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Injection Limiter adjustment
On Thu, 20 Mar 2008 22:22:42 -0700 (PDT), "
wrote: On Mar 20, 5:55 pm, Bruce in Bangkok wrote: First, yes, fiddling with the governor can cause the engine to explode. Just to make sure we're on the same page, I'm not planning on messing with the no-load maximum speed limiter. That's just fine and the manual says, more or less, don't mess. I'm looking at the injection limiter which is also sealed but which shouldn't change the ultimate rpms and which the manual provides a method for adjusting... No, no, don't hold back, I can take it Really, thanks for the input. -- Tom. I finally located a 2GM20 manual. downloaded it from http://motoren.ath.cx/menus/yanmar.html and "limiter" IS a "anmar"word. The Manual quite emphatically states that the high speed adjustment and the Fuel Injection Limiter should not be adjusted and will void the guarantee if the seal is broken. The screw labeled "No Load Maximum Speed Limiter" adjusts the linkage to adjust the high RPM. The "Fuel injection Limiter" acts as a stop to limit the maximum movement of the fork that moves the fuel rack that determines how much fuel the individual injection pumps inject. If, for example, the engine is idling and you jam the throttle full open the Speed Control Lever applies force to the Governor Spring which forces the Governor Lever to pull the rack (in the injection pump) to the high fuel position and feeding more fuel to the engine which causes the engine to accelerate. When the engine RPM reaches the speed dictated by the tension of the Governor Spring the Governor Weights swing outward and force the Governor Lever back against the force of the Governor Spring to maintain the RPM selected by the position of the Fuel Control Lever acting through the Governor Spring. However, prior to the Governor Weights opening there is nothing to resist the pull of the Governor Spring so the "Fuel Injection Limiter" comes into play and acts as a stop to limit maximum movement of the Governor Lever before the engine accelerates to a speed sufficient to actuate the Governor Weights. I'm not sure whether the Fuel Injection Limiter has a spring loaded plunger in it or not. Detroit Diesel engines had a similar device but in their case it was to limit surge at idle. Backing the Fuel Injection Limiter out will increase amount of fuel during acceleration before the Governor Weights have a chance to react and thus the chance of over revving the engine is increased. Screwing it in will reduce the amount of fuel and the engine will accelerate slower then normal. I'm certainly not going to recommend that you violate the manufacturer's recommendations but if you are committed then hold the safety wired nut and remove the acorn nut. The screw should have a slot so it can be adjusted with a screw driver, if not scratch a line on the screw so you can tell how far you have turned it. First of all, with the boat securely tied to the dock (you don't want to be charging all over the ocean while you are trying to adjust the engine) try moving the throttle rapidly from idle to about half throttle, with the transmission in neutral. You should get a puff of black smoke and the engine should smoothly accelerate to whatever speed your throttle is set to. Backing the Fuel Injection Limiter out will increase the amount of fuel available for acceleration and therefore a bigger puff of black smoke. Turning the screw in will reduce the amount of fuel available for acceleration and reduce the puff of black smoke. A normally operating diesel engine always has a little black smoke when it accelerates. If you reach a point that the engine accelerates to a higher RPM and then settles back to a lower speed you have gone too far. Screw the Fuel Injection Limiter back in a bit. I would suggest moving the screw not more then a quarter turn at a time. Once things seem to work correctly try the same thing with the transmission in gear and make any necessary adjustment. Once you have the engine running properly when you accelerate to half throttle try idle to full throttle (carefully). Once you have the idle to full throttle acceleration adjusted both in neutral and in gear you should have the engine correctly adjusted. Bruce-in-Bangkok (correct email address for reply) |
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