sfctrucker

No Acceleration From Dead Stop

26 posts in this topic

1996 Safari Continental, 330 HP 3126 with 6 speed Allison Auto.

From a dead stop going up an incline motor home will NOT accelerate in first gear, will not accelerate in reverse either going up hill.

If you get a running start, getting the RPMS up to 900 or so, the Turbo will kick in and it climbs hills no problem.

HISTORY: MH would not start, changed Hi and Low speed engine sensors, would then crank and run, but with NO power at all.

Changed turbo, old one was cracked in the waste gate seat and stuck closed. Runs decent on open road has sufficient power but lacks

climbing power I think.

Possible turbo out of adjustment?

HELP

Chuck

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Chuck,

Welcome to the FMCA Forum.

Does this happen when the engine is warmed up as well as when cold?

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It is slightly better when engine is warmed up, but still not good at all. If you were behind me you would be mad as H***.

MH was completely serviced oil/air/fuel filters (All NAPA) about 700 miles ago, made no difference.

Chuck

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Check that the new turbo is indeed operating. Pull the air intake hose off at the turbo and make sure it is free to turn. Do this with engine off. You can spin the blades by hand. Also, make sure your exhaust clamps are tight and the exhaust is not cracked or leaking anywhere, as this can contribute to your problem.

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Hi Chuck,

Welcome to the FMCA Forum!

My thoughts on the possibilities: Restricted exhaust system, Restricted air intake-filter or hose, Leak in the high side output from the turbo to the intake manifold, bad intake manifold gasket, leak in the CAC. Poor fuel pressure-weak lift pump or injector issue.

Also check the intake hose going to the air compressor of a hole.

Rich.

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Add exhaust brake stuck shut or mostly shut to the list.

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sfctucker,

How long has it been since the fuel filters have been changed? My unit would buck and snort at low speeds and would buck when I got up to speed and would try to accelerate. Changed both filters added strong additive and haven't had a problem since.

Herman

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Thanks for all the suggestions:

1. Pulled out the air cleaner, started it up and tried a hill from a dead stop. NO Change

2. Put air cleaned back on and pulled the exhaust brake, muffler, and pipes. Put on 6 ft of flex pipe, made no difference except being loud.

3. Have no way to test fuel pressure.

4. Turbo does spin freely, I'm sure it works as I'll get 18-20 pounds of pressure when it kicks in fully at about 13-1500RPM depending on the gear.

When I'm trying to start out on an incline its like I get no throttle response, she idles fine, if the incline is not too bad, the idle will start the MH moving and if I can get up any speed at all and get the rpms up to 900-1000 the turbo will begin to show pressure and it will start to accelerate, once it gets going and the rpms are 1300 or more she does fine and away we go.

What I don't know is what controls the turbo pressure??

Is there a turbo boost control sensor?? or something like it.

Is there any adjustment on a turbo, or could they have put on a wrong turbo. It came from CAT and looked identical to the old one.

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Take it to any Caterpillar dealer and have them check for codes-- sure beats guessing.

Could be a crank angle sensor, low fuel pressure, etc.

Let us know what they find.

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A possibility, Boost pressure control swing valve/poppet valve does not close, causes low turbo boost, but do you get black smoke.

Not sure you turbo is so equipped.

Your boost pressure reading is on the low side, think 28 to 30 psi. in most cases.

Did you check the air supply hose for the Air Compressor? the compressor air is supplied from the turbo boost output. Often connected at the intake manifold by a hose that looks like a water cooling hose.

Rich.

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Actually 30 PSI is plenty of pressure. Most engine makers state boost in column inches of HG. PSI is very close to TWICE column inches of HG.

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sfctrucker,

Be sure and post what the problem was and what was done to correct it when you have the dealer check the codes.

Herman

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sfctrucker,

I have a 2006 330 ISC Cummins and what you claim may be the nature of the beast (diesel). I know because near my home I have to climb a hill from sea level to 410 feet at 7.5 percent grade. It is slow starting out and before I get to the top I'm finally getting up to speed only to have to slow down again and make a turn on the street I live. Not only this coach but the one I owned before this on the same result. Until the turbo gets spinning good it's make no sense to floor it as the added fuel will not add power until the boost from the turbo kicks in.

Your boosts of 18 - 20 seems a little low as mine goes over 25 to about 28. You can check with your dealer for the spec for your engine. One thing I did for the last coach is get a straight flow through muffler, restriction fitting for the turbo and stepper plate for the injection pump. This was on a 93 240 IBT Cummins so you may or may not find a way to boost it any better. I know that what I have now can only be boosted with a tuner chip or have the ECM reprogrammed.

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Thanks for all the comments guys, For the gent from Washington State, this is much worse than the nature of the "Beast". I'm a retired truck driver, and when I purchased this old girl we went to NC in it from Syracuse NY and I was very impressed with its power in every way. There are two long pulls on I 81 both in PA, and one on I 77 in NC. This thing pulled all of them very well, it didn't overheat and I topped all of the mountains at over 50mph. The turbo boost then was maxing out at over 30.

