Yanmar 4J stalling

[RAP77]

My Yanmar 4Jh3E has suddenly started to stall when I reduce the throttle setting quickly. It will idle perfectly if i reduce the throttle slowly.
It will not start unless I open the throttle, it just gives a quick burst then dies.
This is a very new problem previously it would start first time from cold with the throttle set at idle.
Both fuel filters are new. The idle stop on the fuel pump is unchanged and securely locked.
I have done nothing to the engine except change the fuel filters and impellor.
I have checked the fuel lines for air leaks but not found any.
I am hoping to get some pointers to possible causes before calling in expensive experts
It has 1500 hours and is 10 years old
Thanks

 

[Cariadco]

Likely Suspect??

I'm inclined to suspect the fuel pump maybe slighly blocked on one or two of the outlet ports to the fuel lines feeding the injectors.
However, I'd advise an inspection by a good diesel mechanic, before removing the pump.

Hope this helps,

Regards.

 

[misterg]

It sounds like the governor is sticking. Don't know whether this is a common problem with these, though.

Andy

 

[RAP77]

Thanks - I will change the filters and ensure there is no air leak. If that fails it will have to be an engineer to check the fuel pump.

 

[eagleswing]

check the throttle cable too..

also check that the morse cables controlling the throttle have not become stuck in the shield. you can lube the cable ends both at the helm and at the wire terminating the c able on the engine with lithium grease. be sure the throttle cable is running smoothly within its housing to the attachment on the engine block .

10 years 1500 hours is young to have a fuel pump problem, those diaphragms supposedly last 10,000 hours.
if you had an air leak you'd be running rough or cutting out all the time not just at low rpms. you might also set your idle a little higher, maybe 850-900 till you get this sorted out.

 

[Heckler]

Bleed the fuel system again, if that wont cure the problem put another new fuel filter on and make sure the seal is seated correctly.

+1
If it came on after messing with the filters it is a good guess it will be them.
Stu

 

[vyv_cox]

Rap77 have faith, even the aussies agree with me

http://www.exploroz.com/Forum/Topic..._-_wont_idle_after_replacing_fuel_filter.aspx

its a problem thats as old as the hills along with the solution.

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[RAP77]

Recent posts have reminded me to say thank you to all who responded to my post regarding stalling Yanmar 4JH.
I have finally resolved the problem (touch wood)
Following all your advice I changed the filters to no effect but I then dismantled and remade all the connections in the fuel line one by one.
The guilty party was a connection to the vacuum guage cured by resealing the union. Hey presto all back to normal.
There must have been a very small air leak not enough to stop the engine once it was running but enough to drain the fuel over several days.
Thanks