more than the orifice opening size or the pressure regulator were not working properly? Would that affect the timing?
   I plan on measuring the transfer (vane) pump pressure to see if the pump has a reduced output pressure.

[zukgod1]

It would affect timing, it would advance fully if the return was blocked. More pressure in the IP increases Timing.

[burn_your_money]

Do you have any air being drawn into the pump? Espeically at high RPM and under load.

[jimfoo]

Also, could your waste gate be stuck open?

[zukgod1]

Also, could your waste gate be stuck open?

Hmmmm..that's a thought.

I blocked mine off on my HY, took that little tube off and stuck a 22 shell in there. No more waste gate problems.

[VW_Commuter]

Also, could your waste gate be stuck open?

Hmmmm..that's a thought.

I blocked mine off on my HY, took that little tube off and stuck a 22 shell in there. No more waste gate problems.

I hope it was a USED shell   :shock:

[4BTA4ME]

It ( blocked overflow orifice) would affect timing, it would advance fully if the return was blocked. More pressure in the IP increases Timing.

Well I took off the overflow orifice and did notice that I was not able to blow brake cleaner into the small hole and out the larger screened inlet at first. I'm not sure what the engine response should feel like if it were overly advanced.
   My turbo is off right now for a new turbine wheel and shaft. I tack welded my wastegate closed at the control lever. I wondered if the tack welds broke loose but they are still holding.

Do you have any air being drawn into the pump? Espeically at high RPM and under load.

    I'm not sure how to determine this. The engine starts up immediately without any cranking. The mechanical lift pump is putting out 7-8 psi of fuel pressure and is right where it's supposed to be and the fuel filter has been recently changed out.

[zukgod1]

Well what it comes down to is a simple saying.

"It takes fuel to spool"

If your not getting the boost pressure you once had you either have a fuel deilvery problem or a air problem.

[burn_your_money]

How is the truck off boost and at idle? Smooth, normal power?

[4BTA4ME]

It's very driveable under mild acceleration until I get up to 70 mph. Pedal input provide very little acceleration after that. But, I guess I've always been in the >8 psi boost range when up in that speed range.
  Maybe it does just need some more fuel with the max torque adjustment.