'68 12F RPM woes

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Onfoot

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Hi guys. It's been a while. Hanna (my '68 12F grader) has done yeoman's service over the summer maintaining my 2km driveway. Snow has now arrived and yesterday was to be our first plow of the season. She started just fine and seemed to be running perfectly. But when I applied the throttle, the rpms would only slightly go up--barely past idle. I have posted on YouTube a video of my playing with the governor and you can hear what was going on. Here is the link: Hanna Governor. Needless to say, I did not get any plowing done.

Would welcome advice. The fuel filters were changed this time last year and have less than 100 hrs. Fuel is fresh with conditioner. All cylinders seem to be firing. I was thinking to change the filters, just in case. But have no idea about the governor or why it would suddenly not be working properly.

Thanks as always to the helpful collection of wisdom in this community!

Barrett

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Thu, Nov 3, 2022 11:04 PM

wimmera farmer

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Are you getting oil pressure. Rpm is limited untill oil pressure comes into operating range on our grader. Not sure how it works as I have never had any reason to study it.
cheersWF

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Fri, Nov 4, 2022 4:02 AM

Old Magnet

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Reply to wimmera farmer:

Are you getting oil pressure. Rpm is limited untill oil pressure comes into operating range on our grader. Not sure how it works as I have never had any reason to study it.
cheersWF

Agreed,does seem like your up against the speed limiter stop. Early versions of scroll pump had that feature. The speed limiter plunger resides on the back side of the governor behind a plug. Limits engine speed until operating oil pressure is obtained. I have never seen a spec on what minimum operating pressure requirement is to retract the plunger.
Might need to change to a winter blend cold weather viscosity oil or you may have other lubrication problems.
I suppose it is possible for the plunger to stick but I have not heard of or seen that happen.
Items 1, 2, 19, 18
[attachment=69378]Speed Limiter.jpg[/attachment]

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Fri, Nov 4, 2022 5:14 AM

Onfoot

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Reply to wimmera farmer:

Are you getting oil pressure. Rpm is limited untill oil pressure comes into operating range on our grader. Not sure how it works as I have never had any reason to study it.
cheersWF

Thank you, Old Magnet and WF. Will check out oil pressure tomorrow. Useful advice, as always!

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Fri, Nov 4, 2022 9:52 AM

Onfoot

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Reply to Onfoot:

Thank you, Old Magnet and WF. Will check out oil pressure tomorrow. Useful advice, as always!

In the way of an update... Thank you again to Old Magnet and Wimmera Farmer. It was indeed an oil-related issue, affecting the speed limiter. It was a stupid rookie oversight. The oil level was just at the 'add' line, which apparently resulted in preventing oil pressure from reaching necessary level. I brought the oil up to 'full' and everything worked like a charm. Note to self: ALWAYS check oil level. [img]/media/kunena/emoticons/doh.gif[/img]

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Sun, Nov 6, 2022 8:25 AM

Deas Plant.

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Reply to Onfoot:

In the way of an update... Thank you again to Old Magnet and Wimmera Farmer. It was indeed an oil-related issue, affecting the speed limiter. It was a stupid rookie oversight. The oil level was just at the 'add' line, which apparently resulted in preventing oil pressure from reaching necessary level. I brought the oil up to 'full' and everything worked like a charm. Note to self: ALWAYS check oil level. [img]/media/kunena/emoticons/doh.gif[/img]

Hi, onfoot.
We had a similar problem a few months back in the rear engine of a Cat 637D scraper although for a different reason. The engine and the injector pump had been rebuilt less than 400 hours previous but the engine had started running rough so we took the injector pump off to have it rechecked and reset. Turned out that the oil galleries in the pump were drier than a little wooden god.

To the best of my limited knowledge, there is only about one way that can happen in that motor - if the engine oil pump fails. So that scraper is sitting waiting for a decision on whether to rebuild the engine or dispose of the scraper.as we don't have much work left for it but it would look good at the Memorial Day Weekend show here on the ranch.

Just my 0.02.

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Sun, Nov 6, 2022 7:35 PM

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