Need Board Wisdom...Diesel Engine issue has me stumped

[Chris Reinke]

Need Board Wisdom...Diesel Engine issue has me stumped

Owning a boat is always an experience. I am having an issue with my diesel engine and I am totally stumped. I apologize for the lengthy listing of facts but I know the folks on this board like to get all the facts to help troubleshoot a problem.

Here are the symptoms:
- I am motoring at 2000 RPM’s and the engine will suddenly drop to 1500 RPM’s without anyone touching the throttle, and moving the throttle further forward has no effect on increasing RPM’s. This situation will either last for a few minutes and then RPM’s will increase back to 2000, or the engine will remain at a max of 1500 until it is shut down and restarted.

Some History:
- I had the engine rebuilt by Hansen Marine before last season (rebuild did not include replacement of fuel pump)

- At the time of rebuild I had the fuel tank drained and cleaned.

- I had a similar problem earlier this summer and I replaced all 3 fuel filters thinking it was a partial clog:
o Bulkhead mounted primary filter/separator
o Engine mounted canister filter
o Fuel pump mounted screen

- After replacing all the filters I had the same problem occur a few days later (big frustration!). The very helpful guys up at Hansen Marine (they did the rebuild) advised that it may be a fuel pump issue so I replaced it.

Recent occurrence:
- This over the past 2days I sailed / motored from Cape Cod, around NY and up the Hudson River. Due to lack if wind….and I tight work schedule…I ran the motor pretty much non-stop the entire 37 hours. The engine worked perfectly and was humming at 2,000 RPM’s from when I left Cape Cod at 7:00am Sunday morning until I pulled in to Huntington Harbor, Long Island to refuel around 9:00am Monday morning. It then ran perfectly from Huntington Harbor, through Hell’s Gate (thank God), around NYC and up the Hudson until 7:30pm Monday night. I was only 2 miles from my home port and the RPM’s dropped!!!!

Any ideas or thoughts on how to trouble shoot would be appreciated. My fuel pump appears to be functioning (I hear the clicking). My fuel lines appear to be flowing (I get fuel out the injectors).

HELP!

[Parfait's Provider]

Chris,

I probably won't be any help anyway, but what engine do you have?

[Oswego John]

Chris,

My first thought is fuel, or lack of it.

Have you had the fuel pump pressure tested to see if it can supply surplus fuel, or is it just above borderline?

Have you checked the bypass return fuel line?

Just a long shot, but check for an intermittent air leak or crack in the hose or connections feeding into the fuel pump.

Good luck,
O J

[Parfait's Provider]

Is it possible the fuel line is collapsing? Seems like it has to be something like that if the problem goes away when you shut her down and restart. Filters don't clean themselves, pickups either; pumps don't suddenly get better if they rest for a few seconds.

[Chris Reinke]

The engine is a Westerbeke M-30.

John - Thanks for the ideas. I had though of the hoses, but they were all just replaced last season as part of the rebuild. I checked all theconnections when I replaced the filters and the fuel pump.

I was in some chop during the overnight on Monday (2-4) and it ran fine, I was in calm water on Sunday morning, and it ran fine. It was glass calm on Monday night when the RPM's dropped.

[Dean Abramson]

I am wondering if this latest incident is unrelated to the others. Did it drop to 1500 again?

I have had instances when something caught on the prop caused a reduction in revs. Once it was a bunch of kelp, another time it was a piece of a plastic bag.

Now, if I even think I have had a slight dip in revs, I will reverse the engine, go forward, reverse again, etc. Sometimes you can spin stuff off that way.

Dean

[Boyd]

After a spate of engine and fuel filter problems I installed a vacuum gauge on a tee ahead of the lift pump. That way if there is an obstruction or clogged primary the gauge will show it. Its a good indicator when routine filter changes are needed if nothing else.

A sticking valve can cause an rpm drop. My dad had a car that would have intermittent power loss events and that was the cause.

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

[seadawg]

Does that engine have a speed govenor? just a thought to add to the pile.

[Ben Thomas]

checking the fuel system with a vacuum gauge is an excellent idea.

