Big Power Loss '03 5.9 HO

[bobinyelm]

2003 H.O, 5.9, 3500 Dually, 6spd Manual

On a recent trip towing my 8000 pound RV, I lost considerable power on an uphill section (narrow, 2 lane road) to where I only topped the hill in 1st gear (6spd manual) at 2900rpm w/ the pedal to the floor. VERY scary since there was a cliff on one side, and a 1000ft drop-off on the other on the very narrow rural mountainous Utah road. This was at 6500ft and maybe 100degF.

I attacked the hill at about 50 in 5th gear at about 2100rpm as usual, but ended up working down through the gears as the rpm sagged in each one until I was in 1st. Obviously if I couldn't have maintained rpm in 1st, I was out-of-gears and options.

The day before I was climbing similar hills (6% slope) at higher elevations (8500-10,000ft at 80degF) in 4th gear at light throttle setting-no problems and plenty of surplus power.

NO codes are set, and the truck starts, idles, and runs perfectly smoothly.

We just today plugged the Snap-On DRB Scanner into the truck, and found that regardless of throttle position beyond about 1/2 throttle, the MOST fuel pressure commanded was 18,000psi rather than the 23,000psi the tech said we should have seen at WOT. Actual Rail pressure followed commanded perfectly, so the problem is not downstream leakage, but that the system is failing to command max pressure at wide-open-throttle.

At sea level the truck "feels" almost normal except that advancing the throttle past approx 50% has zero effect on power created. It just kind of "boggs."

I replaced filters in the AirDog pump system in case we had a input fuel restriction, with no change.

We then unplugged the connector to the Fuel Control Actuator (FCA) on the injection pump, the tech saying that this should drive the system to MAX fuel pressure of 23,000psi + regardless of the actual throttle pedal position or engine rpm.

Commanded fuel pressure only went to 19,000psi, and rail pressure also went to 19,000psi. This was w/ the engine idling. The rpm didn't change, but the engine sounded more like a 2nd gen 5.9 engine (loud clatter) with the higher fuel pressure applied.

He recommended replacing the FCA and TPS (throttle position sensor), and if that didn't work, we were likely looking at anew ECU (master computer) unit.

Anyone offer any other ideas?

The rail pressure DOES rise to exactly match the "Commanded" fuel pressure, so I would think so far, we can't suspect the injection pump. It is making all the pressure asked of it

Does anything else affect the COMMANDED fuel pressure?

Until I know I can develop full power, I am reluctant to take my modest 8000 pound trailer into the mountains again. Only being able to crest hills at jogging speed in 1st gear is not a comfortable thing to do when there's no place to stop, or a way to back down to a safe place!

Thanks,
Bob

 

[GM Guy]

how many miles? Is the mechanic sure it isnt commanding without delivery, as in wore out CP3?

welcome to the site by the way!

 

[bobinyelm]

CP3 has 130k miles on it, as does the truck. Engine has 10k miles since total reman (prior owner let it overheat and scored 2 cyls).
All injectors were bench checked to 24,000psi and found to be perfect at O/H.
Engine runs exceptionally smoothly (zero shake at end of the long gearshift lever under all conditions).

The DRB Scanner shows both the commanded psi and the actual rail psi at the same time on separate lines so are easy to compare.

The actual rail psi is the same as commanded psi w/in 1-2% (the numbers bounce around about 1% or so), so the pump appears to be doing perfectly.

I'd think if the pump were worn, or the relief valve were venting, the rail psi would be LESS than the commanded psi.

I am trying to learn what sensors provide input to the ECU to create the command pressure, because THATS where the problem may lie (since the rail is exactly the same as command psi).

I DID replace the FCA and the TPS earlier tonight (just a bit ago, actually), and the vehicle "feels" peppier (could be wishful thinking), but I won't have access to the scanner until tomorrow if I go back to the tech's shop to hook it up.

Strange thing is that in upper gears at 1600-2200rpm, anything more than 1/2 throttle doesn't make more acceleration, but if you are AT full throttle, then you back off to 1/2 throttle, the vehicle surges forward (makes more torque/power).

If you are in a lower gear more than 1/2 throttle DOES cause good acceleration.

Does that tell you anything?

These perceptions are at sea level and not towing, BTW, since I live at 350ft elevation.

Unfortunately, I can't get back to hilly country to duplicate the experience (not that I'd want to-it sucked).

Thanks for the welcome.
You guys seem smarter than the at the other forum I used to hang out!

Thanks,
Bob

 

[littleboy]

What is boost pressure doing? It sounds like you have a map sensor going bad or a wastegate actuator stuck an making an overboost situation where the computer is cutting fuel to keep boost around 20psi.

 

[bobinyelm]

Good question on the boost pressure.

When I went to the shop, boost was my main thought. In fact, when I got to a safe place after the Utah incident mentioned, I looked for disconnected hoses or rushing air (from the turbo) under the hood, but couldn't see/hear any. That made me think of the MAP sensor.

Yesterday, the tech concentrated totally on fueling problems, and the only mention of boost pressure was that on the scanner, manifold showed 15psi at idle, which of course, meant zero boost as we were essentially at sea level, where normal pressure is that 15psi being read.

