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atroph · 08-14-2019, 09:22 PM

2002 Fleetwood Bounder 39Z
Freightliner XC Chassis
5.9L 24V Cummins ISB300
Standard DP Allison Transmission (3000?)

Symptoms:

Atlantic to Pacific and back. Issue started on the way back about 3/4 of the way home in LA. The night it started I did get fuel at a gas station. I have been through 3 tanks since then also adding diesel kleen each time. I don't think the gas station fuel caused this problem.

Pulling out from a dead stop the coach will lag, and lag badly. Like it is choking.

If it is flat the coach will slowly reach 2k RPM and like a light switch the turbo will spool and the coach takes off. I have to manually hold first gear until about 2.7k RPM in able to get it to shift into 2nd at 2k and the same for the rest of the gears. It does just fine above 2k, but anything lower it is like there is a parachute behind me and the coach will even slow on a flat run.

Another weird thing is right at 2k the coach will shudder and surge in the transition period right at 2k. It does this both during accel and decel. All gears the same.

The engine noise and exhaust notes also seem vary greatly below 2k and above 2k. It is almost like the pacbrake is on during the low RPM runs. I can hear the turbo spool, but it doesn't seem to be making boost at low rpms.

I have also seen a couple of random CELs that seem to happen during high rpm high hill climbs and they last for a fraction of a second and go away. At the same time it cuts power. I don't think this is related but wanted to include it. Otherwise no CELs are set during normal cruising.

No smoke noticed.

Troubleshooting steps:

Changed fuel filter. Not too much debris in the cup. The cup was drained, cleaned, and filled with ATF. Filter is right next to the radiator and takes a cartridge type filter. The filter was changed prior to this trip.

I called Gaffney and asked about the pesky ISB inline filter on the frame rail. The tech could not confirm that it was part of my build. I looked, but need to hand over hand the fuel line to be sure it is not there.

Temporarily removed the air filter. Minimal change. Seemed to have better top end. A new one is on the way.

I cleaned the charge air cooler and radiator from both sides. While doing this I noticed that the exhaust downpipe had slipped out of the V-band clamp. I stuck my finger in the port and did see that the pacbrake was indeed open. I can not confirm that it is working properly though.

Inspected all intake and charge air couplers and no apparent leaks were seen. No hissing sounds unless I am at a high load/high boost situation.

ToDo:

I have the freightliner bluetooth diagnostic dongle ordered and will see if I can read the stored CEL codes and also see if the sensors appear to be reading correctly. Link: https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

See if a fuel pressure gauge can be installed on the injection pump. Under 2k it is a dog, above 2k it seems just fine, plenty of pickup and climbing power.

Rig a camera or get a helper to watch the engine while I am driving down the road to watch the wastegate and pacbrake.

I ran across this that seems very similar:
https://www.cumminsforum.com/forum/9...-low-rpms.html

Any assistance or ideas would be greatly appreciated!!!

Bob_C · 08-14-2019, 10:07 PM

Sounds like a lift pump on it's way out, starving the injector pump.....the fuel gauge will be the tell tale......my gauge is installed on the injection side test port on top of fuel filter canister........that way it test's the filter and the pump...the condition is also known as dead pedal

broadrun · 08-14-2019, 10:56 PM

Those were the exact same symptoms that I had in my F250 with a 6.0L Powerstroke Diesel.

It turned out to be a bad injector. Replaced it and all has been fine.

Probably not your issue but wanted to mention it. Is there a way you can so a buzz test on Cummins injectors like you can on a PSD?

RichKimball · 08-15-2019, 08:07 AM

A couple of things to check other than what you are planning that I had with my 5.9 in my 39Z.
1. Change out the lift pump to an Airdog or some other aftermarket pump. They are easy to change, almost plug n play.
2. Check the air pump hose that runs along the passenger side of the engine. They seem to develop holes especially on the underside where you can't see it. I replaced mine from stock at an O'Reilly's where they just matched best they could. Much cheaper than a Cummins part.
3. MAP sensor on intake manifold. After I changed this the pickup from stop was much improved. I also purchased this at an O'Reilly's.

Good luck.

atroph · 08-15-2019, 01:23 PM

Quote:

Originally Posted by bob caldwell

Sounds like a lift pump on it's way out, starving the injector pump.....the fuel gauge will be the tell tale......my gauge is installed on the injection side test port on top of fuel filter canister........that way it test's the filter and the pump...the condition is also known as dead pedal

Thanks!

I was digging around in QuickServe and apparently after codes and restrictions is the lift pump in the troubleshooing tree. Code reader will be in tomorrow and hopefully it'll pop the stored but not active codes. I'll also work on hooking up a FP gauge. It seems I may need a special fitting to tap into the lines (banjo to schrader). They seem common enough to find online.

Quote:

Originally Posted by mevman

A couple of things to check other than what you are planning that I had with my 5.9 in my 39Z.
1. Change out the lift pump to an Airdog or some other aftermarket pump. They are easy to change, almost plug n play.
2. Check the air pump hose that runs along the passenger side of the engine. They seem to develop holes especially on the underside where you can't see it. I replaced mine from stock at an O'Reilly's where they just matched best they could. Much cheaper than a Cummins part.
3. MAP sensor on intake manifold. After I changed this the pickup from stop was much improved. I also purchased this at an O'Reilly's.

Good luck.

I've been reading up on FASS, Airdog, and Raptors. I tend to get OEM parts as often as I can. Are they that much better than factory parts?

I'm not sure what you mean by air pump hose. I'll give all hoses a thorough inspection on that side and also familiarize myself with the lift pump since it lives on that side and how much of a job it'll be if I have to replace it.

