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Temporary loss of power


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03 Neptune 36PBD, 300 ISB Cummins with Focus toad.

In Upper Michigan, good weather, had an 8% downhill grade of 1500 feet, curve, then sudden construction stop at bottom.  When flagman released us had a loss of power where boost would not go beyond 20, engine load maxed out at 60%, and getting up the hills was very slow.  On the way downhill I had hard breaking, sharp turn, and applied the exhaust brake.

The oil pressure of 56, temp of 198, 2100 rpm, had not changed from what was normal yet the 'stop engine' light came on.  Stopped and checked all issues, had no water in fuel as had just filled in small city.

We continued slowly to the next campground and stayed for 2 nights.  meanwhile checked for lose hoses or clamps on the turbo and CAC.  CAC did not have crud on it and had been replaced 4 years earlier.

When we left that campground the boost and engine load was back to normal and 'stop engine' light was gone.  Had a great 386 mile trip that day as normal.

My questions are 'What can cause this?"

'What else could have been done to diagnose?"

"How to prevent in future?"

Thanks for the help.

Dale Noel

03 Neptune 300ISB Cummins

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This is just a SWAG, but perhaps the exhaust break stuck open.  Normally, I'd think it was air related, perhaps a blocked air inlet or filter, but not sure that would just go away.  Glad to hear you didn't have to change your plans much.

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There is a gauge on the air filter and I routinely keep the side grill clean.  The fuel filters are recent and the water separator bowl was without ANY water in it.

A great thought on the exhaust brake.

Now I will need more help.  I am a mechanical engineer but when it comes to vehicles I am a 'Parts Changer'  so I will go out, now that we are home for 5 weeks and find it.  What is the recommended lube for this?  I know I do not want to attract dirt.

 

Dale N 03 Neptune

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So was there any strange noises? Was there any smoke, was the transmission shifting in all gears? What was the RPM doing? How much fuel did you have?
One last thing, when was the last transmission service?

Temporary lack of power (low boost) FUEL, restricted exhaust, gear selection, torque converter not going into lock up (old trans fluid) plus givin you were using the exhaust brake could have not allowed it to return to “normal operation” 
I have a 2003 HR an on the dash it has a diagnostic switch to check for codes using the flash out of the check engine light, perhaps if your does try it an count any flashes.

if it does it again one thing is to pull over an try to see if you can remove your fuel cap..(a restriced vent can cause the fuel tank to pull in a vacum) which could account for the temporary loss o power. When the engine is off an walking by where the engine is can you smell any Diesel (perhaps if theres a leak you may be sucking air) not trying to be an alarmest but if your lift pump is starting to leak it will suck air which will cavitate the injection pump causing major problems… Read other posts related to lift pump issues.

All this stuff can cause a few poor nights sleep. 
All that stuff is what i would have looked at when dealing with a intermintent issue when i worked for Ford trucks.

One more thing, the actuator thats connected to the turbo which controlls the “vane operation” may have a issue. If the vanes are stuck in either direction can cause issues with either the low end at take off or the high end with lack of power at hiway speeds. 
Diagnosing intermintents can be difficult an costly, when im in the driverseat i use my “Assometer” along with all my other spider sences to try to shorten the lists of possibilities. Good luck an good hunting.

 

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I have replaced the old fuel caps with vented ones due to a problem several years ago. 

A friend was following and noticed nothing other than long time to get to speed.  Trans shifted like normal at the right times and the rpm was like it always was.  Trans was serviced Commins a few years ago, fluids changed at Maintenance session,

Silverleaf did not show anything different than what I see on it for the past couple of years except boost never went over 20 and % load never over 60.  The Neptune does not have a diagnostic switch but my Silverleaf shows everything as it happens.  Nothing unusual.

It seems like the exhaust brake is the most likely culprit and I'll get to it in a couple days.  We are home for 5 weeks then to SD, Havasu, Phoenix, TX, and then 6 mo in FL.

Thanks for all the suggestions.  I just now need to get to the exhaust brake.

Dale N 03Neptune

 

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I know this may be odd to most but check your fuel shutoff solenoid. I've had mine go bad in a way that let me start but no power. I could even shut down normally. Filters checked, changed, checked air intake and exhaust. My issue turned out to be a broken "arm" in the solenoid which "always" causes either no start or no shut off. In my case the bellows was able to open the fuel shutoff valve only a little and allow the closing of the valve to shut ft he engine down. No one that I've talked to ever heard of this. So, just thinking it's a good thing to check...

Good luck.

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Stephen, I had the same issue on mine, so not odd at all.  It would start and idle, but the accelerator did nothing.  It would just idle.  In the original post, he had a loss of power that after a period of time it returned and operated normally.  So, I did not suggest checking this.  This really sounds like the exhaust brake hung open for a while.

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23 hours ago, Dale N said:

A great thought on the exhaust brake.

Now I will need more help.  I am a mechanical engineer but when it comes to vehicles I am a 'Parts Changer'  so I will go out, now that we are home for 5 weeks and find it.  What is the recommended lube for this?  I know I do not want to attract dirt.

I use Tri-Flow on all of the points listed on the Exhaust Brake Lube Chart which I included below. If you have the Upgraded PRXB you include the base of the spring too.

There is also a YouTube Video showing how to lubricate the exhaust brake.

https://www.youtube.com/watch?v=E_wX98sHBpU

SuperLube-2.jpg

 

PacBrake Lubrication Chart.pdf

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Cummins uses a variable volume turbo on some engines.  I had a problem with this system while the ISL engine in my 2009 Dynasty was still covered by the Cummins 5 year warranty.  The Cummins shop replaced the turbo itself, the turbo tachometer sending unit and finally they figured out that the problem was with the variable volume unit.  Not too sure how it works, but I was told that it is not a waste gate but works in conjunction with the EGR system.  What happened was that on a long pull the engine would lay down and the boost would drop down to the 10 to 12 psi range.  Wow!  When you are on a 6 or 7 percent grade going about 36 mph in third gear and you lose power, you don't have much room to move onto the shoulder, if there is one.  This happened to me about ten times before Cummins  replaced the variable volume unit.  Whenever this happened I would stop, turn off the engine, wait awhile and then restart and go on my way.  It happened very randomly.

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