When I go back today/tomorrow (to see what changes, if any, were made by the addition of the new FCA and TPS I installed), I'll make sure that when we road test the vehicle again that we note manifold pressure under varying conditions to get an idea what the manifold pressures really are and that the turbo and associated plumbing is working as it should.

Thanks,
Bob

 

[THEFERMANATOR]

Find a shop with a better scanner and knowledge of common rail diesels. Unplugging the FCA is an invitation to other BIGGER problems, and anybody with a true understanding of the system would not do it. Sounds like his scanner isn't reading actual numbers which has been a major complaint of snap on scanners on many vehicles. If he is throwing parts at it without being able to duplicate the problem, then you are wasting money. From your description it sounds like the engine went into an engine protection mode which will reduce power, but not set a code(at least in a GM, not certain if the CUMMINS is the same or not). There are so many different things that can cause reduced power it is nearly impossible to track it down withut duplicating it or having a code to go off of.

 

[bobinyelm]

I hear you.

Problem is that this shop (and the sister shop next door run by a friend who mostly specializes in Powerstrokes) have the reputation of being the absolute best diesel guys in the 25mi area. Their shops are full of customers who got screwed elsewhere and went to them as their last hope, and seem to leave happy. The guy does transmissions (stock and performance) as well as Cummins performance mods and has a pretty wide following, for what that's worth.

Not saying they are geniuses; just perhaps that it's not easy to find good people.

I won't begin to relate my experiences with the O/H shop I used 300mi away that rebuilt my engine, and the R+R shop they used to do the pull and install (and the build-up of the long block).

They cost me THOUSANDS in related damages that they walked away from, and they were supposedly the best fleet O/H shop in Houston (as I was told). I live near Dallas, BTW.

I was told (who knows-I didn't) that unplugging the FCA at idle for a few seconds was relatively harmless as a diagnostic step. Live and learn I guess.
I'm a licensed aircraft technician, but not many diesels in airplanes, so I am at the mercy of outside help.

The fact that I make no power past 1/2 throttle may be a duplication of sorts of the problem. Obviously I can't go back to that road in Utah w/ my trailer in tow to exactly duplicate it (and given the pucker-factor wouldn't if I could!).

If I KNEW how a "normal" '03 manual trans behaved at greater than 1/2 throttle in 5th/6th gear at 1600rpm, I'd know if I am duplicating my problem (except for the altitude factor) or not
and could act accordingly.

A rolling dyno would be nice, though. Maybe that would give time for a more thorough duplication of the problem. Not sure if the 6000ft elevation vs SL here would present a problem in duplication.

I'd go to a Cummins shop, but they refuse to work on CRD Dodges for anything but mechanical work since they say they have NOTHING to do with the fuel delivery systems of Dodges w/ Cummins installed, and won't even look at such problems. FORGET the local Dodge dealership from all reports.

Of course, Cummins said they would have charged me $7500 just to have R+R'd my engine, with all necessary work and parts for my overhaul being extra when I was looking for a shop to do my engine. They estimated $13,000 for the basic re-build. That kind of priced me out of the market, though in retrospect, it might have come out better the first time had I paid that amount.

On the "plus" side, the tech I speak of was nice enough to hand me the new parts to install myself (and just replace them), so I am not yet paying labor charges. Sooner or later at least the TPS was bound to need replacement from what I hear, so I don't feel too bad about that $170 spent anyway. The FCA may have been a waste of money, however.

Any and all suggestions welcome, of course... your considered opinion (or even a guess) would be appreciated!
"Flying blind" sucks.

Regards,
Bob

 

[GM Guy]

For a little comparison on some 03 dodges.

my boss is running a pair of 2003 Dodge 3500 QCLB Cummins HO 6spd 4wd's, One a single wheel with the pickup box, the other a Dually with a flatbed. Comparing the driveability to his fuel plated 98 12 valve 5spd 4wd 11 ft flatbed chassis cab, the 98 has a bunch more "fight" in her. losing RPMs is a crime, she just doesnt want to give them up, and will fight hard to keep them. the 03 DRW is like a draft horse pulling all day. not super snappy, but when it comes down to it, she has it. It will lug to 1500, but once you reach 1500, it decides no more rpm loss, and the torque peak shines through. Boss jokingly says "if the squirrels under the hood reach a positive verdict on our request for power, we will make it up this hill! it does seem to have to request juice, basically give input of what you want (WOT) then possibly IAT, boost, etc is taken into account by the comp, and if the system is ok, the the fuel is given. no worse than aneroid on an older truck.

the SRW is a different animal. it sounds like a PSD when letting out on the clutch, as well as times at idle while rolling up to a stop sign. It is way snappier and gets great mpg, so he isnt sure if it is just different between SRW and DRW, or if the SRW has a chip or reflash.

but long story short, there is a delay, yes, but if you floor the DRW, it will give plenty. the SRW will give it all the time.

 

[bobinyelm]

Yes, that's how MINE was until the described incident (except I never ever needed to floor it-1/4th throttle was all I ever needed-I could always go one gear lower and 1/4th throttle was enough the way I drive).

On that hill in Utah, it couldn't hold rpm except in 1st gear WOT.

Now, tell me WHY!

Anyone?

Any more ideas?