Fuel Limiter Screw Adjustment?

[ScottySailor]

Hey all doing some work on my Yanmar 2gmf and I stupidly took apart the fuel limiter screw whoops!!
Anyway the manual says it is set at the factory and only manufacturer should set it!!
So I need to adjust it to the correct specs any tips/advice please??
Help me OB1 your my only hope..

 

[RoyS]

Is this the device that limits maximum engine RPM? If so, purchase an optical RPM meter (not overly expensive), find your published maximum engine RPM in your manual. Warm up engine in neutral. Slowly approach maximum RPM as displayed on meter and set the screw to hold that maximum RPM. Optical RPM Meter is good for checking your boat tachometer accuracy, also.

 

[NYSail]

As a start point, hopefully you didn't clean the screw ..... maybe there is some tell-tale aging on the portion not screwed in that can get you close.

Good Luck!

 

[kloudie1]

To set .. Not a job for the weak hearted! Hope this points ya in the right direction..

 

[kloudie1]

Here are the levers referenced in the drawing..

 

[RoyS]

Oh, that screw. I thought you meant the sealed maximum throttle screw. I have no experience or opinion on the fuel limiter screw.

 

[ScottySailor]

Oh, that screw. I thought you meant the sealed maximum throttle screw. I have no experience or opinion on the fuel limiter screw.

I think they’re the same thing?

 

[ScottySailor]

To set .. Not a job for the weak hearted! Hope this points ya in the right direction..

I already had to take off the timing cover to replace the gasket which was leaking and I removed and reinstalled the injection pump which is why I was fiddling around with the Limiter screw so I could get the pin on the injector pump to go into the slot for the governor lever…
Anyway I read through both the PDFs very helpful but I’m still not a hundred percent sure what’s going on if you could explain in layman’s terms that would be helpful.?
Also couldn’t I screw that screw in a little bit then start the engine run it at maximum throttle which wouldn’t go to maximum because I screwed the screw in and then back off till it hits 3500 rpm?

 

[kloudie1]

I am not an expert on that adjustment by any means.. I think that the injection limiter screw is an "absolute maximum" mechanical stop for the injection pump volume control rack.. I think that the "max unloaded speed screw" sets how much tension the regulator spring puts on the governor from the hand speed-control lever. There are times when a lot of torque from the engine is needed at lower than maximum RPM.. The injection limiter screw sets the max that the rack can go to when called for FULL Power .. if you set the max no-load speed with the limiter screw, the rack will be constrained too much and the engine will not make "rated" horsepower.. If you haven't messed with the "No-Load max speed" you can do as you note.. that is raise the rpm via the hand control lever until it is at max then slowly screw in the injection limiter until the rpm just starts to reduce.. now, since that is too conserative a setting you might shut the engine down and back out the injection control shaft by a couple of turns then operate the boat and see if you can get to max loaded RPM going forward (assuming that your prop is about correct) A clue to the limiter shaft being set too "loose" would be more smoke than normal at startup..The limiter stops the rack at a max setting when the engine is shut down. Note that the "injection control shaft" is what is being set and not the little spring retainer screw..
If one were to attempt setting that way, start with the limiter shaft screwed in pretty far ..
Again I am not an expert here but the process above would be a logical way to get close.. Good luck..

 

[RoyS]

I think they’re the same thing?

Not the same. The sealed screw I was referring to is labeled “No-load maximum speed limiter” in this photo:

 

[ScottySailor]

I am not an expert on that adjustment by any means.. I think that the injection limiter screw is an "absolute maximum" mechanical stop for the injection pump volume control rack.. I think that the "max unloaded speed screw" sets how much tension the regulator spring puts on the governor from the hand speed-control lever. There are times when a lot of torque from the engine is needed at lower than maximum RPM.. The injection limiter screw sets the max that the rack can go to when called for FULL Power .. if you set the max no-load speed with the limiter screw, the rack will be constrained too much and the engine will not make "rated" horsepower.. If you haven't messed with the "No-Load max speed" you can do as you note.. that is raise the rpm via the hand control lever until it is at max then slowly screw in the injection limiter until the rpm just starts to reduce.. now, since that is too conserative a setting you might shut the engine down and back out the injection control shaft by a couple of turns then operate the boat and see if you can get to max loaded RPM going forward (assuming that your prop is about correct) A clue to the limiter shaft being set too "loose" would be more smoke than normal at startup..The limiter stops the rack at a max setting when the engine is shut down. Note that the "injection control shaft" is what is being set and not the little spring retainer screw..
If one were to attempt setting that way, start with the limiter shaft screwed in pretty far ..
Again I am not an expert here but the process above would be a logical way to get close.. Good luck..

Thanks I’ll take my time and try to work through it, there’s a yanmar authorized shop near the boat I’ll try bouncing it off them before I mess anything up. Lol

Not the same. The sealed screw I was referring to is labeled “No-load maximum speed limiter” in this photo:


Excellent thanks for clarifying I’ll look at that.

 

[ScottySailor]

Here are the levers referenced in the drawing..

