No power climbing a hill from dead stop

[daldelta]

Current Situation
I have a 98 HR Imperial 40' motorhome with a Cummins mechanical 6CTA8.3 @ 325hp. My problem is no power on a hill from a dead stop. --I live in Tennessee in the hills, and do to property constraints when I back my motorhome out of my pole building I have to crank the coach hard to the left once my front end clears the building, I am also going downhill as I back out. After I have backed up as far as I can, to get out of my driveway onto the main road my wheels need to be cranked hard the opposite direction and climb uphill from a dead stop. I hold my breath every time because now when I bury the throttle the motorhome does not want to move. The engine is flat and I have no boost. After a few tries and much anxiety, it usually very slowly starts to move and I am able to get out of my driveway onto the main road. Once I am on the road I climb hills with no issues and seem to have plenty of power, my only issue with power is in the position stated above.

History- The engine has 48K miles and the only engine repair has been replacing the turbo charger. I do my own maintenance (not a professional) and changed the turbo myself after I was told by a Cummins dealership that it needed replaced. I had to be towed from my driveway to Cummings because on that occasion I could not get the motorhome to go up the hill. Cummings changed the waste gate and said it is a temp fix to get me home. After I changed the turbo it did not seem to help much, but now slowly the motorhome climbs the hill. It’s probably only a matter of time before I will need to be towed again. What can I do to get the power needed to get up the hill from a dead stop? What should I check, waste gate adjustment, fuel pump etc.? I do have a slight exhaust manifold leak, and I have adjusted the valves a couple of times, maybe I did something wrong there. When I changed the turbo I added a boost gage, and recently have seen as much as 20 pounds going uphill moving down the road. From my first observation it seems the crossovers and hoses/fittings are Ok and do not seem to be the problem.

Thank you for your responses and help
Dave

[WILDEBILL308]

What boost pressure are you getting when you are trying to get out of your driveway?
Bill

[Ivylog]

Remove the plug at the top/back of the injection pump. Turn the star wheel inside CW (looking from the back of the engine) two turns. This will put more fuel to the engine sooner with less boost pressure. Are you sure your tranny is in first gear. How many RPMs are you getting?
...........................................................................................................The plug is about here in picture below.
Another option to try is to let your engine run with the tranny in gear for 10+ minutes to heat the oil up so the torque slips more before trying to go up the hill.

[daldelta]

ScottG wrote:
Not unusual for that eng to crack exhaust manifolds, is that where your slight leak is coming from? If it's bad enough you may be missing a lot of boost.
(BTW, it's a "Cummins")

The leak is at the exhaust manifold gasket. I over torque the bolt when replacing the turbo. I did not have room to use a torque wrench . Extremely disapointing to find after all that work. I do not believe the leak has got a lot worse, I bought a high temp caulk that is used on high temp pressure pipes which worked OK but i believe it is peeling off now. I hate to think about removing that manifold again, so hard to get at all the bolts.
The leak may have become worse now, but directly after i changed the turbo and the leak was very minimal I still could not climb the hill much better. So I feel the main problem is elsewhere.
Thanks for your help

[daldelta]

adondo wrote:
It sounds to me like this only happens in the driveway, from your description.

I know Caterpillars de-rate until they're up to operating temp. I've been in places that I'm trapped in for a while until the Cat warms up enough to "give me some power" so I can get up a slope and escape a campground. (Such as some places in Colorado) The throttle isn't 40 feet of cable hooked directly, it's a rheostat mounted to the (probably Williams Controls) gas pedal, and sends a signal to the engine. (Drive by wire) You can't tell by the sound, the engine sounds normal enough, it's just "gutless" until the computer (ECM) decides it will run at full power.

If it's only happening in the driveway, then just wait until the coolant is up to temp, and your Cummins should operate normally. If it's doing that everywhere, then it's de-rating for some other reason, and a competent truck shop should be able to hook up to diagnostics and find out what's wrong. And, by competent shop, I don't mean the nearest RV dealer, I mean places that service Kenworth, Peterbilt, Freightliner, etc.

Yes, this only happens in my driveway at a dead stop. On the road it runs very well. I do have the drive by wire with the rheostat also, I am going to look into that because i did have an issue with the box one time. I sent it back to the manufacture and they rebuilt it. What i do not know is how my timing when i had that rebuilt meshes with my hill climbing problem. I think I will call that company back and see if that could be the problem.
I thought about the engine needing warmed up so a couple of trips ago I let it warm up a long time before leaving and it really helped. The last trip i did the same and it would not go, it slowly went up the hill. But after I was on the road and thinking about why warming it up worked the time before I had thoughts that my exhaust break may have been stuck on, which did happen once in the past. If it was stuck it started working again on the road.
I am sure I have a ECM but it is not the electronic engine, it is the mechanical version so I am not sure if they can plug in to check out the engine. I know i won't go back to Cummings after my bill for them to change out the waste gate, about the price of a new turbo.
Thanks for your input

[daldelta]

shaneperch wrote:
Is your turbo ok? how about head gaskets? Just an idea.

I believe the turbo is OK, I bought a brand new one and I have good boost (20pounds) when I am climbing hills on the highway. I have looked/listened to the engine and I do not have any visible leaks and the engine sounds very good when reved up, no unusual sounds. Thanks

[daldelta]

the bear II wrote:
What about building power with the brake on and then release the brake like they do in the tractor pulls ?

Good Thought, I am hoping to find a solution to why I am loosing power/boost, but if I cannot get it to start moving up the hill I certainly will try that.

[shaneperch]

Is your turbo ok? how about head gaskets? Just an idea.

[adondo]

It sounds to me like this only happens in the driveway, from your description.

I know Caterpillars de-rate until they're up to operating temp. I've been in places that I'm trapped in for a while until the Cat warms up enough to "give me some power" so I can get up a slope and escape a campground. (Such as some places in Colorado) The throttle isn't 40 feet of cable hooked directly, it's a rheostat mounted to the (probably Williams Controls) gas pedal, and sends a signal to the engine. (Drive by wire) You can't tell by the sound, the engine sounds normal enough, it's just "gutless" until the computer (ECM) decides it will run at full power.

If it's only happening in the driveway, then just wait until the coolant is up to temp, and your Cummins should operate normally. If it's doing that everywhere, then it's de-rating for some other reason, and a competent truck shop should be able to hook up to diagnostics and find out what's wrong. And, by competent shop, I don't mean the nearest RV dealer, I mean places that service Kenworth, Peterbilt, Freightliner, etc.

[ScottG]

Not unusual for that eng to crack exhaust manifolds, is that where your slight leak is coming from? If it's bad enough you may be missing a lot of boost.
(BTW, it's a "Cummins")

[the_bear_II]

What about building power with the brake on and then release the brake like they do in the tractor pulls ?