6bta 5.9 CPL 970 won't exceed 1800 rpm

[Dave Weber]

Hi Guys,

New to forum and need some help.

I’m hoping you can help me out with a problem I am experiencing with my boat engine, Cummins 6BTA 12 valve 5.9 M2 EP-9 injection pump. The problem I’m having is with the port engine which fires up without hesitation and runs great up to about 1800 rpm at this point I can continue advancing the throttle but there is zero response, this all happens under load. In the neutral position the engine functions normally and will rev up to 3000 rpm. The starboard engine performs normally and both are 1992 vintage with approximately 1250 hours on each. Has proper after coolers.

I acquired this boat in August of 2018 and the engine problem was present at that time so I am unable to give you any operational history. Here is the details of the engine:

ESN: 44724555

MARKETING MODEL NAME: B5.9M (300)

BUILD DATE: 02 MAR 1992

FUEL PUMP PART# 3919762

MARKETING ENGINE CONFIG. :D403017MM12

TECHNICAL ENGINE CONFIG. :D403017MX02

CPL# 970

300 HP @ 2800 RPM

The following has been done in troubleshooting this problem:

Primary fuel filter cleaned and element replaced

Engine fuel filter replaced

Pressure check of port lift pump taken after filter and before PE-9, 15 psi idle to 20 psi @ 2400

Pressure check of starboard engine produced identical results and it runs great.

1000 rpm under load at dock 15 psi both engines individually tested.

Over flow/return valve removed and cleaned, ball and spring seemed ok. Air bled from pump

Throttle linkage and function checked along with throttle stops, both stations normal (boat equipped with ZF Micro-Commander controls with synchronization)

12 volt trombetta shutoff valve removed and serviced per sbmarine how-to.

Shutoff arm checked and springs to run position when solenoid is retracted

Aneroid tube to intake manifold removed and checked

I was able to read the governor number on the starboard engine which showed Nippon Denso 190300-2950, I was not able to read the port do to position of the plate. (I am able to get it but will require substantial effort and it’s the same governor).

Engine is one of two in a 1993 Bluewater Costal Cruiser 5400 (BTTL54237J293) Trans TRM25A #225-625L Prop Federal EQVI Quad 24 dia. 26 pitch Heavy Cupped 1.5 bore.

Thanks in advance for your help. (I would bring the boat to sbmarine but a long trip from Ohio River mile 498!)

Dave

Topic

[Angel I Collazo Martinez]

Was the issue ever solved? Was the aftercooler the problem or the aneroid?

[Dave Weber]

Rpm up to 2300

Realizing from the previous tests that fuel delivery was not the problem but rather a restriction of air/boost to mix with the fuel. The servicing of the aftercooler no doubt helped with air flow but I decided to change the intake filter and try a less restrictive high flow performance filter. The results were positive, boost went from 5 psi to 15 and rpm increased to 2300. A big improvement but still not the 2800 that the starboard engine produces.

I will continue on with leak tests to ensure I am getting all the boost I can and the system is leak free. Can someone please tell me know what kind of boost numbers I should be obtaining for this M2 engine with the H1E turbo?

Tony, thank you for your excellent guidance as I worked through the troubleshooting process, Any suggestions on the turbo, boost, and increasing rpm to specifications is appreciated.

[Dave Weber]

The parameters had changed, there was black smoke because I was forcing the system to think that it was getting higher boost, moving the aneroid diaphragm down allowing more fuel but not air causing a fuel air imbalance. Read some of the threads before and you can follow what we were trying to do.

[Rob Schepis]

Dave Weber wrote:

……..The minute I throttled back below 1600 the black smoke disappeared in all cases….

Black Smoke ??? …….This thread started with “No Black or Dark Smoke” ??

[Dave Weber]

Fake boost test results

Tested aneroid at 20, 25, 30, and 35 psi. All pressures produced the same results of black smoke at 1600 rpm and no further throttle response after 1600-1800 rpm. Boost was measured from the existing aneroid line while the tester was hooked up and only measured 2-5 psi.

The minute I throttled back below 1600 the black smoke disappeared in all cases.

Everything was leak tested prior to performing the aneroid test to ensure accurate results.

[Tony Athens]

Tap thru the double wall where the cap it and install a 0-60 PSI gauge.. I want to “see” the pressure on the aneroid diaphram.

