Yanmar 3GM35F Intermittent Out-of-Control Revving

[DotDun]

Originally Posted by unbusted67

About how much did that cost? And I am sorry the model in question is a 3HM35F not a 3GM, sorry about the discrepancy.

IP rebuild and (3) injectors was ~$250. I pulled them off the engine and took them to the shop. The critical piece is calibrating the IP so that all cylinders are getter the same amount of fuel. The IP has one fixed pump and (2) adjustable ones. Hence the shop needs to mount the IP on a machine, run it, and make sure all three pumps are putting out the same amount of fuel.

If you remove/install the IP yourself, be very careful the get the govenor arm back on the IP rack. If you mess this up, the engine will run away with itself as soon as you start it. The ONLY control on this engine is the rack on the IP, no other way to shut it down. There is an inspection plate where you verify that everything is lined up, check it 2 or 3 times!

I don't know about the 3HM35F, so I wouldn't be able to help.

[unbusted67]

Ok Thanks.

[Tellie]

1700 rpms? Like NM said, read the manual.

[unbusted67]

Originally Posted by Tellie

1700 rpms? Like NM said, read the manual.

And like I said we are trying to save fuel. The fact that the engine doesn't mind being run a higher RPMs does not negate the fact that it is revving without us pushing the throttle, which to me is problematic because it is running differently than it would be normally. We are in Baja, far away from a diesel mechanic or even a gas station.

[never monday]

Originally Posted by unbusted67

And like I said we are trying to save fuel. The fact that the engine doesn't mind being run a higher RPMs does not negate the fact that it is revving without us pushing the throttle, which to me is problematic because it is running differently than it would be normally. We are in Baja, far away from a diesel mechanic or even a gas station.

and I'll say it a little slower this time
if your not operating the engine properly.

how do you know it's broken

[unbusted67]

Originally Posted by never monday

and I'll say it a little slower this time
if your not operating the engine properly.

how do you know it's broken

NM if you don't have anything useful to say please just stay off this thread. You are taking a very armchair approach to this whole thing.

When in the harbor and day sailing we will normally run the engine around 2400 rpm since we are away fuel pumps and trying to conserve we are running the engine a little slower. There is nothing in the user manual that says don't run your engine at lower rpms. Every time we try to push the engine above 2000 rpm it runs away. In the same way that if you were on the highway and your car was giving you trouble you wouldn't put the petal to the floor and get in the fast lane, you would pull off the highway and take it easy We are on a lonely coast with limited ports and anchorages so we are trying not to make the problem worse by repeating the incident. Or do I need to say that a little slower?

[never monday]

Originally Posted by unbusted67

Every time we try to push the engine above 2000 rpm it runs away.

since when did 2000 RPM become a "run away" diesel with a Yanmar 3HM or 3GM.


you have what you perceive to be a problem, that may very well not be a problem. And you refuse to take the measure to properly document or diagnose the perceived problem.


good luck in your endeavors. I'm done wasting my time on you

[Gnitfar]

For what it's worth, I had a very similar situation with my engine revving periodically, but it was with a Perkins 4108, not a Yanmar. After weeks trying to find the issue, it turned out to be a failed aluminum crush washer at the fuel-supply/fuel-return banjo fitting atop the secondary fuel filter. A small amount of air was finding it's way into the fuel supply going to the IP that caused the revving.

[delmarrey]

unbusted67,

Did you ever check your motor oil level???

[susan kennedy]

Why so rude Never Monday?

[Roy M]

Why hasn't anyone mentioned an air leak in the fuel line. If I was careful reading, I thought unbusted67 said that the rpms increased suddenly, and they shut the engine down (before it, maybe, would have conked out from lack of fuel). Perhaps a simple bleed check for air in the injector lines, followed by general tightening of the connectors all along the fuel pickup circuit might offer some leads. OOps, Gnitfar did mention that possibility. Sorry!

