02 CCSB LB7 severe lack of power (like a 4cyl)

[Diesel Krazy]

I have a truck that I bought a while back with some preexisting problems. 02 2500HD LB7
The main problem is the thing can't get out of its own way. When stone cold, it barely responds to throttle input, barely comes off idle even when floored. As it warms up it gets better, but acts like it is limited to 1/4 throttle or less other than trans shifts late or kicks down on heavy throttle input.
It starts easily when cold and runs smooth with no unusual noises. No CEL ever.
No smoke and 11 psi is the most boost I have ever seen.
Almost tolerable it I load level 4 tune, but only with heavy input.
My bone stock LB7 3500 flatbed running on 7cyl has way more power. It has a valve train problem.. :-(
I have Torque Pro for logging, but it has its limits. Can't afford EFI Live yet.

New Fuel filter (Dealer tested for restriction in fuel system @ 2hg)
Tested Rail Pressure and it scales properly and Demand / Actual stay close.
Injector Balance is within spec. (Injector Age unknown) Not Making Oil!
PO did head studs 30k ago and Truck has 210k on it. (Said He couldn't afford to do the injectors then.
Checked engine harness connectors and 1 pin was pushed in a little, but no change.
Cleaned MAF and swapped with other truck, No change.
MAP Seems to scale fine ( Maybe I should swap with known good?) Cleaned, no help.
New Batteries and have tried another pair.
Currently set to stock and ECM was updated at dealer recently with no change in power.
The only think tech said was MAF not scaling to 450? I was able to get there but it took a while. Cleaned / Replaced made no difference.
Had an AFE intake on it, switched to stock and noticed a slight change, but not much.
Changed Trans Filter and topped off ATF as I heard that could affect it.
Exhaust is a 4" MBRP SS Catback system so no restriction there.
Not California model so no EGR.

I am at a loss why it refuses to give it fuel, like something is holding it back. Anyone nearby have EFI Live or a tech 2? I can only do basic checking and logging with Torque Pro and I can't afford to go back to the dealer or throw parts at it. I have spent many a night researching and testing only to come up empty handed so far. Maybe if I get a chance I will recheck or swap out MAP and even the AP? Sensor. I believe they both show the same with key on.

Any help solving this would be greatly appreciated...

[DmaxMaverick]

Brakes sticking? Check for free-turning wheels. The E-brake may be stuck. It's happened before.

Other than that, it sounds like you'll need some hands on. Other than checking for actual fuel flow (collapsed line, other restriction), looks like you covered the basics.

[Diesel Krazy]

No problems with the brakes. It is even sluggish to rev the engine with no load. I just did some more logging to look at fuel rate and it looks like the ECM is holding back on fueling. Swapped MAP with other truck and seemed to help ever so slightly and was able to get 15psi if I floored it long enough uphill. It is a fueling issue for sure, just can't figure out why. Seems like something is telling it to limit fuel??? Rail pressure was holding at 22k and even saw 24k momentarily under load up a hill, so that would eliminate and fuel restrictions, leaking injectors or weak pump.

[Diesel Krazy]

I finished more logging with Torque Pro on my other truck and now wondering if it is either bad FICM (Wouldn't it throw a code?) or maybe rust and junk plugging the injectors from when PO did the head studs? I would think if it was rust and junk in the injectors that the balance rates would be all over and in the + side due to trying to add fuel unless the restriction is not affecting it at idle? Any thoughts on this?

[Diesel Krazy]

Another thought on this is possible air ingestion in fuel. Normally this would cause hard starting and other symptoms, but dealer tech said vacuum on fuel port was 2hg which could indicate an air leak? One thing I noticed is at one stop on my way home which is on a hill and I coast quite a ways to the stop and it feels like it has a lot more power and more responsive when I take off from there. Going to try a clear hose on feed line and look for air bubbles. Seems like this or FICM going bad, but everyone says FICM rarely has problems.

Stay tunes for more results...

[rapidoxidationman]

The fuel system is under vacuum from the tank through the filter all the way to the high pressure fuel pump. If there's a leak in that vacuum system, it'll suck air in.

It's been said that a lift pump (and extra filtration)at the tank will help things live longer. It will certainly make any fuel line leaks obvious by pushing fuel out of the leaky area instead of sucking air in. Take a look at Kennedydiesel.com to see what he offers for a lift pump/filtration system. He's a member/vendor here and stands behind what he sells.

What kind of fuel filter are you using (OEM or aftermarket)? Lots of aftermarket filter cans use plastic housing instead of metal and have reportedly been prone to leak at the gasket. Even with the GM metal can, you've got to make sure the O ring gasket is properly in place or it'll leak.

A clear section of fuel line will be a good diagnostic tool. Let us know what you find!

(shamelessly stealing an image of a fuel pressure guage with and without a lift pump):


How's the truck run with a loose fuel cap? If the tank isn't venting properly you could be building up vacuum in the tank, which could lead to collapsed fuel lines and fuel starvation.

