Yanmar 4JH4AE starting problem
Nov 3, 2011 1:09:44 GMT
Post by miketonner on Nov 3, 2011 1:09:44 GMT
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.
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.