Throttle lag on Hylas 54 Yanmar 4JH3-DTE

[tulsag]

Has anyone experienced 'throttle lag? My Hylas 54 with a Yanmar 4JH3-DTE is suffering from this increasingly.

We are having a strange throttling up problem. It used to only happen occasionally when switching into reverse but now it is starting to happen when engaging into forward. When I push the throttle into gear, sometimes the RPM’s have a significant lag ( 1 to 10 seconds) before they start to suddenly climb to the appropriate rpm’s in a rush. This is getting worse and happening more often. I have changed the filters and I can hear the gear engage when I leave neutral/idle but the lagged response is really strange.

All of the throttle/gear linkages appear to be moving appropriately. Strangely, it does not lag when I push the button in and attempt in neutral. A friend suggested it may be the fuel injection pump that needs to be rebuilt since Yanmar does not make this engine anymore.

Note: I had new injectors put in this winter. But it started doing it last summer a couple of times. It has continued, and slowly gotten worse, after the new injector tips were put in.

Any thoughts? This is really scary!

Mark Powell
s/v TARA
Croatia

[DougR]

If you are sure the transmission is actually engaging and not slipping, I would check the turbocharger and exhaust system for soot and carbon buildup.

DougR

[tulsag]

No, the engine acts like it is not even trying to throttle up. If it was the transmission, the engine would be revving like crazy prior to accelerating. It acts like it is a cable problem but it is not because the movement it identical when it throttles up and when it doesn't respond.

I friend suggested that re-building the injection pump stops an internal 'sleeve' from sticking. That is the only thing that makes sense.

Mark

[Kenomac]

Originally Posted by DougR

I would check the turbocharger and exhaust system for soot and carbon buildup.

DougR

This is what I was going to write.

[SV Bacchus]

My first thought was linkage until you said it had been checked. My next thought was turbo or exhaust.

You then state "Strangely, it does not lag when I push the button in and attempt in neutral." So now I fall back to linkage but thinking instead of cables start looking at your shifter.

[Dockhead]

First thing to check is fuel.

Then, the second thing is -- fuel.

The third thing to check is -- fuel again.

Only after that, start thinking about anything else. 97% of problems like this are caused by fuel (and 98.6% of statistics are just made up ).

Change the fine filter and try to run the engine from a jerry can of clean fuel, bypassing the primary filter/water separator and all the fuel lines up to the fine filter on the engine.

Check the injection pipes and injector connections for cracks or leaks.

Obviously, bleed the whole thing, but note that the 4J's are theoretically fully self-bleeding, so very unlikely to have any effect.

If the symptoms remain after every possible fuel problem has been eliminated, then check the exhaust elbow for carbon, and have a look at the turbo vanes, feel the turbo for smooth bearings. Have you ever done the turbo wash in the maintenance schedule? I have never heard of a Yanmar 4J with any problem caused by carbon in the elbow or dirty turbo impeller, but you should be careful to follow the mechanic's golden rule -- ALWAYS check the easiest stuff first, working your way slowly and systematically up to the more complex stuff. The injection pump should be the last thing on your list, and by the way, it is extremely rare for them to create this kind of problem.

If you do get as far as the injection pump, then you just take it off and take it to an authorized service station to be bench tested. After the bench test, you will know everything about the injection pump, and the lift pump which is built into it, eliminating all of that as a possible source of the problem. Albeit expensively, as the bench test costs a couple hundred, and taking off and putting back on and properly adjusting the pump is a PITA which might require professional help.

[Dockhead]

Originally Posted by SV Bacchus

You then state "Strangely, it does not lag when I push the button in and attempt in neutral." So now I fall back to linkage but thinking instead of cables start looking at your shifter.

Nah, that's fuel for sure. The engine needs very little fuel to run up without a load; much more fuel to run up in gear. It's not getting enough fuel. Nothing "strangely" about it.

[Kenomac]

One more thought, is your prop completely free of growth? As in totally free and scraped clean? What does the bottom look like? Is it clean?

[Dockhead]

Originally Posted by Kenomac

One more thought, is your prop completely free of growth? As in totally free and scraped clean?

Yes, that's a very good tip. A dirty prop can be so hard to turn that the engine could choke like this.

[Kenomac]

Originally Posted by Dockhead

Yes, that's a very good tip. A dirty prop can be so hard to turn that the engine could choke like this.

Especially at slow speed and starting out. Which is why growth is the first thing I check, growth is the second thing I check, then third I check fuel. It doesn't take much growth to make a difference.

Did you ever get your dive gear working and yourself certified?

[tulsag]

If it was the shifter, I'm assuming that the linkage at the engine would not be moving. It is moving. And, it is doing exactly what it does when I have my wife shift from the cockpit and it works 80% of the time properly. It is the engine that is not responding, not the shifter or cabling.

Mark

[tulsag]

Prop:

Prop is perfectly clean. Boat just went back in the water with new paint and prop cleaning. The lag returned within a week of returning to the water. Dove it, prop is still clean.

Fuel:

We motor around the Med for 5-8 hours at a time and the engine works perfectly. Wouldn't a fuel delivery problem repeat itself at 2000 rpms motoring if it does it at throttling up from 800 'idling' rpms to 1,500 'testing the anchor' rpm's?

THE PROBLEM ***ONLY*** EXISTS WHILE THROTTLING UP (slowly, or quickly) FROM IDLE.

Mark

[Dockhead]

Originally Posted by tulsag

Fuel:

We motor around the Med for 5-8 hours at a time and the engine works perfectly. Wouldn't a fuel delivery problem repeat itself at 2000 rpms motoring if it does it at throttling up from 800 'idling' rpms to 1,500 'testing the anchor' rpm's?

THE PROBLEM ***ONLY*** EXISTS WHILE THROTTLING UP (slowly, or quickly) FROM IDLE.

Mark

Not necessarily - fuel delivery problems manifest in many weird ways. I would definitely try changing the fine filter and running from a jerry can.

[Captsteve53]

Just worked on Jeanneau 47 with a Volvo MD31A (62 Hp) with a very similar problem, found two issues

1) The fuel lift pump was way under pressure and fuel quantity being delivered, thus causing the injector pump to follow suit -slow to rev and had an issue obtaining full RPM, most injector pumps require around 4-6 PSI input in order to perform correctly.

2) Although the new fuel pump helped it was still not revving up quickly enough and still sluggish, I found that the owner had been playing around with the injector pump return line banjo bolt and had some how lost the return fuel line restriction valve (located in the return Banjo bolt assembly) once replaced the injector pump was receiving the full pressure of fuel and engine returned to normal operation,

Both symptoms were far worse obviously under load in gear but not so noticeable out of gear.

[Kenomac]

Originally Posted by tulsag

Prop:

Prop is perfectly clean. Boat just went back in the water with new paint and prop cleaning. The lag returned within a week of returning to the water. Dove it, prop is still clean.

Fuel:

We motor around the Med for 5-8 hours at a time and the engine works perfectly. Wouldn't a fuel delivery problem repeat itself at 2000 rpms motoring if it does it at throttling up from 800 'idling' rpms to 1,500 'testing the anchor' rpm's?

THE PROBLEM ***ONLY*** EXISTS WHILE THROTTLING UP (slowly, or quickly) FROM IDLE.

Mark

Good, then my bet is on a dirty turbo. Have you been revving it once every hour per Yanmar instructions in order to blow out the carbon produced by running at lower revvs?