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CharlieBuk · 11-06-2020, 06:38 PM

My 1997 Fleetwood American Dream has an issue and 3 different mechanics have looked at it with no results. It has a Cummins 8.3C Diesel and Allison transmission. The problem is that the issue is intermittent and there are no codes. About a year ago I was on a trip from Houston to Key West. About 3 hours into it the engine seemed to cut out for a few seconds. As I continued on my trip it got worse and worse where it would go into "Bad" mode for 15+ minutes. In "Good" mode I can cruise on the interstate at 65 mph at about 1600 rpm and it has plenty of power to climb hills. In "Bad" mode 65 mph is turning 1900 rpm and when you stomp on the gas the rpms go up but not much power. It continued this year on my Houston to Key West trip from which I just did. A couple of things I noticed. On my return trip from the keys the outside temperature was about 83 degrees and it ran mostly in "Bad" mode. As I went north on I-75 the sun went down and the temperatures cooled all the way to 52 degrees. It ran a lot better in the cooler temps and stayed in "Good" mode a lot. Maybe something is overheating? Also, it tends to run in "Good" mode while accelerating and as soon I get up to speed and let off the gas pedal it goes into "Bad" mode. I've changed fuel filters (twice) and the air filter. I've had the Allison transmission techs check it out and they don't think it is the transmission. Any advice would be greatly appreciated.

CountryB · 11-07-2020, 05:17 AM

I think a scan tool like the "Scan Gauge D" would help diagnose this. This unit is mounted in view (mine is on the dash) so you can watch it while driving. It displays four items at a time and also shows fault codes - if one sets.

You can monitor the engine (water and fuel temp, boost, etc.) while driving and see if anything is out of range when the Coach acts up.

153stars · 11-07-2020, 06:06 AM

Few things to check.
Cracked exhaust manifold .
Fuel lift pump leaking at gasket lets injector pump suck air .
Hidden inline fuel filter/strainer on or near frame rail. It can be hidden in bundle of lines/wire looms. Search posts here for this for years possible location. I know some were on Spartan or Freightliner chassis ,not sure years installed but this had cost many owners a lot of money in diagnosis and parts swapping.

jacwjames · 11-07-2020, 06:08 AM

You say that you had 3 mechanics look at it, did they do a scan of the ECM for codes.

oldmattb · 11-07-2020, 06:37 AM

The Cummins 8.3C is a mechanical control engine, so there is no ECM.

Has the small fuel filter on the passenger side of the engine block been changed? Word is, a lot of people miss this one.

Could it be crud in the fuel tank, sometimes blocking the outlet?

Loose or failing fuel lines to the engine? They are over 20 years old.

Intermittent injector or pump?

Good luck on a quick and inexpensive remedy.

Matt B

oldmattb · 11-07-2020, 06:42 AM

Two more thoughts...

I had a similar situation where our (previous) coach would not accelerate well - brake lights! The brake lights were on due to a trailer wiring issue, which activated the Pac brake.

That vintage of coach with an 8.3C, you possibly have a King Controls accelerator system. They can get glitch-y as they age.

Matt B

Ilvmygt · 11-07-2020, 06:56 AM

Quote:

Originally Posted by CharlieBuk

I noticed. On my return trip from the keys the outside temperature was about 83 degrees and it ran mostly in "Bad" mode. As I went north on I-75 the sun went down and the temperatures cooled all the way to 52 degrees. It ran a lot better in the cooler temps and stayed in "Good" mode a lot.

This statement is a little intriguing. There are a couple of temperature sensors in the air intake system. One would be ambient (before turbo) temperature (AT) and the other is charged air (after the Charge Air Cooler, i.e. CAC) Temperature. If the charged air temperature (CAT) sensor is bad and reading high it might explain the problem. If the Engine Control Module (ECM) sees a high CAT reading it will want to try to cool the charged air and would do that by increasing the RPM and holding the transmission in a lower gear (e.g., running at 65 mph at 1600 rpm and running 65 mph at 1900 rpm). The running in a lower gear is less stress on the engine and maybe more air flow across the CAC trying to lower the CAT.

The American Dream is a side radiator which means it has a hydraulic fan. Depending on how the fan is set up it it may or may not monitor the CAT. Some ECMs have the ability to increase the fan RPM to provide more cooling of the CAC if the CAT is to high, others use a “wax valve” which only monitors the radiator temperature.

