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Old 01-10-2022, 04:54 PM   #1
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Cummins isc330 2001 no boost

I was driving my motorhome on the highway- and the boost went out after releasing the gas pedal-
no smoke - starts and runs fine. Mechanic says turbo is fine- waste gate is free, and we changed the waste gate actuator. We also change the fuel filters for the heck of it. still no boost- can not find any leaks and the inter-cooler and hoses look fine.
We are changing the mass airflow sensor tomorrow- i doubt that is the issue-
Its a very well maintained engine. I checked the air filter- very clean- and not very old. Any suggestions. Someone had mentioned the lift pump-
any other ideas- we are lost-
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Old 01-10-2022, 05:00 PM   #2
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Quote:
Originally Posted by gorlininc1 View Post
I was driving my motorhome on the highway- and the boost went out after releasing the gas pedal-
no smoke - starts and runs fine. Mechanic says turbo is fine- waste gate is free, and we changed the waste gate actuator. We also change the fuel filters for the heck of it. still no boost- can not find any leaks and the inter-cooler and hoses look fine.
We are changing the mass airflow sensor tomorrow- i doubt that is the issue-
Its a very well maintained engine. I checked the air filter- very clean- and not very old. Any suggestions. Someone had mentioned the lift pump-
any other ideas- we are lost-
I'd go under the dash and make sure wires at gauge are secure.
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Old 01-10-2022, 06:04 PM   #3
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Get a diesel mechanic instead of throwing parts at it.

How is it running with no boost, it should be a real dud on taking off and climbing hills.
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Old 01-10-2022, 07:49 PM   #4
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Get a diesel mechanic instead of throwing parts at it.

How is it running with no boost, it should be a real dud on taking off and climbing hills.
This.
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Old 01-11-2022, 12:48 PM   #5
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Put a scan tool on it and read what the engine computer says the boost is. (I just listed a Scangauge-D in the classifieds, and that will give you boost pressure...) If you are not seeing black smoke, and/or performance is not significantly degraded it may well be a gauge problem and not a boost/turbo one.
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Old 01-12-2022, 12:29 PM   #6
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Put a scan tool on it and read what the engine computer says the boost is. (I just listed a Scangauge-D in the classifieds, and that will give you boost pressure...) If you are not seeing black smoke, and/or performance is not significantly degraded it may well be a gauge problem and not a boost/turbo one.
Thank You - I run with a scan D - highest boost pressure is 2.7-no codes-my mechanic is now thinking fuel issue- changed the filters-
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Old 01-12-2022, 01:17 PM   #7
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Happened to us with our ISC. It was a cracked exhaust manifold. Made the sensors go whacky.
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Old 01-12-2022, 02:01 PM   #8
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Thank You - I run with a scan D - highest boost pressure is 2.7-no codes-my mechanic is now thinking fuel issue- changed the filters-
Fuel issue? What's his plan? You changed filters in 1st post....
You say engine runs great, starts up easy, no miss or slugglish acclatration?
Not sure your guy is spot on the issue yet as a fuel related issue will have other symptoms than just no boost pressure.
I'm not trying to beat up on your tech, only trying to help

You say it was running great and you released throttle pedal, and when pushed again, no boost pressure.....textbook boost leak.

So, my $$ is you have a boost PSI leak. You say in 1st post here that CAC hoses are all good, but I'm very suspect of them.
Take a closer look, at hoses/clamps and piping. A lot of motorcoaches use long 4" pipe for intake supply, a loose bracket, clamp etc.... can wear a small hole in pipe, most times in a hard to see place.

Sometimes a boost leak will show up as a small black soot looking streak on the pipe where hose connects

Also the air compressor intake pipe comes from the pressure side of CAC, inspect the pipe, it's like 1" in diameter and can be routed so thats hard to see a crack/leak

If this is a rear radiator chassis, it'll make this task a little tougher, but the CAC can be pressure tested as well...
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Old 01-13-2022, 08:40 AM   #9
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Thank You - I run with a scan D - highest boost pressure is 2.7-no codes-my mechanic is now thinking fuel issue- changed the filters-
I don't think this is a fuel issue, but when you step on the accelerator do you get any black smoke? When my turbo died, my ISC smoked up a storm, looked like I was 'rolling coal' like those jerks in pickup trucks do...

If no black smoke at all, then probably is a fuel issue. No fuel, not much exhaust gases, and no turbo action!
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Old 01-13-2022, 06:36 PM   #10
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ISC330 should get about 23 psi boost, 2.7 is way too low. I bet the OP wouldn't have the power to take off or climb hills.

First, check/test CAC and the sleeves for leaks. If not it, a new turbo is in order. My ISC350 has gone through the same scenarios, it's back to normal only after I put a new turbo on it.
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Old 01-14-2022, 05:35 AM   #11
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Just note that you won't see the higher (20+) boost numbers by just flooring it in neutral. You have to be running down the road under a heavy load to see those upper end boost numbers.
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Old 01-14-2022, 10:49 PM   #12
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Just note that you won't see the higher (20+) boost numbers by just flooring it in neutral. You have to be running down the road under a heavy load to see those upper end boost numbers.
I agree with this. You stated that it ran fine, was this while stationary, or have you tr
ied driving it. if it picks up and goes on the road then as a previous poster said then look at the gauge. I drove truck for 43 years and over 3 million miles and never had a boost gauge till I bought a motorhome. Good luck and let us know what you find.
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Old 01-19-2022, 10:18 PM   #13
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What happened t0o the OP? Must have solved the problem
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Old 01-20-2022, 01:55 PM   #14
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no not fixed- I found a new mechanic who will be here next week.
I will post the results, if it ever gets repaired

Thanks
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