Yanmar reluctant to start - sometimes..?

[mixmaster]

Our Yanmar 4JH2E developed a funny quirk 3 months ago on the 1st day of our one year cruise while trying to leave the Solent. It has happened intermittently since then.

When we try to start the engine, sometimes, and always when it hasn't been started in a while, it is very reluctant to start. Takes a few tries and there is always a large voltage drop. I know this because the GPS and chartplotter usually shut down. The engine turns over very slowly but after a few tries it has always started. If I shut it off subsequently and go to restart, the problem has never repeated itself.
We have have always managed to start, the problem has never occured at sea and besides the fact that it only happens after a day or two of non use, seems random.
We live on the boat so the engine never goes more than 3 days or so without starting.
I don't suspect the battery charge. Starter motor/solenoid?

Thank you.

 

[daveyw]

Are you saying it's cranking ok but just refuses to fire? We had a brand new 4JH4E fitted this year and we too are having problems. It has an electric lift pump that raises the fuel from a keel tank just below the engine. For some reason, when you go to start it, it fires up for a few seconds then stalls. It then takes 3-4 minutes of intermitant cranking to bleed the system before it will fire again. The Yanmar agent says the electric lift pump isn't up to lifting fuel from a keel tank!!! Sounds like "not fit for purpose" to me. 4 months later and Yanmar still haven't sorted it.

 

[misterg]

Our Yanmar 4JH2E .... The engine turns over very slowly but after a few tries it has always started. ...

If it turns over slower than it should, look for poor connections first:

Starter battery terminals + & -;
Starter battery Isolator switch(es);
Solenoid terminal (the heavy one);
Any link between the solenoid and starter;
Engine to starter battery -ve;
Any 'earth' straps used to connect the engine to 12v -ve.

Not clear if it always turns over slowly, or if this is linked with the problem, in which case, if it happens again, check to see if the isolator (if any) or solenoid are getting hot. If so, chances are that that is your problem.

Taking another tack, and this might apply to Davyw, too:

It's possible that you've got a small leak in the fuel pipe which is allowing air into the system and the fuel to drain back towards the tank. Standard advice is to check over all the fuel supply pipework, filters and bleed-screws and eliminate any and all diesel weeps - if fuel can get out, then air can get in (given long enough).

Andy

 

[mixmaster]

Thanks misterg. I'll check the fuel lines over in the next couple of days. Daveyw, your problem sounds different from mine. My hunch is that it will be electrical or solenoid but best to eliminate a "simple" fuel leak. . .

 

[misterg]

Would you mind clarifying whether the engine always turns over very slowly, or if this is part of the problem?

Ta.

Andy

 

[mixmaster]

Sorry, 19 out of 20 times it start on instantly but there is that odd time where it won't start and I have to turn the ignition key again. Turns over slowly then but starts in the end.

 

[Manuel]

I am surprised you are running your nav from your starting battery. Just check that's what is supposed to be happening. Sounds like bad connections from your battery to the engine starter. Begin by removing the battery connections, clean, Vaseline and put back. This needs to be done once a year anyway and you will probably see some signs of trouble if that was the cause. Feel all battery cables at connections and terminals for looseness. A nut might have vibrated loose. You need to sort this before going to sea, the problem will not go away.

 

[mixmaster]

I don't run nav from starter batter but sometimes start engine from house battery (600Ah!) It's not the battery connections because they were removed and vaselined very recently and happens when I start from either battey bank. Probably happens even less than 19 out of 20 times which is what makes it so hard to analyse. Can't really call out an engineer when nothing is wrong most of the time!

 

[Tranona]

There is a loose or poor connection somewhere. The connector on the main harness is a favourite one. Could also be a dodgy starter switch. Sytematic checking of every connection is the only way of finding it.