I'd be looking for another dealer tech... It doesn't sound like the one you've got now quite knows how the OEM system works.

[DmaxMaverick]

No problems with the brakes. It is even sluggish to rev the engine with no load. I just did some more logging to look at fuel rate and it looks like the ECM is holding back on fueling. Swapped MAP with other truck and seemed to help ever so slightly and was able to get 15psi if I floored it long enough uphill. It is a fueling issue for sure, just can't figure out why. Seems like something is telling it to limit fuel??? Rail pressure was holding at 22k and even saw 24k momentarily under load up a hill, so that would eliminate and fuel restrictions, leaking injectors or weak pump.

Do you have a boost gage? Or was this reported by the PCM, read on your scanner? 15 PSI is (minimally) respectable, if read from the gage, and the engine should be making power. NOT so, if reported via the PCM. It's barely above atmospheric pressure (1 BAR), at sea level (15-14.7=0.3 PSI, with a margin of error, may equal zero).

Check the wastegate for operation. If it's stuck open, or not closing for any reason, no boost, no power.

[Diesel Krazy]

The boost is corrected for atmospheric pressure. No gauge, but logging both trucks there is a big difference in boost. The other truck hits 22psi and spends a lot of time at 20+ under load. The truck in question briefly peaks at 10 - 15 but mostly sits at 5-9 while trying to get up to speed. I don't think boost is even an issue because no load revving of the engine should produce very little boost and it is noticeably unresponsive just trying to rev while in Park. My other truck revs much quicker and it is bone stock with 1 dead hole.

I should also reiterate that if I load level 4 on the PPE (120 hp?) Have not tried level 5, 2 or 3 give lesser improvements. it wakes it up to almost tolerable except off idle and low load or hills without having to push it hard to start making some power.

Didn't get time to work on it today due to GF and having severe back pain again. Probably will get back to it in a few days. Will keep updating the thread as I feel this is a somewhat unusual problem as it has no other symptoms besides being slower than a Mercedes 240D.

I tried to log the fueling rate, but the only thing I can get data on is PID ff125d labeled "Fuel Flow Rate" in units/hr (GPH I think?) and it hits around 3/4 of the good trucks numbers IIRC. I'm thinking that may be some other measurement or calculated estimate???

Who knows, just going to keep at it til I either get fed up or figure it out. TBC - School of hard knocks...Class Dismissed!

[DmaxMaverick]

This is curious. It's defueling to the point it has little power, like limp mode, but isn't throwing a related code. That leads me to suspect the aftermarket programmer. Try removing it (completely, physically, not just deprogrammed) and start at the beginning. If it is still that bad, it should throw some codes, without the PPE running interference. Or, as I've seen many times, that may be the problem, but they've almost all been the Edge units, and I've not seen this with PPE's.

[dually2002]

Maybe a worn turbo? Clearances to great at the impeller to create boost.

[Diesel Krazy]

I don't think boost is an issue as it should have more power that it does with no boost. My old 6.2 N/A truck has way more power. It is definitely a fueling issue. If I had a tech II or EFI Live to log the fuel rate I might be able to see something, but all I have available is Torque Pro which has very limited support on the DMax. Anybody have a list of PIDs for a LB7? I have some, but the fueling PID does not seem to work. I was able to get Fuel Rail Pressures working on it though.

[Kennedy]

I have a truck that I bought a while back with some preexisting problems. 02 2500HD LB7
The main problem is the thing can't get out of its own way. When stone cold, it barely responds to throttle input, barely comes off idle even when floored. As it warms up it gets better, but acts like it is limited to 1/4 throttle or less other than trans shifts late or kicks down on heavy throttle input.
It starts easily when cold and runs smooth with no unusual noises. No CEL ever.
No smoke and 11 psi is the most boost I have ever seen.
Almost tolerable it I load level 4 tune, but only with heavy input.
My bone stock LB7 3500 flatbed running on 7cyl has way more power. It has a valve train problem.. :-(
I have Torque Pro for logging, but it has its limits. Can't afford EFI Live yet.

New Fuel filter (Dealer tested for restriction in fuel system @ 2hg)
Tested Rail Pressure and it scales properly and Demand / Actual stay close.
Injector Balance is within spec. (Injector Age unknown) Not Making Oil!
PO did head studs 30k ago and Truck has 210k on it. (Said He couldn't afford to do the injectors then.
Checked engine harness connectors and 1 pin was pushed in a little, but no change.
Cleaned MAF and swapped with other truck, No change.
MAP Seems to scale fine ( Maybe I should swap with known good?) Cleaned, no help.
New Batteries and have tried another pair.
Currently set to stock and ECM was updated at dealer recently with no change in power.
The only think tech said was MAF not scaling to 450? I was able to get there but it took a while. Cleaned / Replaced made no difference.
Had an AFE intake on it, switched to stock and noticed a slight change, but not much.
Changed Trans Filter and topped off ATF as I heard that could affect it.
Exhaust is a 4" MBRP SS Catback system so no restriction there.
Not California model so no EGR.

