Cat C7 starts, idles, but won't rev up in gear.

[Randy_A]

I have a 2005 Fleetwood Excursion on a Freightliner XC chassis with a 350 hp Cat C7. I drove it about 40 miles two weeks ago and it ran fine, accelerated good and ran 55-60 on the highway no problem. Yesterday I started it up tried to back out of my driveway and it would not make it up the small grade. It started easy, idles good, and will rev up when in neutral, but when in gear, forward or reverse, the throttle pedal goes down and nothing. I thought maybe it was fuel filters so I changed them this morning, no change. Any help would be greatly appreciated.

[Randy_A]

Brakes are all free. It rolls free on a slight grade.

[SCVJeff]

That happened on a friends Winne awhile back and it turned iut to be a frozen brake. Are you sure they are all free?

[shaneperch]

did you check the parking brake? My bus did that same thing and it was the parking brake fixed the wire and I was off and running. It was on my bus but I would think on a diesel pusher motorhome it would be the same thing. sounds like a sensor somewhere

[WyoTraveler]

Diesels require almost no fuel to idle. Clogged fuel lines and fuel filters would be my first suspicion. Once you power up a diesel will become starved for fuel and have no power. Of course old diesel tractors and swathers don't have all those flashing lights and codes. We see that a lot on farm equipment. Change the fuel filter as posted before. Then check fuel line for any clogs.

[Golden_HVAC]

With dragging brakes, the engine would rev up and 'try' to move the RV, but not move it.

His problem is it will only idle while in gear. It will go to a higher RPM while not in gear.

All temps look normal and no engine codes.

I guess you could open the engine cover, and look for the throttle. Can you move it safely while the cover is open and engine on? Remember the turbo will be very warm, and close by. If you can see the engine throttle moving while in neutral, then have someone driving it, while you try to move the throttle while it is in gear. This might not work at all on a new electronic controlled engine, but should work on one older than 2007.

Good luck,

Fred.

[Diplomat_St_Poo]

Our 2005 C-7 had similar behaviour a few years ago. Idled fine, would accelerate on level ground but would barely go uphill. . We did the same thing as you, changed fuel filters, still a no go. Ended up being the air filter. Replaced it and all was good.

[Big_Katuna]

You are correct; in limp mode I could till go 60. About half power.

Plus, in limp mode, what is causing it WILL throw a code.

Thats why I was thinking dragging brake. I had a front (drum) seize and had to rock it a few times. The shoe rusts to the drum after heavy rains. Never did it again.

[wallynm]

OP stated he changed the fuel filters. You wanting him to change them again.

diveman52 wrote:
When was the last time you changed the Fuel Filters?

[Randy_A]

1. Plenty warm. Normal on guage.
2. No codes or check engine light.
3. Air is up front and rear.
4. Fuel filters are new.
5. In limp mode you still have enough power to move the moho.

[rgatijnet1]

Sounds like it is receiving some information from one of the sensors that is putting the engine in to limp mode.

[diveman52]

When was the last time you changed the Fuel Filters?

[GlennLever]

I cannot rev my engine if there is not enough air pressure.

[Big_Katuna]

No code-check engine? Are you sure a brake isn't dragging? Maybe time to buy a Silver Leaf setup for your laptop.

[Ivylog]

I had a MH in my CG with the similar problem on a Cat engine. I forget now which sensor's plug (near the fan) was dirty and cleaning it solved his problem. May take hooking it up to a computer to see which sensor is not working correctly or try cleaning all of the two wire connectors you can get to.
A Cat/Allison will do the same thing until it warms up but doubt it's cold enough for it to do that. Worth giving it more time to warm up and see if it will accelerate after a couple minutes.