First time running up this season on with a Yanmar 3GM30FV. My idle speed will not go below 1600 rpm. I had some corrosion develop around the the governor linkage which stuck my throttle, however, i cleared that up with some lubricating oil and elbow grease. The engine runs fine up to 3600 rpm as specified. I just replaced the 180º mixing elbow on the exhaust due to a blockage in the passage for cooling water. One of my thoughts is the idle was progressively adjusted as constriction increased in the old elbow, increasing exhaust backpressure. I'm hung up on the fact that a backpressure problem would affect the top end of the rpms, not idling speed. Any thoughts? I bought the boat last summer and noticed the cooling water problem develop after a few months. I don't want to haphazardly adjust the idle stop, considering I've never had a diesel that needed idle adjustment as often as a gasser carb retune.
Yanmar idle speed correction
- Thread starter blackeydp
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In addition to the governor, which usually is for the HIGH end stop, I would suggest looking at where the cable comes to the engine and there are most likely low rpm stops there, too. Sounds like you know about it and the PO could've done something there for the reason you mentioned.
I had a similar problem on my 3GM and after searching for the problem I found it to be the throttle body (lack of a knowledgeable term) was stuck. You can find it on the engine side of the throttle cable, make sure it moves freely, I cured my problem with WD40. Just move it back and forth by hand until it moves freely and resets to the idle screw on its own.
It is still very sticky. I believe it got a good dousing of salt water, which may be my fault when I pulled the intake hose off the water pump. I can not move the linkage by hand. I can adjust it with the leverage of the engine controls at the helm, so I will give it some more oil as you suggest anyway. It moves through what I can tell to be its full range, but it does not seem low enough to make it to idle. Time to experiment....
The lever arm that the throttle cable hooks to fits on a shaft that goes into the injection system. Although you cant remove the shaft (at least I wouldnt), you can remove the lever. I coated the entire area with lithium grease, then reattached the lever and exercised it. Loosened the whole area up and throttle works much easier. The shaft is splined so you have to put the lever on in the right spot to get the proper throw. Line it up so it is touching the idle stop screw and try it. You can adjust from there to get full throttle and proper idle rpms.
A small but not insignificant point of understanding.. The "throttle" on a diesel sets a desired RPM in the governor (changes the RPM set point).. The governor then adjusts the fuel injection pump to achieve that RPM. Problems with idle and full rpm many times are caused by cable friction..too much or too little ..
Specified idle minimum is 850 RPM.. There is an idle stop on the speed control lever at the engine.. If the lever is hitting that stop, the stop needs adjustment.. If the cable is not pulling the lever all the way back to the stop, disconnect the cable and see if you can move the lever by hand back to the stop.. If yes, cable adjustment or too much friction.. if no with cable disconnected,speed control lever friction..(crudded up from corrosion?) .. There sometimes is a "squeezer" that squeezes the cable cover to add friction.. if it was set long ago and the cable has more friction now, the squeezer may have to be adjusted..
in steps: Engine off.. disconnect the cable. Move the control lever at the helm should be smooth and have some friction, but not a lot. At the engine pull the speed control lever back to the idle stop.. it should be free enough to move there easily. Put the speed control at the helm to idle. hook up the cable in that position with the engine speed lever still on the stop. .. advance the helm throttle slightly and start the engine. it should be idling at a low speed.. If not, the stop needs to be set lower.. Hope this helps.. Good luck with it.
Specified idle minimum is 850 RPM.. There is an idle stop on the speed control lever at the engine.. If the lever is hitting that stop, the stop needs adjustment.. If the cable is not pulling the lever all the way back to the stop, disconnect the cable and see if you can move the lever by hand back to the stop.. If yes, cable adjustment or too much friction.. if no with cable disconnected,speed control lever friction..(crudded up from corrosion?) .. There sometimes is a "squeezer" that squeezes the cable cover to add friction.. if it was set long ago and the cable has more friction now, the squeezer may have to be adjusted..
in steps: Engine off.. disconnect the cable. Move the control lever at the helm should be smooth and have some friction, but not a lot. At the engine pull the speed control lever back to the idle stop.. it should be free enough to move there easily. Put the speed control at the helm to idle. hook up the cable in that position with the engine speed lever still on the stop. .. advance the helm throttle slightly and start the engine. it should be idling at a low speed.. If not, the stop needs to be set lower.. Hope this helps.. Good luck with it.
If the shaft into the injector pumps is moving full travel it should idle arond 850 rpm. This shaft has a tendance to stick after getting wet as other suggested oil and a coating of grease will help stop this but you need to get full travel on the pump shaft first. sounds to me that if the problem exist after disconnecting the cable from the contriols and you have the pump shaft moving freely you need to back off the idel set screw until you get the correct idle rpm.The idle set screw is not part of the pump so you will not be adjusting pump settings so don't worry about backing it off. If after you have the idle screw backed off recheck that you have full travel of the injector pump shaft. If after you do this and confirm it is not the lingage on the engine check you cables may be time for a new throttle cable or something in the control box haas a problem but you need elimanate the possible componets to diganose correctly. Good luck and let us know how you make out !
It seems to be loosening itself with movement. I have not taken any more time to get down below. The jet crash in Virginia Beach got me called in on a day off, and it's been my main focus since. I took the boat for a spin on April 1 and idle is around 1250 currently. I'll spray it with PB blaster next chance I get before I do anything drastic. I will actually verify I'm on the stop screw with a feeler gauge before I begin to adjust it up or down. None of this is all that easy because it requires some acrobatics to access these levers with the engine installed backwards.
On my 2GM the idle adjustment screw works only if the engine is in neuteal, It comes
off the stop when placed in gear,and can no longer be adjusted.
What happens when you drop it into gear?
off the stop when placed in gear,and can no longer be adjusted.
What happens when you drop it into gear?
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