Yanmar 4JH4AE starting problem

[miketonner]

Symptom: Engine needs a lot of throttle to start and then dies immediately. Problem only evident when engine has not been started for several hours.

Engine affected :4JH4AE 54HP (& possibly larger HP versions up to 110HP) circa 2008. Only versions with fuel filter priming pump (see picture).

The engine on my 2009 42DS (built 2008) became difficult to start after only 2 seasons. The engine would start but immediately die and then required full throttle and some cranking to get it running.

The problem seemed to be due to air in the system but everything from tank onwards seemed tight & leak free. The engine would start perfectly if it had been run in the past 10 hours or less.

I reasoned that the shaft seal on the pump might be passing air as the tank is fitted lower than the filter. To test this idea, I bled the system and plastered grease around the pump shaft. It worked perfectly for about a week. I also ran into someone who had reported the same problem to his Yanmar dealer. He confirmed that it was a known problem on some engines made in 2008 (and other years for all I know).

Yanmar fixed the problem under warranty and said that it only affected a few 4JH4AE engines. However, I've spoken to 2 other owners with same problem so thought that it would be worth sharing.

My engine now starts perfectly without touching the throttle. No selecting full throttle, trying to start and then wiggling the throttle to keep it running.

The "fix" was to replace the small priming pump on top of the fuel filter. The new unit has a "T" which bleeds air back to the tank return line. Filter changes used to require bleeding by use of the priming pump and bleed screw. I think that the new version just needs the ignition circuit on for a few minutes until the electric pump pushes all the air out.

[Tafika II]

I have been having a similar problem. I think I will contact Yanmar for their comments. Good to know the crazy things are not only on my boat. Thanks!

[Mistroma]

I spoke to one other person who said that his engine had been fine since buying the boat in 2008. However, as soon as I described the problem he recognised the symptoms immediately.

He'd just assumed it was normal and had become used to using a lot of throttle to start.

Another chap said that Yanmar had only supplied a replacement filter top and the dealer had to go off for an extra bit of fuel hose. So slight delay getting it back out to his mooring.

I made a point of asking the dealer to make certain that Yanmar included any extra hose. So mod. was installed in 20-30 mins.

Unfortuately, I don't have a picture but the filter fitting now has a flat top with a T-piece. I think that the existing fuel return line is moved to the T-piece and a new section is needed to connect the other side of the T to the original return line connection.

[paradox]

We ran into a similar problem and discovered that the clear engine hoses were leaking. We eventually replaced all the engine hoses and resolved the issue

[Mistroma]

My starting problem was certainly related to the pump on top of the fuel filter. This sounds like completely different problem.

I wasn't aware of any clear hoses on the fuel lines so will check them as well. Where were they fitted? All the fuel lines I've seen on my 2009 42DS are black.

[willmington]

Same 2008 same engine same problem fixed with updated fuel filter head without pump in the same way. All Fine.
David Willmington

[sailingbaylana]

Anyone have the part number for the top fuel filter assembly I have to replace on my Yanmar 4.  I am having the same problem. It is a 2008 jeanneau and it takes a lot of cranking to start.   I have the old model with the bleeding pump on top of the fuel filter.

Thanks

Ace

[Mistroma]

Hi, I did the original post (no idea why it didn't come up as Mistroma). I'm in Denmark at present but should be back in Scotland tomorrow and able to get access to old files more easily. I'll have a look but seem to remember someone else asking for the part no. last year. I don't think there was a part number on the new filter head. I think that I couldn't find any reference in the old documentation either aan the invoice just said "replace filter head FOC" or similar.

I'll check anyway in case my memory is playing up. I seem to remember hearing that they'd just fitted the fuel filter housing from the newer 4JH5 engine.

[Tafika II]

I think these are the pages you are looking for.

[Mistroma]

Tafika, OP is asking about the part no. for the newer filter head. Diagrams you posted seem to be for the water separator and the older filter head with the integral pump.

The seals on the older filter head pump piston have been known to leak, that's what caused problems with my engine in 2011. Lack of a pump does mean you need to run the electric pump to prime after changing, not a big deal. The engine does now start immediately even after 6 months storage, let alone 4 hours with old filter head.

I might be able to find more information when I get home tonight. Not certain but I might have some information about the newer engine (4JH5?). I think it uses this style of filter head.

[Mistroma]

I had a look through my records and could not find a part number as the invoice lacked that information. I don't have manuals for the newer engine either, just the older models. Sorry, but can't locate the part number.

I did find several close-up views of the newer filter head and I was correct in thinking that there were no part numbers visible anywhere.