I am at a loss why it refuses to give it fuel, like something is holding it back. Anyone nearby have EFI Live or a tech 2? I can only do basic checking and logging with Torque Pro and I can't afford to go back to the dealer or throw parts at it. I have spent many a night researching and testing only to come up empty handed so far. Maybe if I get a chance I will recheck or swap out MAP and even the AP? Sensor. I believe they both show the same with key on.

Any help solving this would be greatly appreciated...

I'm not sure why the previous owner would have done head studs just out of the blue? Odds are that when the injector lines were removed and reinstalled they dropped a bunch of rusty junk in the inlet bowls of the injectors and that is what is giving it fits. It just cannot deliver the volume that it needs to make HP.


Details here: http://www.kennedydiesel.com/docs/Du...0Corrosion.pdf

[Diesel Krazy]

I have thought about the injectors having crud in them from being worked on, but wouldn't balance rates be all over the board as they should not all be restricted the same? Also, why would it have significantly more power if I load a tune from the PPE? I really can't afford to do injectors right now, and don't like throwing parts at a problem unless there is a high probability of success in doing so.
I would assume if this is indeed the problem, I'm looking at new injectors and lines both?
Any real life symptoms described on one that was found to be badly plugged for comparison?

[DmaxMaverick]

The injectors and lines don't really get "plugged up", in the traditional sense. Debris from a R/R of the lines can contaminate them at the microscopic level, in the internal passages and valves.

I agree with your supposition, though. If it were caused by fuel line contamination, it would likely cause a significant balance issue.

Have you physically removed the PPE, yet?

[Diesel Krazy]

Yes, the PPE is a loader and is not physically connected except to load a tune. I had the ECM flashed at the dealer and the PPE was never reconnected after that, so that was not a factor. Currently running stock tune with nothing plugged in and it is so very slow...

[DmaxMaverick]

Was the PPE program unloaded, and returned to stock programming, BEFORE the PCM was flashed by the dealer? In any case, I suggest finding someone in your area with a similar truck that has a completely stock PCM, and swap it in.

Still, the problem points back to fueling anomalies that aren't causing the PCM to complain. A significant power loss should cause some data discrepancies, and DTC's. That is, unless the PCM does not interpret the data as being outside acceptable limits, or the limits are artificially adjusted, such as is commonly done with many programmers and power modules.

[Kennedy]

I have thought about the injectors having crud in them from being worked on, but wouldn't balance rates be all over the board as they should not all be restricted the same? Also, why would it have significantly more power if I load a tune from the PPE? I really can't afford to do injectors right now, and don't like throwing parts at a problem unless there is a high probability of success in doing so.
I would assume if this is indeed the problem, I'm looking at new injectors and lines both?
Any real life symptoms described on one that was found to be badly plugged for comparison?

Best I can say is I've seen it before. Texas truck as I recall. In for head gaskets came back a turd. Never the same. Had to use an Edge Juice on 90HP to even feel like stock. I believe the end result was dumping the truck.

Whenever I see a LB7 truck that does not perform properly, but runs otherwise fine and everything checks out fine it always comes back to injectors.

This will NOT show on balance rates.

[Diesel Krazy]

The ECM was put back to stock before reflash, I tried another stock ECM and even swapped out the FICM all with no change. Probably is plugged injectors which I considered early on, but would have thought that would have some other symptoms besides just low power. It sorta makes sense as it is totally non responsive stone cold when fuel is heavier and gets better as the fuel heats up and thins out. I may pull 1 or 2 injector lines to see if I can see any visible crud in them. I'm just afraid of opening a can of worms by doing that.

[DmaxMaverick]

I would not recommend pulling the lines, without fully intending to replace them, or give them a proper cleaning (ultrasonic). Removal alone can, and does, cause the contamination. Re-installation doubles the chance of that.

If warmer/thinner fuel seems to improve power, try going to the extreme. Run a 50/50 mix of #2 and kerosene, with about 2% 2-cycle oil (replaces lost lubrication). This will make the fuel about as thin as you'd want to run. It will have a lower BTU content, but that should not be noticeable if more fuel is allowed.

Another thing to try:
Supply the fuel from a fuel can, bypassing the OEM fuel filter assy (use a high volume inline filter). Position the can at or above engine level for minimal suction required. This will eliminate nearly all of the OEM fuel system, if there is a restriction (or collapsed fuel line) causing the issue. Keep in mind, the fuel return circuit will not return to the can, so most of the fuel from the can will be returned to the tank. Ideally, a fuel container can be placed in the bed, with a long hose to the engine compartment, suspended at the door handle(s), and over the mirror.

Have you eliminated the possibility of fuel contamination (gasoline, or other fluid)? The fuel can test will do this, if you haven't. A 50%+ mix of gasoline could easily cause this power loss.

[Kennedy]

Posts #23 and #27