For the Yanmar experts.

I have a friend with a similar problem on a Yanmar. IIRC it took taking the high pressure pump off and having it serviced in an approved workshop. I'll ask him for more details.
Edit: confirmed. Very similar symptoms to the OP. Solved by a rebuild of the injector HP pump in a specialist shop in Lisbon (Bosch).
 
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To eliminate the stop solenoid how about putting your hand over the air inlet to stop the engine then see if it restarts?
 
Rappey said:
To eliminate the stop solenoid how about putting your hand over the air inlet to stop the engine then see if it restarts?
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I will make a wooden cap with the same size bore as the turbo intake - I saw a fellow apprentice stick his hand over a 6 cylinder Ford lorry diesel intake.

It gave his palm a nasty suck................................
 
Good point about the suction. Mines around 38 hp so no where near the suck.
My stop lever actually speeds up the engine? ? So I stop it with hand over air intake
 
Fiddlesticks said:
Injection pump. There's a long thread here. Apologies if not related, just sounded similar.
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Thanks for that, read most of it but nearly all posters had poor running.

Our Yanmar runs perfectly once started, and, just to make it a real bastard to diagnose, the starting failure is completely random and irregular.

I shall be looking at the stop solenoid and wiring next, eliminating things one by one as I go along.
 
Do you still get the problem if you don't let it run long enough to get warm? Basically is it temperature dependent?
You have found fuel cracking the injector pipes when it won't start, don't see how it can be cutoff solenoid in that case.
Older ford diesels have a common electrical fault with the injector pump, won't start. You still get flow cracking the injector pipes but my understanding is the pump pressure is too low to open the injector. Is it possible that type of pump will produce flow but not enough pressure to open the injectors?
 
Another good point, thanks.

The non start is only at operating tempreture, is random and irregular.

When cranking during a non start episide, it almost, but not quite, lights up. To the extent it overspeeds the starter motor. You can hear it driving, as the engine almost starts you can hear the note change as it is driven.

The injectors have never been checked but when started the engine is perfect in its running, It will take full RPM at WOT for ten minutes against the springs and will run without missing a beat for an hour, in ahead, 2200 RPM, against the springs. No smoke of any colour, ever.

From cold the start is almost instantanious, you hardly need to crank it at all. If stopped when it does not suffer this random and infrequent non start, the same when restarting. Almost instant.

Which is why it is so bloody annoying!
 
rotrax said:
Another good point, thanks.

The non start is only at operating tempreture, is random and irregular.

When cranking during a non start episide, it almost, but not quite, lights up. To the extent it overspeeds the starter motor. You can hear it driving, as the engine almost starts you can hear the note change as it is driven.

The injectors have never been checked but when started the engine is perfect in its running, It will take full RPM at WOT for ten minutes against the springs and will run without missing a beat for an hour, in ahead, 2200 RPM, against the springs. No smoke of any colour, ever.

From cold the start is almost instantanious, you hardly need to crank it at all. If stopped when it does not suffer this random and infrequent non start, the same when restarting. Almost instant.

Which is why it is so bloody annoying!
Click to expand...
As it nearly goes some diesel is getting in but perhaps not atomising correctly to fire in the normal way & the introduction of the minute bit of ether gets it away.This is indicating something not quite right intermitently in the pump
common to all cylinders - had one experience with fail to start on a rotary pump which turned out to be the cam ring surface had broken up & the swarf jammed the stop solenoid in the stop position occasionaly.
I can understand your frustration
Jim
 
bristoljim said:
As it nearly goes some diesel is getting in but perhaps not atomising correctly to fire in the normal way & the introduction of the minute bit of ether gets it away.This is indicating something not quite right intermitently in the pump
common to all cylinders - had one experience with fail to start on a rotary pump which turned out to be the cam ring surface had broken up & the swarf jammed the stop solenoid in the stop position occasionaly.
I can understand your frustration
Jim
Click to expand...

Looking like it might be in that area.

Of to the boat tomorrow, will be putting some of your suggestions to use.

Thanks again guys.
 
1) Can't say all those people hinting at dirt in the injection pump somewhere are wrong.
Is there some tiny hidden filter?

2) The odd stalling behaviour fixed by upping the idle speed suggests some sort of governor issue?

It has to be something which is common to all the cylinders. (?)
I'm not familiar with the injection pump, but I would be checking that whatever meters the fuel moves as it should, when it should.
I know they tell mechanics never to touch these things.

Crackpot suggestions for when you run out of logical things to look at:
Can the facet pump stop things working if it doesn't get enough volts due to the starter cranking?
Try running gravity fed with known good new fuel?

Can you ascertain whether it is actually injecting fuel? If it is, suspect the timing?

My LandRover mate suggests checking the returned fuel is not aerated, something about fuel draining away from the spill area of the injectors? Not sure what that's about TBH. But I pass it on in case it jogs someone else's thoughts.
 
rotrax said:
Looking like it might be in that area.

Of to the boat tomorrow, will be putting some of your suggestions to use.

Thanks again guys.
Click to expand...

Hi Rotrax
Can you let us know if you finally solved it? We have the same engine and the same symptoms. Ours in a 2005 Beneteau 523. Driving us slightly mad in Wellington, NZ.
 
I have a Yanmar 4JH2. The only time I have ever had difficulty starting it was when the stop pull was not entirely pushed back to its proper place.
May be some issue with the stop pull/solenoid?

It is 22 years old and has probably done quite a few hours.
 
MikeNZ said:
Hi Rotrax
Can you let us know if you finally solved it? We have the same engine and the same symptoms. Ours in a 2005 Beneteau 523. Driving us slightly mad in Wellington, NZ.
Click to expand...


Resolved the problem to some extent, the starting problem has not occured for some considerable time.

I have no idea why.

But then we have been alongside since October, not being able to use the boat due to lockdown/travel limitations.

Were you in Evans Bay yard and subsequently in Chaffers Marina in Febuary March 2020?

If so I spoke to you.

We have Ella, a Steel Hartley 32 in Evans Bay Marina.

Who knows when - or if - we can return.
 
Hi Rotrax

I also the same engine, and exacly the same issues. First thing I also did was to adjust up the idle. Then it dont stalls. But still bad at warm start. I removed the termostat to run the engine a little cooler. That helped. ( I am in Caribbean, so the engine wont get to cold..) I had it like this for a year. No problems. Last week, I put back the termostat, cause my wife was complaining that she did not get hot enough water for the dishes. (She complained the hole year) The problem came back. Now it wont start when warm.. Like yours, just sometimes. I was sure it was cases by the CSD (cold start devise) on the inj. Pump. This is a water heated wax-soleniod that expands when it get hot. Then it pushes a cam, and changes the inj. timing in the inj. pump. I have now adjusted the CSD so shall not push the cam, and I will test this the next days.

Andreas
SY Alissa
 
Interesting possibility if there is a waxstat controlling the cold start; the other thing that the symptoms suggest is sticking or even weakened springs in the governor, although I'm entirely unfamiliar with the Yanmar so no idea how easy that would be to access.
 
Resurecting this old post as I am now pretty sure the Rotary Pump head is at fault.

I suspect that when the fuel is hot it loses viscosity and the pump cannot generate enough pressure to open the injectors against their springs. The injectors are held in place internally, under the four valve OHV valve gear, so not easy to access

Bummer!

I shall try and identify the model of pump fitted, get some part numbers and check parts supply before removeing the pump.
 
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