Kloudie 1 need your guidance.
After assembly and starting up my engine races at full speed no matter what the throttle is set at. I have to cover the air intake and flip decompression levers for it to stop. It’s scary. Anyway I think it has something to do with adjusting the rack and levers and fuel limit screw.
I read your pdfs ten times lol. It’s sinking in but what does it mean to set governor lever 2 in free position?
Any other layman’s guidance would be appreciated I’m pretty mechanical but this one is tricky. Thanks . Pm if easier.

 

[Charles Erwin]

When you drop the pump back in place make sure the rack pin (the pin that sticks out horizontally from the rack) drops into the fork of the governor lever. Otherwise the motor is ungoverned and will "run away."

You can just barely see these parts engage each other through the inspection port - so use your finger to verify the pin engages the fork. Once that is done tighten down the four nuts that hold the pump in place.

Can send pictures if you want but look at Kloudie's last diagram. The fork is labeled 'Governor lever 2.'

Charles

 

[ScottySailor]

When you drop the pump back in place make sure the rack pin (the pin that sticks out horizontally from the rack) drops into the fork of the governor lever. Otherwise the motor is ungoverned and will "run away."

You can just barely see these parts engage each other through the inspection port - so use your finger to verify the pin engages the fork. Once that is done tighten down the four nuts that hold the pump in place.

Can send pictures if you want but look at Kloudie's last diagram. The fork is labeled 'Governor level 2.'

Charles

Thanks Charles. I verified it was in the right place looking in the inspection port with a flashlight and mirror.
I think originally I had the fuel limiter screw out of adjustment would that cause the same problem?

 

[Charles Erwin]

Doubtful. The limiter has no effect unless the throttle is full on maximum. At part throttle the limiter does nothing.

You had better double check.

Tip you can take the silencer and cover off the intake exposing the intake tube, then in case of a runaway you can use a tennis ball to strangle the thing. CO2 extinguisher pointed at the intake will kill it too. (Hope you don't need these tips.)

Charles

ps Did you try the fuel cut off?

 

[ScottySailor]

Doubtful. The limiter has no effect unless the throttle is full on maximum. At part throttle the limiter does nothing.

You had better double check.

Tip you can take the silencer and cover off the intake exposing the intake tube, then in case of a runaway you can use a tennis ball to strangle the thing. CO2 extinguisher pointed at the intake will kill it too. (Hope you don't need these tips.)

Charles

ps Did you try the fuel cut off?

Fuel cutoff has no effect.
To preface this whole thing I originally took Off the timing cover because it had a leak when I reassembled I didn’t see anything unusual???

 

[Charles Erwin]

Scotty

The entire throttle control system on this motor is dependent on the rack pin to lever 2 fork slot engagement. Accordingly -

The fuel cut off cannot work unless the pump rack pin is engaged in the lever 2 fork slot.

This motor will "run away" unless the rack pin is engaged in the lever 2 fork slot.

There is no throttle control unless the rack pin is engaged in the lever 2 fork slot.

I am not there. However - consider this. Of the three symptoms of mis-engagement you suffer from all three. That means there is a near 100% chance the fork slot did not engage the rack pin when you lowered the pump into place.

Remotely possible the throttle (called regulator) spring(s) positions were wrong but it is really hard to disturb these spring positions if all you did was simply remove the front cover to replace the perimeter seal.

Take the inspection cover off feel inside you will find the fork slot/pin is not right - probably the slot is rearward of the rack pin. Even better - take the cover off, aim your phone camera in there, and send a photo.

Charles

 

[ScottySailor]

Scotty

The entire throttle control system on this motor is dependent on the rack pin to lever 2 fork slot engagement. Accordingly -

The fuel cut off cannot work unless the pump rack pin is engaged in the lever 2 fork slot.

This motor will "run away" unless the rack pin is engaged in the lever 2 fork slot.

There is no throttle control unless the rack pin is engaged in the lever 2 fork slot.

I am not there. However - consider this. Of the three symptoms of mis-engagement you suffer from all three. That means there is a near 100% chance the fork slot did not engage the rack pin when you lowered the pump into place.

Remotely possible the throttle (called regulator) spring(s) positions were wrong but it is really hard to disturb these spring positions if all you did was simply remove the front cover to replace the perimeter seal.

Take the inspection cover off feel inside you will find the fork slot/pin is not right - probably the slot is rearward of the rack pin. Even better - take the cover off, aim your phone camera in there, and send a photo.

Charles

Charles, Looked in the inspection hole yesterday for an hour with a mirror and flashlight, the pin on the injector pump is definitely in the slot, when I push the throttle all the way max it hits the max rpm screw so that looks good, when I read the pdf's from above by Kloudie 1 I can see that the Injection limiter needs adjusted, I can't quite comprehend the directions , anyway everything inside the inspection port seems to be moving ok etc, I'll be back at the boat in 2 weeks so looking for ideas before I get back. Anything else that you think it could be?
thanks

 

[ScottySailor]

Conclusion.
Thanks to all who helped me with this.
The final problem was a defective fuel injection pump this was causing the engine runaway, I think when I originally tried to remove the timing cover (without fully reading the manual) I bent the pins inside the pump which on start up then gave the engine full fuel all the time.
I got the pump and injectors rebuilt and engine now purrs like a salty kitten.
A $1000 lesson learned. Lol
Thanks to all.

 

[jssailem]

A $1000 lesson learned.

That is why it is called a B.O.A.T....
Break Out Another Thousand.....