Intermittent Turbo Boost

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450slman

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May 2, 2021
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Selma CA
Hello all,

I have a new to me 1998 Holiday Rambler with the 24 valve Cummins. First couple times out, worked no problems. This week, however a problem with he turbo surfaced. It is not providing any boost intermittently. Generally, it seems to kick in sometime after it has been running for a while but not 100% of the time. Today it was nearly 30 minutes before it kicked in. Once it kicked in, seemed to work fine and power was restored. Any ideas?
 

jubileee

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Dec 17, 2013
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If you don’t have any turbo boost and your getting full fuel delivery, you’ll be filling the ditches and road up with smoke. I saw a wastegate come apart once and cause loss of boost, but it sure wasn’t intermittent.
Betting fuel delivery problem of some kind.
 

Gary RV_Wizard

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The turbo is driven by exhaust gases, so there are valves (gates) to guide exhaust to the turbine to drive the blades and then vent the exhaust back into the tailpipe. If anything sticks in there, the turbo doesn't spin or spins slower than necessary. The other possibility is inadequate lubrication of the turbine itself. It spins fast in an ultra-hot environment, so needs constant lubrication.

It would hardly be surprising if the turbo in a 23 year old engine is failing, so be prepared for an expensive replacement.

 

8Muddypaws

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My first thought was a stuck wastegate. Logically that's the only part that could be intermittent. Less expensive than the turbo.
 

450slman

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May 2, 2021
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Selma CA
My first thought was a stuck wastegate. Logically that's the only part that could be intermittent. Less expensive than the turbo.
What causes the waste gate to get stuck and how do I get in unstuck for good?

Took it for a drive tonight... started out just fine. Stopped to run into the store, restarted it, no boost.
 

8Muddypaws

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Probably have to replace it. I googled it and got dozens of replacements priced from just over $100 to nearly $300. I'd stick with a stock part.

looks like there were two designs used in 1998/1998.5 5.9 24 valve diesels.

The wastegate is what controls the boost pressure.
 

viceprice

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Maine
I have been around diesel motors but not knowledgable in the finer points of engine turbo management. I wonder if it would be worth the expense for an engine diagnostic test? Could the problem be with computer controlled issues and therefore easier/cheaper to fix? Again, limited knowledge on this front to even know the engine management for this year and engine. Is it computer controlled?
 

Gary RV_Wizard

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Cummins 24 valve go back to the fifties. I had a fully electronic 460 hp Cummins bought new in 1994
There were indeed Cummins electronic controls since about 1990, but not in a Cummins 5.9L "B" engine for highway use. The Cummins Celect and Celect Plus were used on the L10 engine (forerunner to the ISL) and M11 & N14 engines. The B engine didn't get an ECM until 1998.
 

jubileee

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Dec 17, 2013
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I wasn’t wise cracking. I thought some Holiday Ramblers got the Cummins 855 in that era. The high end high horsepower ones.
. I still say if the OP is losing boost and has full fuel delivery, it would smoke like a coal burner when boost is lost or down due to turbo bleed off or failure. Fill the ditches with smoke. Been down that road a few times. Fuel makes boost.
Fuel delivery problem. Fuel pump, fuel line, fuel filter, fuel something.
 

Robert K

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Jan 30, 2011
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519
when I was having a loss of boost it was the throttle position sensor.
Although this was on a Cat as Jubilee posted no black smoke.
 

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