CountryB suggestion of using a scan tool like the "Scan Gauge D" is a good idea. I would monitor the both the AT and CAT. If the CAT is reading high the sensor would need replacing. If the CAT sensor "bad" but not failed it would not set a code.

CountryB · 11-07-2020, 07:01 AM

Quote:

Originally Posted by oldmattb

The Cummins 8.3C is a mechanical control engine, so there is no ECM.
Matt B

I wasn't sure about that. It sounded like the OP had someone "connect" to the ECM since he said...

Quote:

My 1997 Fleetwood American Dream has an issue and 3 different mechanics have looked at it with no results.
It has a Cummins 8.3C Diesel and Allison transmission.
The problem is that the issue is intermittent and there are no codes.

But maybe that meant there are no codes because there is not an ECM.

FormerBoater · 11-07-2020, 07:10 AM

You state that you changed the fuel filters, did you change both of them?

Many here trying to help do not understand that your C8.3 is a mechanical engine...no ECM, sensors etc.

I think the Lift Pump gasket should be examined visually, if it is sucking air it is also leaking some diesel.

Cracked manifolds are easy to check on your Dream...open up the bed and look for soot on the manifolds themselves.

These engines just need clean fuel and air to run but anything that interrupts the delivery of either will cause the performance to degrade.

Good luck, usually these vintage C8.3's are trouble free.

BTW, one of the posts above mentions an in-line filter that is hard to locate....if your chassis is a Spartan you do not have one.

If it is a Gillig I have no idea.

153stars · 11-07-2020, 08:06 AM

I recently shared and read some old posts on hidden fuel filter trying to help another and am pretty sure, certain year Spartan had it hidden filter as well. That OP issue ended up being real bad exhaust manifold.

153stars · 11-07-2020, 08:19 AM

I snagged this excerpt from that share you may have to read it twice ,claimed hidden filter wasn't on Spartan it was
from link it may not be on yours but cost owner $5600 many similar stories ...dont get fixated on one item but.......

This happen to my brother dutchstar with the same Cummings. The same pattern or work and no fixes. He finally called his son back home and had him ask his mechanic Had he experience these problems before. Back up a little the call to Spartan chassis about any unknown filters they said no not in that model.

The mechanic back home call the service manager and told him exactly where the unknown filter is located. the tanks drop sterilized fuel was polished put back in the same scenario as above. His bill was little over $5600 total from all the different service areas he went to.

Caliber · 11-07-2020, 11:08 AM

Check fuel hoses and the fuel tank vent hose, after 23 years of soaking in fuel, the inside liner will become soft and collapse in, restricting fuel flow.

deandec · 11-07-2020, 11:51 AM

Releasing the fuel throttle after accelerating and it goes into the "Bad Mode".

Throttle position sensor.

Exhaust Brake activating and not releasing. (lubed regularly?)

Transmission downshifting quickly when throttle released.

Air throttle, if you have one, failing?

Radiator overheat shut down cycle activating?

CharlieBuk · 11-07-2020, 12:14 PM

Thanks to everyone for the replies and advice. It is on a Spartan chassis. I also learned 3 weeks ago that the exhaust brake line stripped out of the unit and the exhaust brake is "frozen". They wanted $3500 to replace the unit but we opted to plug it instead.

I've also had issues with the accelerator linkage recently as it was badly worn. My mechanic repaired it replacing one part. Is there a speed sensor somewhere that could be overheating or going bad that is causing the issue. It seems like small changes in gas pedal position affect "Bad" vs "Good" mode.

When I replace fuel filters I do both the large fuel separator at the rear of the engine and the Fram filter towards the front of the engine on the drivers side.

Whether it is in "Good" mode or "Bad" mode the transmission doesn't shift. At 65 mph it stays in 6th gear.

Based on the replies I'm not sure if I should be looking for a third, hidden fuel filter.

I'm not a mechanic but the mechanics have hooked up laptops to the connection under the dash to read codes (the ECM?). Allison also looked for codes and had a laptop running as we drove it down the road. Of course it wasn't going into bad mode as it was cold outside and hadn't been driven long enough (it can take 2-3 hours of driving before "Bad" mode shows up).

Any other ideas are welcome. I'll compile a list and get together with a good diesel mechanic to check all the possibilities.