[Laidback]

Don't believe any rudeness was intended - when members ask for help in trying to diagnose a marine engine problem, surely it is incumbent upon that member to supply as much accurate information regarding the problem and the engine model?
For clarification here is the rating Specification for Continuous Operation and Peak RPM (1 hour) for that engine :-

3HM35F Continuous Duty Rating = 3200 RPM (30 HP)
3HM35F Peak (One-Hour) Rating = 3400 RPM (34 HP)

Diesels run at an RPM well below specification for very long periods, have the potential to 'glaze' the cylinder walls. What is recommended to prevent glazing, is every hour or so, to run the engine for say 10 mins at its Continuous Duty Rating RPM.

[unbusted67]

Originally Posted by never monday

since when did 2000 RPM become a "run away" diesel with a Yanmar 3HM or 3GM.

No, 2000 rpms isn't the run away speed, it is the speed at which the engine starts to run away. I am estimating that the engine gets up to about 24-3200rpms before we shut it down.

Originally Posted by delmarrey

unbusted67,

Did you ever check your motor oil level???

Yes, and sorry for not getting back to you about that. The engine oil level was at nominal as was the transmission oil.

Originally Posted by Roy M

Why hasn't anyone mentioned an air leak in the fuel line. If I was careful reading, I thought unbusted67 said that the rpms increased suddenly, and they shut the engine down (before it, maybe, would have conked out from lack of fuel). Perhaps a simple bleed check for air in the injector lines, followed by general tightening of the connectors all along the fuel pickup circuit might offer some leads. OOps, Gnitfar did mention that possibility. Sorry!

I thought that too but the second time it happened we just throttled way back and took the engine out of gear and let it idle. It didn't die.

Originally Posted by Laidback

3HM35F Continuous Duty Rating = 3200 RPM (30 HP)
3HM35F Peak (One-Hour) Rating = 3400 RPM (34 HP)

Diesels run at an RPM well below specification for very long periods, have the potential to 'glaze' the cylinder walls. What is recommended to prevent glazing, is every hour or so, to run the engine for say 10 mins at its Continuous Duty Rating RPM.

It was my interpretation of those specs (rpm vs hp) that they are simply saying: if you want the predesignated HP of this engine (34HP) run it at 3400 rpm. Not that you have to for the well being of the engine.

I am aware of the glazing problem and pretty conscious of it in my use of the engine. There are times at anchor when we run the motor at low rpms but I do usually try and give it a good work out once a week or so. Is this a symptom of glazing? Could it be that on this trip we have been running the engine at slighty lower rpms and it has caused glazing?

[Laidback]

If the engine is run at the continuous rating of 3,200 RPM for 10 minutes for every 60 mins running at low RPM it will do the engine some good.

Now returning to the symptoms described briefly :- these are indicative of a leak in the fuel delivery system.
Take for example : what happens for a very brief period when a diesel engine starts to run out of fuel :- the RPM if running say at 2,000 will suddenly receive a mixture of fuel + air = increased combustion = speeds up = equals increased suction = more RPM until there is no more fuel.

Now, if there there is a minor leak somewhere in the pipework or connections - then at low RPM a trickle of small air bubbles may be sucked in to join the fuel on its way to the cylinders = no problem.
Increase throttle for more RPM = more bigger bubbles of air = increased combustion = more RPM without change in throttle movement. Engine appears to rev-up out of control.

Gnitfar and RoyM have already suggested that you check your fuel delivery system for leaks - even if you do not find any - go round every connection and tighten them up. Once you have completed that task - Test the engine by starting it - run it at around 1800 RPM, until it is warmed up, progressively increase the RPM in stages of 400 RPM until it is running at 3,200 RPM. Check the fuel system for leaks, Check the exhaust for smoke and water. Record results and log them.

[never monday]

Originally Posted by unbusted67

No, 2000 rpms isn't the run away speed, it is the speed at which the engine starts to run away. I am estimating that the engine gets up to about 24-3200rpms before we shut it down.

without documentation of the engine exceeding 3700-3800 RPM. It is NOT a runaway. Please establish the top RPM achieved in and out of gear.