Yanmar 4JHE Problems

[Another Day]

Last week I changed both my fuel filters, the Racor and the spin on Yanmar one. Cranked up after little bleeding and seemed fine. So come the weekend we were going to go off and cranked it and let it run awhile, turned it off and then did not want to fire. So figured still a little air in it and went and bled and cranked up easy enough. Went to get some fuel at the dock next door and it was idling fine. We back out into the river and then when started going forward noticed it would not throttle up. Seemed to be choking down. Figured still had some air. Could put in neutral and it would rev up. So did that a few times and put back in gear. Went a bit and figured it would clear itself out. It would only get up to around 1700-1800 RPM. At this stage thought maybe something was wrapped around the prop and binding it so went swimming to see. Nothing on prop, but it was fouled somewhat with barnacles. Cleaned that while there.

When tried to crank this time there was some racket in the back of the engine with what sounded like metal hitting metal type noises, so I shut it down. Looked down at the drive train and saw nothing apparent. Shifted the trans up and down a few time and didn't seem bound. Tried again and still doing it so shut it down and called Boat US to tow us in. First time in all these years ever used the tow policy which was good to have.

Someone at the marina who used to work on engines said he had seen bolts on the flywheel on a Yanmar back out on one and get into the gear box cover before. Can put in neutral and spin the shaft and don't hear or feel anything, so flywheel thought may make some sense. One thing also noticed yesterday when looking at it was, the air cleaner had some oil like dripping coming from it and when I removed it had a handful of oily sludge in it. Not sure if that was caused when it was so loaded it was blowing fuel back. Was not doing that before because that area stays clean and could see it had dripped on the pan. Oil on the dip stick looked normal. Not sure what to think or where to even start. Gearbox is a Kazaki KBW20.

Prior to this always starts fine, no shifting issues. Ran good


Any thoughts would be appreciated.
Thanks

[a64pilot]

I have had Diesels that sounded like Hell when there was air in the fuel system, knocking like the Devil, I assume it simply messes with timing as well as of course fuel delivery. I'd bleed it again, from the top of the secondary filter of course, crank it and bleed each injector at idle.
I've never had to do that with My 4-JHE, but I have had to do that on Farm tractors plenty of times.
Seeing as how this started with a filter change, I'd be sure to rule that out before I started tearing into things.


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[transmitterdan]

The 4JHE is self bleeding I think. I have never had to bleed our 4JH3E when changing filters. Just fill the filter with fuel before installing and fire it up.

[Arthur Garfield]

@transmitterdan,never had to bleed because you always pre-filled fuel filters.Always best pre-fill oil filters also.

Hi Another Day,

Welcome to CF !

Sorry to hear about your fuel/engine travails!
Sounds to me like air in line somewhere prob.
Did you fill filters with clean diesel fuel before mounting??
I don't know of your engine type speciffically but I have never heard of a "automatic bleeding " diesel engine.Wonders never cease !
All things equal your situ most likely air in fuel system.Sometimes a diesel will buck and make all manner of ornery noises when air in line(s).
Seems you ran out all the fuel in lines from filters and injection pump.
Must be a little hand pumper to fill sys to injectors.Get yourself special line wrench to open line into injector for future bleeding.


All the Best

[boden36]

Transmitter Dan is correct, a moderate amount of air in the line will just go back down the return line. I have even started mine without bleeding when it had sucked one tank dry.

Regards,
Richard.

[Arthur Garfield]

Another Day,

One possibility I neglected to mention could be a problematic lift pump in tank (electric) or mechanical mounted to block(diaphragm pump). though doubt these the problem.
Air somewhere.


All the Best

[Another Day]

I'll try and bleed it at the injectors and see what happens. Will say I did not fill the Yanmar filter with diesel when I put it on. May have been my mistake. The Racor was full. Thanks for all the input. Hope for the best - will let all know how it goes

[a64pilot]

If it's air in the fuel related, as soon as you crack the "B" nut on an injector, if it's the offender, the noise will immediately go away, engine will pick up a roughness though of course.

Is there a "flex plate" between the engine and transmission? I've seen a cracked one of those knock just like a rod bearing does. This noise, is it rhythmic or sporadic?

Myself I never pre-fill a fuel filter, it's unfiltered then, and it's just to easy to pump it full before starting the engine, even using the wobble on the mechanical pump it only takes 30 sec or so.

[Another Day]

There is not a flex plate. Noise was there in gear or out. Given access was hard to tell exact location of the noise. Took the floor plate out and can now get at the back of the engine and gear box. Will try to crank tomorrow when have someone who can help turn it on and off if needed while In the hole. Plan to try bleeding also

[Peter200]

Welcome to CF.

I had a similar problem with my Yanmar 75 hp, working great one minute then revs up fine in neutral but in gear 1800 revs max. After checking it was down to the electrician I had had on-board a couple of days earlier running some wires. He had managed to knock the fuel cut off linkage on top of the fuel tank accidentally so it was restricting the fuel flow to the engine. I noticed in the cockpit that the pull lever was about two inches out. Putting two and two together and coming up with four this time this solved the temporary problem.

If it cannot be fixed with a hammer it must be an electrical problem

[Another Day]

Which would be the B nut - larger on the bottom or the smaller one on top?

[a64pilot]

Originally Posted by Another Day

Which would be the B nut - larger on the bottom or the smaller one on top?

The "B" nut is the top nut, the nut you remove to remove the line, it's probably more correctly called something else, B nut is an aircraft term and I mix terms pretty badly.
Anyway, I'd suggest first gently loosening them and re-snugging them back down with the engine off so that it's easy to loosen them with the engine running.
These things do not require a great amount of torque, and I believe if you over tighten them you actually ruin the flare on the line and can cause a leak, just barely loosen it and you will hear and feel the engine suddenly be running on one less cylinder, let it run that way for 4 or 5 seconds and tighten the line, go to the next. Put a rag around it to catch the fuel, it will leak out of course, but not that much fuel actually, it's not like loosening a fitting on a water hose, injectors only get a very short spurt of fuel every other revolution of the engine of course.
May not be required, but easy to do, costs nothing and you can scratch an item off your trouble shooting list.
I usually trouble shoot the easy and cheap items first, even if something hard and expensive is more likely, sometimes I get lucky and its and easy and cheap fix.

[thegui]

Hi
It almost sounds like the engine is being starved. Check the screen at the top of the dip tube. this should be located on top of the fuel tank. Debris often gets sucked up into the tube and swells slowly cutting off the flow.
Worth a try.
Best of Luck.