Are you referring to the air compressor inlet hose?

https://www.ebay.com/itm/Cummins-HOS...-/142180082019

In the link I shared above it was the MAP sensor that corrected the problem. They seem relatively inexpensive and easy to change.

Thanks for the input!

twinboat · 08-15-2019, 01:54 PM

I don't see how the lift pump would cause low power below 2000 RPMs, yet give you good power at higher RPM situations, where more fuel is needed and used.

Fuel is limited at lower RPMs to decrease smoke. If the sensor that controls that is bad, it may be limiting it to much and will do what its doing.

RichKimball · 08-15-2019, 02:00 PM

Quote:

Originally Posted by atroph

Thanks!

I was digging around in QuickServe and apparently after codes and restrictions is the lift pump in the troubleshooing tree. Code reader will be in tomorrow and hopefully it'll pop the stored but not active codes. I'll also work on hooking up a FP gauge. It seems I may need a special fitting to tap into the lines (banjo to schrader). They seem common enough to find online.

I've been reading up on FASS, Airdog, and Raptors. I tend to get OEM parts as often as I can. Are they that much better than factory parts?

I'm not sure what you mean by air pump hose. I'll give all hoses a thorough inspection on that side and also familiarize myself with the lift pump since it lives on that side and how much of a job it'll be if I have to replace it.

Are you referring to the air compressor inlet hose?

https://www.ebay.com/itm/Cummins-HOS...-/142180082019

In the link I shared above it was the MAP sensor that corrected the problem. They seem relatively inexpensive and easy to change.

Thanks for the input!

The factory lift pump is not a good choice...and yes...the aftermarket ones are far superior. A note of caution though I forgot to mention. The ECM controls the pump, and it was recommended to power the pump through a relay tied to battery power and have the ECM control the relay. Some reported they fried the ECM due to excess current draw.

That could be the hose pictured. It runs from the air pump down the left side near the back of the engine under the VP44 IIRC. If it ruptures, you will have poor performance and very low boost.

The MAP sensor replacement gave me a little more get up and go from idle.

atroph · 08-16-2019, 02:18 PM

Ok here is what came up on the scanner.

I cross referenced the code from here:

https://www.google.com/url?sa=t&sour...wFD8ig26eGy4V8

Looks like there is some sort of fuel issue. I'm going to have to read up on this one.

Pandion · 08-17-2019, 09:02 AM

I had very similar symptoms a few months ago with my 1999 Freightliner XC/Cummins ISB 5.9 275hp coach. Absolutely terrible off the line, then a surge of power at about 1700-2000 rpm. Canceled a weekend trip. Had a CEL and pulled the code with my Scangauge-D. I'll try to find the exact code, but it had to do with the intake manifold pressure sensor or wiring. Started tracing it, and found an aftermarket "tuner" box! It was wired in between the manifold sensor, Cummins ECU and another wiring loom connector. But the key was that it was inserted between the Cummins/Freightliner connectors and the components that they connected to. So I removed the aftermarket box, cleared the code, took it out for a test drive, and all better! Nothing better than a $0 repair. It does seem to have slightly less power once the turbo kicks in, but the whole engine runs much smoother and power this summer going up grades from Phoenix to NE AZ was no real problem. You might want to look over your engine compartment to see if you have some sort of aftermarket widget messing up your injection. I'll see if I took pictures or saved the codes and report back.

Pandion · 08-17-2019, 09:15 AM

A few other quick notes. Going by the maintenance records, my coach had been owned previously by at least two other owners with no mention of this box being installed in the records going back to 2003. Probably by a third owner that regretted getting "only" 275 hp.

I did find the tuner company online, but they no longer made this box and didn't have any tech details online. I can live without it.

My exhaust brake was seized and non-functional when I was having this issue.

atroph · 08-18-2019, 10:21 AM

Quick question, Is the lift pump before the filter or after? Meaning can I tap into the filter housing and get a good fuel pressure reading?

Unfortunately I do not have any ports to easily tap in to. However there is a water sensor in the cartridge housing that is also labeled as upstream fuel pressure. Can I remove the water sensor and test fuel pressure here?

Edit: added pics

RichKimball · 08-18-2019, 10:48 AM

I don't think I would recommend removing the water sensor. There are lots of available kits on the market for fuel pressure monitor.
On my 6.7 ISB, I know that any problem associate with water in fuel will cause an engine STOP.

atroph · 08-18-2019, 11:37 AM

I tapped into the water sensor port and got 0 on the gauge. I can hear the pump running after bumping the engine over.

I can also see an increase of fuel flow by pushing the water drain valve with the pump running vs it off. Fuel appears to be moving, but not making any pressure.

Is the filter/separator before or after the lift pump?

In this video at around 8:30 it appears that he is tapping off fuel pressure on the right side of the filter (similar to what I have installed). I think this is the after element port that would give you filtered pressure. This would also lead me to believe that the filter is supposed to be pressurized at whatever the operating pressure should be.

https://www.youtube.com/watch?v=lxSrIFHq3CQ

Am I correct?

atroph · 08-18-2019, 11:58 AM

So looking at the manual it appears that the fuel filter should be pressurized at whatever the running pressure should be, and the pressure is tapped at the left of the filter which is the input side (same as water sensor).

This appears to be a similar configuration just like the dodge in the above video. I'm guessing that freightliner moved the filter from next to the lift pump to the rear of the coach for easier access to the filter.

I'm going to hand over hand the fuel lines and look for any other type of strainer or filter. If nothing is found looks like I'll be ordering a lift pump.