New Cummins QSB 6.7 liter with problems

[Doug Snider]

At the end of February we took possession of a new 2023 Helmsman Trawlers 38E Pilothouse trawler with a Cummins QSB 6.7 liter 250hp diesel engine. Several problems have occurred with the engine, beginning during delivery from the transport ship to the dealership and continuing through 53 hours of engine operation.

Problem 1: Engine starts normally and shuts down after running for a few seconds. The engine restarts normally and runs without incident. This happened when the boat was being delivered and frequently during commissioning with less than thirty engine hours. This last occurrence was at 46 engine hours.

Problem 2: Shortly after getting underway, a low fuel pressure alarm shows on the engine panel and the engine shuts down. This has happened three times, at 22 hours, 47 hours and 50 hours.  When the alarm occurred at 47 hours, the engine continued to run at low RPM for about thirty seconds with no throttle response and then shut down. On all three occasions, the engine was restarted and operated normally.

Problem 3: On several occasions, there have been momentary RPM drops while cruising at a steady RPM.

Problem 4: Going through a heavy current, the engine hesitated (RPM drop before increasing) when the throttle was advanced to compensate for the current.

We don’t know for sure that the problems are related. We have made several trips with no occurrence of these problems. Cummins technicians have been on the boat twice. On the first visit, they tightened the injectors. On the second visit they replaced the lower helm electronic engine control which was under a recall program.

Does anyone have any suggestions for a possible cause?

Topic

[Doug Snider]

It appears our engine issue has been resolved. Cummins replaced the lift pump, the low pressure pump and the on engine filter. Everything performed nominally on a sea trial following the repairs. It appears that the low pressure pump was out of tolerance and only delivering 30 psi when it should have been around 70 psi. We took the boat out on a 35 mile cruise, cruising at different RPM. The engine started normally and ran continuously with no RPM fluctuations and normal throttle response. 

Thanks for pointing Cummins in the right direction. Helmsman Trawlers escalated the problem to the regional level with Cummins and the service call happened very quickly. 

[Doug Snider]

Thanks Tony

With your input, we now have two  Cummins offices and two service managers aware on the problem(s) with a very comprehensive list of possible faults and things to investigate. They are on notice that if the issue is not resolved to our satisfaction, we will be relying on your services to get our boat finally operational. 

[Tony Athens]

Did the “tech” perform  the most obvous tests based on the symptoms??

 

  Put a 0-100 PSI analog gauge on the on-engine last chance fuel filter to “see” if you were having fuel supply issues? I believe pressures there are in the 80-90 PSI range when running on a 6.7    

 

Did he 100% assure the that the one-way fuel check valve next to the electric fuel pump down by the ECM was not installed backwards– We have now seen two of these with symptoms very similar to yours. Pics of this on this web site.  

https://www.sbmar.com/articles/qsb-6-7-fuel-hook-ups-and-fuel-direction/    

 

Did he put a analog vacuum gauge between the engine and the fuel tank and monitor it while running?    

 

Did he cut open the on-engine fuel filter and dump it into a clean glass container to “see” what is getting to it ( past your off-engine primany filters system?      

 

ECM alarms / codes are great  but do not always pin-point issues like you are describing ?  But it certainly adds up to the warranty or repair claim $$

[Clark Leighs]

I may annoy you but go back to Tony’s reply and info request.     Do as he asks, all of it, as he asks. He may download some of it to study but  sometimes these cute movies are not as helpfull as the posters believe.  

 

Of course add what you wish but do what he asks.

 

 

Has your mechanic checked fuel pressure and line vacuum?

[Doug Snider]

Today a Cummins field technician worked on the boat for five hours. He replaced the fuel actuator before we did a sea trial. The engine started normally without incident. When we throttled up underway, at a little over 2,000 RPM, the fuel pressure would drop abruptly and I had to throttle back to idle to keep the engine from quitting. Upon returning to dock, the technician ran a series of diagnostic tests. He had several theories including a bad pressure relief valve and metal shavings in the fuel system. <br />After a phone call, he said he had ordered a new fuel pump. It seems like there still isn’t a definitive answer to what is causing the problem. 

[Doug Snider]

I took a video of the start and stop event today. The video is too large to upload. Here’s a link to the file on my Synology disk station server. http://PatAndDoug.quickconnect.to/mo/sharing/wjrA4f05k

It shows the engine display from startup to the engine shutting itself down. 

[Doug Snider]

Thanks Tony,

  We have the Cummins tech coming back tomorrow so your suggestions are very timely. I’ll get some photos of the instrument panel, engine and the other data you requested tomorrow. In the meantime, here’s a current photo from the engine room security camera. <br /><br />

  We did several test starts today and the immediate shutdown after start reoccurred. I have a video of the event. The low fuel pressure alarm events have all been underway, a few minutes after departing.

Thanks,

Doug

[Tony Athens]

#1—————–What exact digital insturmetation to you have ?    Got a good picture of you helm station with your intruments turned on?  

#2–If you have had Cummins techs on the vessel, did they give a you a printout of the alarn exact codes that would have shown up on their computer? This is super important, especailly if they have not/did not fix the glitch.

#3—– When the engine does run “normally” , write down GPH  and vessel speed at 1200 RPM, 1600 RPM, 2000 RPM, 2400 RPM and at WOT RPM ( what ever that is) 

4) Send me good pictures of the engine as installed in the vessl  from all perspectives……………………….. I want to “see” the installation as if I was on the vessel looking it over    

[Author]

Replies