Diesel intermittent Low RPM stall

[Monterey385]

My 3 cylinder diesel has begun to intermittently stall immediately after starting about 10% - 20% of the time. It tends to start on the next try. Have not had any performance issues.

It’s 4 years old with 450 hours ... ran perfectly until this season when this started about mid - season.

Any thoughts?

 

[JohnShannon]

In neutral? Is this when it goes into gear

 

[SycloneDriver]

We are going to need a little more detail.
First cold start of the day?
Starting procedure please?
How does it run?

 

[Michael Davis]

Have you recently changed fuel filters?

 

[senang]

Nearly new engine that was running without problems, my bet is that it is fuel related. Air in the lines, crappy fuel, blocked pickup tube, ....

 

[NYSail]

Clean your injectors to start....

 

[jssailem]

Clean your injectors to start....

NYSail. Wouldn't it be easier to clean the fuel filter, the pick up tube, check that the fuel and tank are clear and assure that the fuel lines were air tight, then to remove the injectors and subject them to cleaning?

 

[dLj]

When did you last change the fuel filter? How many tanks of fuel have you gone through? Does diesel remain in the tank for extended time? Are you using a biocide in your fuel?

Enough questions for now - more may come after these are answered.

dj

 

[NYSail]

NYSail. Wouldn't it be easier to clean the fuel filter, the pick up tube, check that the fuel and tank are clear and assure that the fuel lines were air tight, then to remove the injectors and subject them to cleaning?

He said he has no performance issues and that only issue is starting every now and then. Led me to believe that after started no issues. If it were air in line my experience has been it would continually cause issues. And also a filter issue would be a continual issue. Now if the injectors were getting a bit cruded up, there could be an issue starting and once debris was “digested” it would be fine. Pouring a bottle of sea foam in your primary filter does wonders to clean the injectors..... but yes without a doubt all other items need to be checked as well.

Im no mechanic...... just have been keeping my boat running starting with the simplest thing for 20 years.

Greg

 

[Stu Jackson]

Is there a reason to not tell us what engine it is?

 

[Benny17441]

90% of engine maladies are fuel related. Bad fuel, dirty fuel tank, clogged filters, air in the fuel lines.....

 

[Monterey385]

In neutral? Is this when it goes into gear

In Neutral

 

[Monterey385]

We are going to need a little more detail.
First cold start of the day?
Starting procedure please?
How does it run?

Typically doesn't happen on first cold start of the day
Starting procedure is simple ... ignition key engaged, wait 1-2 seconds, press start button, hit neutral button on throttle, and if necessary throttle up to engage alternator and any other rpm based items, return quickly to neutral. When intermittent stall occurs, it tends to occur whether I apply the throttle in neutral or not. Typically after 1-2 more tries, engine starts and runs.

Once engine starts and runs, it seems to be operating within normal limits and or routinely.

 

[Monterey385]

Have you recently changed fuel filters?

No change in filters since beginning of season but filters are changed every year when winterizing.

The only thing I can think of along these lines is about a month - 6 weeks ago, I did run out of fuel while underway. Once refueled from an portable diesel container, engine restarted and ran fine.

I cannot recall for certain whether the intermittent issues started before or after the running out of fuel.

 

[Monterey385]

When did you last change the fuel filter? How many tanks of fuel have you gone through? Does diesel remain in the tank for extended time? Are you using a biocide in your fuel?

Enough questions for now - more may come after these are answered.

dj

See previous answer on fuel filter. I carry 40 gallons so I am still working the same tank since it started. I tend to use about 2-4 tanks of fuel a season depending on travel. I do use biocide.

 

[Monterey385]

He said he has no performance issues and that only issue is starting every now and then. Led me to believe that after started no issues. If it were air in line my experience has been it would continually cause issues. And also a filter issue would be a continual issue. Now if the injectors were getting a bit cruded up, there could be an issue starting and once debris was “digested” it would be fine. Pouring a bottle of sea foam in your primary filter does wonders to clean the injectors..... but yes without a doubt all other items need to be checked as well.

Im no mechanic...... just have been keeping my boat running starting with the simplest thing for 20 years.

Greg

This is all correct. I use Seafoam religiously with my dinghy outboard with great results.

NY Sail, would you confirm that when you use Seafoam to clean injectors you use it via the Racor and you pour an entire bottle (16 oz) directly into the Racor and not into the main diesel tank?

 

[Monterey385]

Is there a reason to not tell us what engine it is?

Nope, apologies, its a 2016 Yanmar 40 hp 3 cylinder on a 2016 Catalina 385. I'm blanking on the actual Yanmar product number.

 

[Monterey385]

90% of engine maladies are fuel related. Bad fuel, dirty fuel tank, clogged filters, air in the fuel lines.....

Understood, the part of this that was perplexing was the intermittent nature of the issue followed by the engine running properly. Racking my brain, I could not figure out this fact pattern.

Let me add one item to the fact pattern that a colleague noted that the engine appeared to vibrate a little bit more than normal when idling. Understanding diesels are very different from gasoline engines, but the gasoline analogue would be a slightly out of tune carburetor idle setting leading the engine to run roughly and intermittently have trouble starting.

I can't think of any set of situations in a diesel that would replicate these issues with no carburetor.

 

[dLj]

Well, you've sure got a head scratcher.... But it's sounding more and more like injectors. Running out of fuel isn't good for the injector pump in some diesels by the way. I don't know if that applies to yours. The fuel is a lubricant. Running out of fuel means running low on lubricant. But the intermittent description doesn't sound like the pump here...

I'm still holding onto changing your fuel filter. Easy/fast to do and you might have picked up stuff when you ran out of fuel. Next (or at the same time), I'd try NY Sails suggestion to try a cleaning fluid to see if that helps.

I've got nothing else for you...

dj

 

[Monterey385]

Well, you've sure got a head scratcher.... But it's sounding more and more like injectors. Running out of fuel isn't good for the injector pump in some diesels by the way. I don't know if that applies to yours. The fuel is a lubricant. Running out of fuel means running low on lubricant. But the intermittent description doesn't sound like the pump here...

I'm still holding onto changing your fuel filter. Easy/fast to do and you might have picked up stuff when you ran out of fuel. Next (or at the same time), I'd try NY Sails suggestion to try a cleaning fluid to see if that helps.

I've got nothing else for you...

dj

Thank you, I appreciate it.

Quick question for the group ... if there happened to be a slight bit of air in the system from when i ran out of fuel and re-filled, would that create the intermittent symptoms? My engine self-primes and I've never actually bled the line the way I had to on other diesels I've had. I was always told that once the engine starts, it will self-flush any remaining air ... but I started to get curious.