Yanmar 4jh4-hte

[stiknstring]

Although I have this 110hp lump installed in my sailing boat, I thought the best people to approach over my constant engine problems were probably here on the Motor Boat site. For the past three years, since I brought the boat down to the Med, I have had the same problem : After any long passage under power, when I reach the destination and need to slow the boat down, the engine responds to a reduction in revs by cutting out completely. Today was just another example coming into the marina at El Arenal in Mallorca. The strange thing today was that I could get the engine running again (albeit a little reluctantly) and it would then engage into reverse but then die out when I put it in forward gear.

I have over the years had the gearbox removed and a new clutch put in, changed the volume of air that comes into the engine compartment (suggestion being that the original blower was too small for this larger engine and the heat in the Med might have been a factor) and last year, I had an engineer from the UK, who I much respect, fly down to the boat in Valencia to troubleshoot. He found that I had been running the engine at too low revs (1800-2200) and as a result the turbocharger had coked up. After a lot of work, he managed to clear the carbon deposits and last year the engine worked like a dream. As I said, this year (today), after the first passage (151 NM), the same problem occurred.

Have any of you had the same issues? Does this look like a recurrence of the coking problem (I have since run the engine at the recommended 2500 RPM), is it another gearbox issue, fuel filters clogged (I discount this one but it was suggested today).

I am tearing my hair out on this one, and yet I am sure there has to be a relatively simple (if expensive!) solution.

Grateful for any suggestions/comments

many thanks in anticipation. Alan
Read more at http://www.ybw.com/forums/showthrea...-what-are-we-missing-here#otP1fSGRZ2ljexjE.99

 

[Talulah]

Have you tried replacing the diesel tank breather? After a long run the diesel tank could be creating a partial vacuum.

 

[stiknstring]

That is an interesting one - I did wonder if there might be some sort of vapour lock, but then why would it manifest only when trying to get forward gear. It does chime though with the heat and other weather variables we didn't experience in the West country before coming here. Thanks for this, very useful

 

[Bandit]

I would think fuel delivery restriction, over propping or engine room temperature

 

[stiknstring]

Thanks Bandit. It is a mystery to me so, I' m not dissing any of the suggestions here, just commenting - fuel delivery -we are still able to move along at full flank speed (9.1kts!), so not sure that is the problem, the prop has been on since new and we didn't have problems before we got down here to the Med - but the temperature suggestion is also a very logic- tempting answer, maybe coupled with the comment from Talulah (above). I am no mechanic and barely know my way around a diesel engine, but could it be that the high ambient temperatures currently (40C+) and a breather pipe issue are each contributing to the issue? I don't suppose that pro-tem, if the issue occurs again, just releasing the diesel fuel filler cap for a while would "reset" the vacuum mentioned in Talulah's post?

At the back of my mind though is the fact that the turbo was coked up in 2015 - maybe, while it was cleaned out at the time, some lasting damage was caused.

Not easy these intermittent faults! As a test, I started the engine today and engaged fwd gear (and reverse) - instant response and all good, but the gremlin still lurks. Looks like we may have found an engineer to turn out Monday, so I will also ask these same questions of him. Meantime, the Mistral of today returns in earnest on Tuesday/Wednesday, so looks like an unscheduled holiday here in Mallorca for most next week. Not too shabby if we can get to the bottom of this problem as well!

Thanks to you for your advice/ assistance - it is much appreciated, Alan

 

[Avalon]

This may or may not be helpful. We have friends who own a 50 odd foot sailing boat with a similar sized Yanmar auxiliary. Since sailing down from the UK to Portugal they have for several months experienced intermittent problems when running the engine at low revs. Repeated attempts by various engineers to resolve the problem were inconclusive.

If I understand correctly, they now believe that the following is the case:

Unlike most engines, on the Yanmar the fuel lift pump and injection pump are combined.

They believe that the fuel lift component is not working correctly, but this cannot be replaced separately. Replacement or reconditioning of the combined pump would be a very expensive exercise, but is the long term solution to the problem.

In the interim, they have fitted an electric fuel pump before the Yanmar pump. This workaround seems to be doing the trick for now.

Needless to say they had previously tried all the likely solutions relating to filters, pipes, tanks, breathers etc., even fitting a totally separate fuel system to supply the engine.

Hope that helps!