Have you checked the air intake/ filter for any obstruction that may cause the intermittent problem? Starving the engine of air may seem like a fuel problem..since they go hand in hand. Just a thought Good luck, Ben

[Steve Kuhar]

Just another thought for what it is worth. It seems that the problem you describe could be caused by a blocked fuel tank air vent. It would be easy enough to verify this by cracking the fuel fill cap while the problem is occuring, if the engine regains RPM that is it, and if not it didn't cost anything to try. Let us know what you eventually find out.

Steve Kuhar

[Matt Cawthorne]

If you have extra crew to drive the boat then try this. When the engine speed drops to 1500 rpm loosen the fuel line to one of the injectors. If the engine speed drops then tighten it up again and move on to the next injector. If you find one for which the engine speed does not drop then you have identified an injector or part of the injection pump or fuel line that is faulty. Be very careful around all of the moving parts. Wear appropriate safety goggles and perhaps some rubber gloves. It really sounds like some sort of fuel starvation or a lifter or valve that is sticking. I feel for you. The intermittent problems are always the worst to deal with.

Good luck.

Matt

[Ron Brassord]

If you temorarily install a short piece of clear tubing after the fuel pump and before the injector pump, you can determine if there is a an air leak anywhere in the system. "Tiny bubbles" is not just a song?
I changed out everything in my diesel fuel system, and thought nothing could be wrong with it. It turned out one fitting was overtightened and leaking air intermittingly. I always carry the clear hose as a sure test for fuel problems.
Just a thought
Good luck Ron B

[Chris Reinke]

Thanks all for some great ideas on where to try and troubleshoot the problem.

I really like Ron's idea of a clear hose to identify air leaks, and Matt's suggestion of loosening an injector fuel line to isolate if it is an injector issue.

I am also very interested in Boyd's recommendation of a vacuum gauge. It sounds like a great thing to have for general maintenance as well. I was hoping he could elaborate. What is the normal vacuum pressure that the filters create when in good working order? I know my fuel pump is rated at 4-7psi, but I have no clue what resistance the primary and secondary fuel filters would create. Is it a standard part that most auto part stores can supply?

I will be back on the boat this weekend to try some of these suggestions.

Thanks

[Boyd]

Hi Chris:

Racor sells one as a standard accessory and its the one I used. It can be mounted on the filter itself or seperately in a more convienent panel with an extension hose. I made a little starboard panel that mounts in the line locker where I sit at the helm, so all I do is lift the lid to see it. I suspect any vacuum gauge that reads acurately in the range of .5 to 10 psi would work.

A new filter reads virtually zero or so little that its barely perceptable. I was told by Westerbeke that the engine will shut down completely at -7psi. I start having problems when it reads
-4psi or so. Usually the engine will not reach full governered no load rpms at that reading... time to change the filter. I watch and if there is any appreciable increase in reading at all then I know the filter is about due.

If you have a significant restriction in the system such as an intermittantly collapsing fuel line then it would show up immediately.

This gauge only measures the suction before the lift pump. A clogged lift pump filter would not be detected by this gauge. Usually I replace the two filters at the same time.

This and Ron's transparent hose should diagnose whatever ails it.

Let me know if you need more information.

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

[Neil Kozlowski]

Chris,

You mentioned you had your fuel tank cleaned. This is what was done on a CD32 and years later, the same symptom you have occurred. The problem was a little scrap of paper toweling that was lodged in the right angle tank fitting at the top of the pick-up tube. When this tiny scrap was removed, the problem went away. A way to verify you do or do not have this problem is simply install a bulb ( the type used in a typical outboard application ) in the suction line BEFORE your first filter. If the bulb collapses, when the rpm reduces, you have a restriction in the pick-up line. It is also a simple matter to remove the fitting and check to see if the pick-up tube and right angle fitting are clear. The piece of paper removed in the CD 32 was no bigger than a dime, but at times it completely stalled the engine. After the owner waited about 10 minute ( enough time for the pressure to equalize) the engine would restart and run for a few minutes or quite a while depending on how the paper rejammed in the fitting.

Good luck in your quest.