Tony

[Dave Weber]

Fake boost for aneroid

Hi All,

Sea trial result a little better, 2000 rpm, but I’m not so sure it wasn’t the starboard engine dragging up the port. Static boost at 2000 was 5 psi.

I’m going to do a “fake boost” test next. I have built the device pictured below so that I can pressurize the aneroid to simulate 20-30 psi boost and maybe I can loosen up the diaphragm if it is stuck. Also, I will be doing a boost leak test and have to build the device to test it. Stay tuned for further results.

[Dave Weber]

Tony, I have the equipment to set up the “fake boost” and will hook it up if my test run today is unsuccessful in producing higher rpms. I plan to go right into the aneroid connection with a regulated psi of 20 lbs static.

Thanks again,

[Tony Athens]

2000 RPM in neutral = no engine load= very little fuel asked for=no HP produced=very low exhaust flow=NO BOOST.. Boost is a function of exhaust flow ( about 500 CFM per 100 HP produced / 5-6 GPH of fuel burn)

Report your findings————————————- Are you set up to “fake boost” and feed the aneroid with 15-30 PSI of air pressure in case it ( aneroid) is stuck or extra LAZY? That’s called a “just in case”, as if you do not see what we are trying to sort out, that is next…

BTW, your aftercoolers needed servicing, BIG TIME..Glad you went for it.

Tony

[Dave Weber]

Hi Dan,

The cause was never sorted out. I have done everything Tony has advised me to do and just completed reinstalling everything yesterday. I paid special attention to the couplings and tubes to make sure I didn’t have any leaks and everything was sealed up good.

I’m new to the whole diesel boost and aneroid thing so I’m not real sure when and how much boost I should be reading and under what conditions? I didn’t have any in neutral at the dock when I revved it up to 2000 but then I didn’t really expect any without a load. (any guidance in this area would be appreciated)

I plan to take the boat out tomorrow to see if it will now get over 1800 and run like it should, I have gone over everything from the turbo to the intake manifold (turbo spins freely and smooth and does not move in or out or side to side when operated by hand). I will post results after my trial cruise.

[Daniel Brahniuk]

Was the cause ever sorted out on only getting 1800 rmp no boost?

[Dave Weber]

Aftercooler reassembly – photos

Cleaned, greased up and reassembled. Ready to go back on port engine after installation of anodes.

[Dave Weber]

Photos of port aftercooler

Tony,

Here’s the photos, didn’t look too bad except for the impeller parts the previous owner left for me! This is off the engine I am having a problem with and it came apart real easy so it must have been lubed up when serviced before, all removed by hand.

[Dave Weber]

I’m taking it off today and bringing it home for disassembly. I will get pictures and post.

[Tony Athens]

Dave,

Back to basics–NO BOOST=NO FUEL=NO HP=NO RPM..

Get them off and get them into pieces on the bench.. I want pictures before and after..

Tony

[Rob Schepis]

Nil boost could be a leaking air hose/tube, busted clamp, etc., check it all carefully.

[Dave Weber]

Boost test

I just got a boost gauge hooked up on the troublesome engine and found under load at 1800 rpm only one pound of boost! Removal of aftercooler and disassembly is next. Please comment if any of you have had similar problems.

Thanks

[Dave Weber]

Forgot to mention that this was not an all of a sudden occurrence. The low power/rpm problem was present when I got the boat 1 year ago.

[Dave Weber]

Tony,

I trust your guidance and appreciate the help and of course I will service both aftercoolers, they were on my agenda for this winter when I’m not using the boat but I think I will at least get the port done sooner. Your last post made a lot of sense and the aneroid pressure effect on fuel volume. Do the diaphragms in the aneroid ever need replacement?

Thanks again for your help

[Tony Athens]

Dave,

Your aftercoolers need to serviced——————PERIOD.

I am also 72, so that excuse does not fly with me.. What I can no longer do, or want to do, I mange a young buck to do. That what old guys like us do.

Realize, you have an “aneroid” on your ND PUMPS………………….. No or low boost = NO FUEL or minimum fuel= No power when the engine is loaded = NO RPM when loaded & also equals NO DARK SMOKE..

You have to do what the symptoms point to. If I am wrong, at least now you know what you have as to internal aftercooler condition .

If you are dead set at testing and not servicing, then do it this way———- figure out a way to put a steady 20-30 PSI on the line going to the aneroid and go for a ride. IE, fake the boost by opening the aneroid to give the engine fuel.

BTW, was this an “all on a sudden” occurrence?

Tony

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