Yanmar Starting

[noelex 77]

I have just installed a new Yanmar 54hp engine. It is running beautifully apart from a slight problem when starting. It will start immediately run for a few seconds then stop. It is then slow to start (5seconds or so of cranking) then runs perfectly.
My diagnosis is that there is a small air leak in the fuel system.
I have swapped the generator fuel line for the main engine and the problem persists. This eliminates a leak in the primary fuel filter fuel shut off valve etc.
This means the leak must be in the high pressure part of the fuel system so a leak should be visible but after a very careful look I cannot find any fuel leak. I have also tried tightening the secondary fuel filter and all hose clamps on the fuel lines.
Where should I go from here any suggestions appreciated. Is it possible there is some other problem? OR some internal leak?
The engine installer was fantastic but I would have to turn around and backtrack to get back to him, so I would like to solve the problem myself if possible.

[never monday]

the leak shouldn't be on the high pressure side.

[jcmcdowell]

We just finished a minor/major refit on our CSY 33 and when we dropped her back in the water I had the same problem. Ran fine for about 10 minutes then died. I would bleed the lines again and it would start right up then die in 10 minutes (or less).

We have a 27hp Yanmar. My best guess is there is air in the fuel filter on the engine. Keep bleeding the fuel lines and it will stop.

You probably know this but you bleed the Yanmar where the line hits the engine AND after the fuel filter before it hits the injection pump.

Another note- mine you can open the compression per cylinder which takes a huge load off the engine. I start the engine with one cylinder engaged and then kick on the other two. Really Helps alleviate battery drain trying to start the engine under compression.

Check your owners manual on bleeding.

Best Regards,

[noelex 77]

Originally Posted by never monday

the leak shouldn't be on the high pressure side.

Thanks for the diagnosis. Does this mean the described symptoms can only occur if the leak is before the electric fuel pump?
If so its more of a puzzle as I have completely swapped the low pressure side (Primary fuel, filter fuel shut off, all hoses and fuel tank pickup are all different for the generator) and the problem remains unchanged. (The generator is a Nanni 15 hp DC generator and runs without stumbling on both fuel systems, but it maybe less sensitive to air)
If its not the high pressure side and not the low pressure side where is the air getting in?
Not trying to be smart and I appreciate all advice, but still puzzled.

[never monday]

The leak is between the inlet on the Yanmar and the high pressure pump most likely.

[Badsanta]

I would have trouble starting after sitting over night or several days, but after starting it would be fine the rest of the day with several normal start cycles.
On day I was explaining this to a yanmar guy at the bar (I bought) he explained that some have problems with the height of the fuel tanks and some after sitting a bit the fuel will slightly back syphen. Causing it to quickly start then dieing after 5 seconds or so, and restarting and running fine the rest of the day, with it starting all over the next time it sits. The fix he told me was to use the manual lift pump handle next to the secondary fuel filter and to pump this 20-30 times and then try to start ,this seems to work for me. Also I dont have glow plugs, so when colder I open the decompression levers give it full throttle and crank it for 5 seconds. I then close the levers back off to 1/4 to 1/2 throttle and crank it. Starts right up.
I hope that helps some. Al

[orion1]

Had a similar problem after 3 gm 30 f was haulled out with boat for 3 months. It would start right up as normal but would run so rough at idle it would need to be shut down. It would then start normal and run fine. If left off for hours it would repeat the dance. After a week of working with it, it started working normal. I discovered that the idle needed to be adjusted up.

I had rerouted the throttle cable during the haul out and did not get the adjustment dead on and the idle was way too low when cold.

[noelex 77]

This forum is great what did we do before the internet? Thanks everyone for taking the trouble to reply and keep them coming. To clarify a few answers:
The fuel goes from the tank to the fuel shut off valve to the primary fuel filter to the electric fuel pump(this is part of the Yanmar engine and seems to be used instead of a manual lift pump) to the secondary fuel filter to the high pressure pump to the injectors then the excess back to the tank via the fuel return line.

Originally Posted by never monday

The leak is between the inlet on the Yanmar and the high pressure pump most likely.

Do I understand correctly you think the leak is most likely between the electric fuel pump and the high pressure pump?

"a yanmar guy at the bar (I bought) he explained that some have problems with the height of the fuel tanks and some after sitting a bit the fuel will slightly back syphen. Causing it to quickly start then dieing after 5 seconds or so"
This sounds exectly like my problem. I will try operating the lift pump before starting as a tempary fix, but I hope that this is not necessary long term. The lift from the fuel tank is not excessive, indeed the generator sits above the main engine and manages to lift the fuel twice the height.

"Ran fine for about 10 minutes then died"
I think this may be a slightly different problem. Mine will start then die a few seconds later.

"It would start right up as normal but would run so rough at idle"
I think this may also be a slightly different problem my engine idle has always been very smooth.

[never monday]

What model Yanmar is this 54hp? exact #, please.
Electric pumps are not common on the 54 I'm familiar with. There should also be a return line to the high pressure pump.

A few things are concerning me. How does the electric pump get it's power? Is it safety controlled by the oil pressure switch?

[noelex 77]

[quote=never monday;227262]What model Yanmar is this 54hp? exact #, please.
It is a Yanmar 4JH4AE with the ZF30M gear box (shaft drive). The electric fuel pump is a round metal canister that gets its power from the engine wiring harness. I presume it operates full time when the ignition is on. It was standard with the engine. I assume it is used by Yanmar instead of a cam operated mechanical lift pump. There is also a push button mechanical lift pump on top of the secondary fuel filter used for priming the fuel system.

[noelex 77]

[quote=never monday;227262] There should also be a return line to the high pressure pump.
Yes sorry I forgot that one. The high pressure pump has high pressure fuel lines going to the 4 injectors and fuel return line back to the high pressure pump. The last injector (furthest away from the high pressure pump) has a fuel return line back to the main tank.

[never monday]

those must be EU spec parts. Can you post of send me a pic of the electric pump and the side of the engine with the injection pump. I'm trying to see if they did something they did on the YM series.

[noelex 77]

Originally Posted by never monday

those must be EU spec parts. Can you post of send me a pic of the electric pump and the side of the engine with the injection pump. I'm trying to see if they did something they did on the YM series.

Taking a picture now. Thanks for your help.

[noelex 77]

http://i169.photobucket.com/albums/u...x/IMGP0809.jpg
http://i169.photobucket.com/albums/u...x/IMGP0809.jpg
http://i169.photobucket.com/albums/u...x/IMGP0810.jpg

[never monday]

email me the full size of the silver can/fuel pump and the injection pump. Plus if you can move the fucus of the injection pump picture down to include the manual pump it would help.

inlandmarinediesel at hotmail dot com