MY 2006 IHC with a 600hp Cummins ISX and 18 speed Eaton couldn't do that unless I was empty. Then the weights would have been about the same. SO That said, IT is going to ta CAT dealer once I get back from Fl, Have reservations to go to some of Spring training Games fro the Yankees in Tampa. Will likely take it to Atlanta as the only other CAT dealer in the area is in Ashville NC but there is a 4000ft mountain in the middle and I don't feel like fighting it.

Will post results when it is fixed.

Thanks guys

Chuck

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Chuck, while you have it in for service and not knowing the mileage on the engine; you might want to have the valve tappets reset.

Forgot to mention that the turbo on my unit kicks in between 1100 and 1200 RPM and rapidly increases from there.

Rich.

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"What I don't know is what controls the turbo pressure??


Is there a turbo boost control sensor?? or something like it.


Is there any adjustment on a turbo, or could they have put on a wrong turbo. It came from CAT and looked identical to the old one."



There is a possibility that there was an restricting orifice in the line to the waste gate that was removed when the new turbo was put in. That would explain why old turbo was making over 30 psi. Also a stuck closed waste gate would make more boost not less.


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It is all to do with gearing and your torque converter lock up until you have enough RPM to make power to slip converter and drive rear wheels

mine sucks when I have to start on hill or if I get slowed down to much behind some one else or bad road makes me.

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For those who followed this post:

It has been Fixed.

Problem was with the high pressure fuel pump, and a pin hole in the incoming fuel line.

Replaced pump, high and low speed sensors, some o Rings and a fuel line...

ALL IS GOOD NOW!!!!!!!!!!!!!!!!!!!!!!!!!!!

See you on the road.....

Chuck Willis

US ARMY Retired

1996 Safari Continental w/white tiger on the back.

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Thank you Chuck as we all know, not enough fuel will make less power.

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I have nearly the exact same issue with an older Detroit 8V92 and no one has ever been able to figure out why I am not producing the boost that I used to. Even when it gets "wound up" I still see less boost than I used to. The fuel pressure is correct where you would measure fuel pressure, the turbo is good and the filters are all good.

Could you tell me a bit more about what exactly you found to be a problem? How did someone diagonsis this problem? Where is the located that found the problem? I will go anywhere to get my power back!

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For those who followed this post:

It has been Fixed.

Problem was with the high pressure fuel pump, and a pin hole in the incoming fuel line.

Replaced pump, high and low speed sensors, some o Rings and a fuel line...

ALL IS GOOD NOW!!!!!!!!!!!!!!!!!!!!!!!!!!!

See you on the road.....

Chuck Willis

US ARMY Retired

1996 Safari Continental w/white tiger on the back.

BillAdams

Posted Yesterday, 08:53 PM

I have nearly the exact same issue with an older Detroit 8V92 and no one has ever been able to figure out why I am not producing the boost that I used to. Even when it gets "wound up" I still see less boost than I used to. The fuel pressure is correct where you would measure fuel pressure, the turbo is good and the filters are all good.

Could you tell me a bit more about what exactly you found to be a problem? How did someone diagnosis this problem? Where is the located that found the problem? I will go anywhere to get my power back

Bill, looks like Chuck covered everything except the repair shop.

A pin hole in the fuel line running between the lift pump and the injector pump is a new one for me.

Wonder if there was fuel leaking out the pin hole or if the injector pump demand minimized the fuel loose under idle speed. That problem would be a difficult one to find.

Think the only way would be a vacuum or pressure test of that section of the fuel line to be sure of its integrity!

Know now to keep in mind the condition of the fuel supply line running between pumps and age of the coach.

Rich.

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Shouldn't a lift pump be supplying more volume to the main pump than is being used? Thus, there would be pressure in that line? So, the only way a pinhole would cause lack of fuel, would be to leak it out?

How could it suck air into a hole that has positive pressure inside of it? Or am I mistaken, and there is still vacuum AFTER a lift pump?

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Shouldn't a lift pump be supplying more volume to the main pump than is being used? Thus, there would be pressure in that line? So, the only way a pinhole would cause lack of fuel, would be to leak it out?

How could it suck air into a hole that has positive pressure inside of it? Or am I mistaken, and there is still vacuum AFTER a lift pump?

You are correct. Suction side includes tank pickup, fuel line from tank to primary fuel filter/water separator, separator itself and line from separator to lift pump.

The lift pump provides pressure, so the line from it to secondary fuel filter, secondary filter itself and line from secondary filter to engine/injector pump is pressurized. Pressure varies by engine/injection system.

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You are correct. Suction side includes tank pickup, fuel line from tank to primary fuel filter/water separator, separator itself and line from separator to lift pump.

The lift pump provides pressure, so the line from it to secondary fuel filter, secondary filter itself and line from secondary filter to engine/injector pump is pressurized. Pressure varies by engine/injection system.

So, as OP stated the hose was NOT leaking, how did replacing a hose that is pressurized, with a pinhole in it, fix his problem?

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