400db Cummins 6CTA 8.3 Hangs at 1,400 rpm’s

[JoeV]

Issue with my 2001 400db. When throttling up Starboard engine the rpm’s stall at 1,400 even at full throttle. Throttling up the port engine does not effect or change the condition. After a few minutes the Starboard rpms start to climb with a surge based on the fact that the throttle is set to maximum. This happens in both manual and when using the synchronizer. When in idle the engines both throttle up with no issue to a max of 2,400 rpms.

Fuel filters all changed out, flow is good. Transmission needed service with a new heat exchanger and solenoid. Also had exhaust mixing elbow replaced.

So far nobody has been able to figure out why it’s doing what it’s doing.

Has anybody experienced this? Open to any and all suggestions. Thanks guys.

HELP!

 

[PartnerShip]

Check your aftercooler and all connecting hoses/pipes.

 

[ZZ13]

Turbo may be bound up. Pull off air filter and see if you can spin compressor blades freely by hand

 

[mquiet]

Turbo. Start by following ZZ13

 

[my3sons]

JoeV, Who are the nobody's that haven't been able to figure this out? Diesel Mechanics?

Did all this start right after the tranny service and heat exchanger replacement (assume HX is the gear cooler?) and assume this is all on the starboard side, including the mixer elbow?
Black smoke when underway trying to come past 1400 rpm?

 

[JoeV]

Hi Mark and Karen,
Thank you for answering. This all started after the tyranny work and new gear cooler heat exchanger. When the yard did the service they noticed a leak in the mixing manifold and replaced it. They broke one of the bolts and needed to remove the turbo and the housing to extract the broken bolt and tapped a new one. After the very expensive service and replacement parts I took her out and had the problem and also found that the leak wasn’t repaired. Black smoke wasn’t noticeable but the engine hangs at 1,400 -1,500 even at full throttle. That’s when I called in an independent mechanic to scope it out and so far he met a dead end. Thanks

 

[JoeV]

Check your aftercooler and all connecting hoses/pipes.

Will do thanks.

 

[JoeV]

Turbo may be bound up. Pull off air filter and see if you can spin compressor blades freely by hand

Thank you. We will check it out. The yard mechanic may have damaged it.

 

[mquiet]

Questions some Cummings guys might know and will help. Is 1400rpm the limp mode rpm for these engines and do you have a computer connecting them? My Cats will notice when one engine is not running and put the boat into limp mode. I am wondering if your engine is stuck in limp mode due to some feedback it is receiving. Or it is turbo.

 

[quality time]

You'd see lots of black smoke during acceleration if the turbo was sticking. Sounds like your losing boost so I'd double check all of the turbo connections since it was removed.

 

[ZZ13]

Questions some Cummings guys might know and will help. Is 1400rpm the limp mode rpm for these engines and do you have a computer connecting them? My Cats will notice when one engine is not running and put the boat into limp mode. I am wondering if your engine is stuck in limp mode due to some feedback it is receiving. Or it is turbo.

Your engines are totally mechanical. There is not a computer chip anywhere. So there is no limp mode. If you aren't getting full power it's either air restriction, fuel restriction, or lack of compression. I highly recommend adding boost gauges to help tell the full story along with the existing temp, voltage and oil pressure gauges. Some also add Exhaust temp (EGT) sensors/gauges.

 

[mquiet]

Your engines are totally mechanical. There is not a computer chip anywhere. So there is no limp mode. If you aren't getting full power it's either air restriction, fuel restriction, or lack of compression. I highly recommend adding boost gauges to help tell the full story along with the existing temp, voltage and oil pressure gauges. Some also add Exhaust temp (EGT) sensors/gauges.

Boost gauge would help. Do these engines have a booster sensor?

 

[ZZ13]

Boost gauge would help. Do these engines have a booster sensor?

No it doesn't. But there are several plugs on the air intake that can be removed to add a boost port and a gauge at the dash. You just need to run about 25' of 1/8" od air hose between the port and the gauge. That's what I did. Which I learned how to do from Mark (My3sons). He's smarter about all this diesel stuff than me. I learn from him.

 

[Strecker25]

I just added boost and egt with the ISSPro gauges to our cats. I love having the data right in front of me, especially the EGT to compare between engines.

 

[my3sons]

Hi Mark and Karen,
Thank you for answering. This all started after the tyranny work and new gear cooler heat exchanger. When the yard did the service they noticed a leak in the mixing manifold and replaced it. They broke one of the bolts and needed to remove the turbo and the housing to extract the broken bolt and tapped a new one. After the very expensive service and replacement parts I took her out and had the problem and also found that the leak wasn’t repaired. Black smoke wasn’t noticeable but the engine hangs at 1,400 -1,500 even at full throttle. That’s when I called in an independent mechanic to scope it out and so far he met a dead end. Thanks

Sounds like you have had at least two different mechanics looking at it so not much I can add. The other suggestions here are good and the fact that the problems started when they took things apart lends credence to the suggestion that maybe they didn't get the charge air hoses or pipes hooked up correctly. It also sounds like the turbo could be hanging as someone else suggested. Not sure if something happened to it when it was removed to drill out that screw. Either way though, you should be seeing black smoke and you are not. Assume your mechanics have checked all the easy stuff like checking the hoses, checking the turbo bearing, throttle, etc. Were it mine, I would hook up a temporary boost gauge and see what it says. Good luck.

 

[JoeV]

Sounds like you have had at least two different mechanics looking at it so not much I can add. The other suggestions here are good and the fact that the problems started when they took things apart lends credence to the suggestion that maybe they didn't get the charge air hoses or pipes hooked up correctly. It also sounds like the turbo could be hanging as someone else suggested. Not sure if something happened to it when it was removed to drill out that screw. Either way though, you should be seeing black smoke and you are not. Assume your mechanics have checked all the easy stuff like checking the hoses, checking the turbo bearing, throttle, etc. Were it mine, I would hook up a temporary boost gauge and see what it says. Good luck.
View attachment 93209

Sounds like you have had at least two different mechanics looking at it so not much I can add. The other suggestions here are good and the fact that the problems started when they took things apart lends credence to the suggestion that maybe they didn't get the charge air hoses or pipes hooked up correctly. It also sounds like the turbo could be hanging as someone else suggested. Not sure if something happened to it when it was removed to drill out that screw. Either way though, you should be seeing black smoke and you are not. Assume your mechanics have checked all the easy stuff like checking the hoses, checking the turbo bearing, throttle, etc. Were it mine, I would hook up a temporary boost gauge and see what it says. Good luck.
View attachment 93209

We tested drilled out one of the plugs and attached a boost gauge and we had plenty of boost. I suspect the reassembly of the turbo screwed things up. We will check it our. Thanks again.