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6LP-STZE not accelerating under load

Wallaby

New member
I have a pair of 300hp 6LP-STZE Yanmar diesels powering a 33' Cat. The motors were running exceptionally well until recently. I decided to have the injectors serviced as routine maintenance as they had not been done for 15years and the motors have done 1000hrs. Since installing the serviced injectors the motors have been down on power when under load. The motors will not accelerate beyond 1800 RPM when operating them individually. The injectors have been validated as correct. I have run some test with regard to turbo boost pressure and in particular the boost compensation on top of the fuel pump. The turbo will produce 2.3 bar at WOT at 3800RPM (both motors working together). Interestingly the boost pressure does not come off zero until about 2200 RPM, therefore the boost compensation on top of the fuel pump is not scheduling more fuel until 2200. Problem is the engines will only deliver 1800rpm when operated individually. Prior to changing the injectors the motors would accelerate to 3200 plus without lag when operated individually. I am trying to determine when the boost should come in and what boost should be expected at various RPM. I am getting 2.3 bar at WOT. Has anybody seen or heard of this issue previously or has anybody got any ideas where to go next. Cheers Mike.
 
Check the valve adjustment. This has to be done with the engine cold. At least 24hrs cold. FYI some of the Yanmar manuals have the incorrect valve lash published.

Valves out of adjustment will cause this problem.
 
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