Community Forums

primey · 07-01-2018, 05:37 PM

Hi all!

Long time listener, first time caller! I have had Monica (1998 Monaco Dynasty 40 ft... 8.3L ISL Cummins with a 6 speed Allison) for a little over a year. We have put about 5k miles on her and we recently went on a trip where we were having issues gaining speed.

The Symptoms:
It has a normal amount of power getting to 3rd gear. Beyond that, it seems to hang at the top speed for any given gear (3rd, 4th) and not wanting to shift. Going uphill it will stay at what seems to be the top speed for that gear with the throttle floored. The only time it will shift to the next gear is when we hit a downhill. At that point it has what seems to be fairly normal power until it reaches the top of that gear.

What I have tried:
After experiencing this issue for 40 miles I changed the fuel filter / water separator thinking the engine was starved for fuel. Unfortunately this had no effect.

Known issues:
The fuel cutoff solenoid has never worked very well on the coach. We end up using zip ties to keep it open. I have had this issue in the past one time and it seemed to be fixed by tightening the zip tie but that is not working in this scenario ( I have tried tightening it about 5 times to no avail)

I made it to my destination but I need to go home in a couple of days and I'm concerned about making it back. A case of beer and eternal gratefulness for any help at all. Thank you!

BFlinn181 · 07-01-2018, 08:03 PM

I'd suspect the transmission is the problem. You didn't specify which transmission you have, some models can blink error codes if you have the proper shift pad. You could start by checking the fluid level, but you might have to take it to an Allison service shop.

ThePowells · 07-01-2018, 10:07 PM

Welcome to the forum! I'm sorry that it took a problem for you to join us, but we hope that you will stay engaged after you have a resolution.

BigLar368 · 07-02-2018, 07:09 AM

Are you sure you only have one fuel filter? I would verify that first.

CaptBill · 07-02-2018, 07:22 AM

Quote:

Originally Posted by BigLar368

Are you sure you only have one fuel filter? I would verify that first.

Agree. I don't have a Cummins, but if I'm not mistaken, the did use a secondary, engine-mounted fuel filter on their engines. And a fuel restriction would prevent the engine from developing rated torque, and acceleration, which would cause the transmission to not shift to next higher gear. But that's just my thinking, and I am not a mechanic of any sort, for these engines.

windsorbill · 07-02-2018, 09:39 AM

Quote:

Originally Posted by primey

Hi all!

Long time listener, first time caller! I have had Monica (1998 Monaco Dynasty 40 ft... 8.3L ISL Cummins with a 6 speed Allison) for a little over a year. We have put about 5k miles on her and we recently went on a trip where we were having issues gaining speed.

The Symptoms:
It has a normal amount of power getting to 3rd gear. Beyond that, it seems to hang at the top speed for any given gear (3rd, 4th) and not wanting to shift. Going uphill it will stay at what seems to be the top speed for that gear with the throttle floored. The only time it will shift to the next gear is when we hit a downhill. At that point it has what seems to be fairly normal power until it reaches the top of that gear.

What I have tried:
After experiencing this issue for 40 miles I changed the fuel filter / water separator thinking the engine was starved for fuel. Unfortunately this had no effect.

Known issues:
The fuel cutoff solenoid has never worked very well on the coach. We end up using zip ties to keep it open. I have had this issue in the past one time and it seemed to be fixed by tightening the zip tie but that is not working in this scenario ( I have tried tightening it about 5 times to no avail)

I made it to my destination but I need to go home in a couple of days and I'm concerned about making it back. A case of beer and eternal gratefulness for any help at all. Thank you!

When was last time the allison filters were changed? Have you checked the fluid level?

Ilvmygt · 07-02-2018, 09:40 AM

On the Allison transmission you should be able to check the transmission fluid from the shift pad. With the transmission in Neutral press both the up and down shift keys at the same time. It takes several minutes for it to cycle then should flash the level (e.g., o K or L 1 etc.) Note the transmission has to be at least 135 degrees.

What does the transmission fluid look like? Is it burnt? If burnt you need to find out why.

Do you have any record as to when the last time the transmission filters were changed? If you are DIY person changing the filters and fluid is not too bad a job.

Have you tried to shifting the transmission with the shift keys? Does it shift when you do that?

In the end you will likely have to take it to an Allison Dealer to get it diagnosed.

deandec · 07-02-2018, 02:54 PM

Check your exhaust brake if you have one. The butterfly valve may be rusted partially closed and restricts your power. It should be lubed at least annually.

We have experienced similar but less pronounced problem currently. We also were using a wire tie on the Fuel Shutdown Solenoid.

There may be a positioning issue with the FSS rod. Too high or Too Low. Actually, I do not know more.

We just had the fluid and filters replaced about 7 months ago in the Allison so I suspect it has already relearned the process by now.

You also could look at the fuel throttle connector on your fuel pump. Ours was missing the cotter pin and retaining spring. That can leave you with a no power situation also.

MSHappyCampers · 07-02-2018, 04:10 PM

Hi !

Welcome to IRV2! We're sure glad you joined the gang!

I'm not a tranny guy and could only suggest that you be sure the transmission fluid is OK.

Good luck, happy trails, and God bless!

twinboat · 07-02-2018, 05:39 PM

Classic fuel starvation issue.

Check for another fuel filter. Some have screen type in the line, along the chassis rail.

Sent from my VS835 using iRV2 - RV Forum mobile app

veraken · 07-03-2018, 06:02 AM

Suggest you post this question in the Monaco Owners Forum where you might get some answers specific to your MH

BFlinn181 · 07-03-2018, 08:33 AM

After all the responses and further thought, I might have been too quick to blame the transmission. You said, "It has a normal amount of power getting to 3rd gear. Beyond that, it seems to hang at the top speed for any given gear (3rd, 4th) and not wanting to shift." At what RPM were you when you topped out in each gear? Was it at the shift point for that gear? I was blaming the Allison because you said it had normal power until 3rd gear, but a fuel starved engine or a partially closed exhaust brake could also create these symptoms.

I'm reasonably sure you have a second fuel filter, it may be tucked up along the frame rail between the tank and the engine compartment, you should trace the fuel line along the frame, I think you'll find it.

Gary RVRoamer · 07-03-2018, 10:42 AM

A 1998 Cummins definitely has a second filter - Cummins requires two filters on all their engines except a relatively short experimental period in 2003.

I note the original post refers to an 8.3L and ISL. Those are mutually exclusive - the 8.3L engine a a Cummins "ISC" engine and the Cummins ISL is an 8.9L.