So I was going over the engine (yanmar 3gm30f) when I noticed two round holes on top of the fuel injection pump. The one you see in the picture and another diagonal to it obscured by the hose. Does anyone have an idea what these are ? I looked at a schematic of the pump in a parts catalog and there faintly appears small holes in these areas. I am puzzled
Hole in Fuel Pump
- Thread starter nveater
- Start date
If the engine is running properly, they are likely remnants of the manufacturing process. The molds used to cast metal parts are assembled and held together by guides which will leave holes in the parts when removed from the molds. These holes could have also been engineered into the part to provide attachment points to hold the parts in a finishing process. As a young and poor college student in Milwaukee I got a job at a foundry that casted cylinder heads for Harley Davidson motorcycles. Our section used to make and assemble the molds where the molten steel was later to be poured into. Seen many holes in finished parts that were only intended to be used in later steps of the manufacturing process. Did not stay there long as I realized the silica sands used in making the molds was so fine that it got inside my watch and did not take much thought to realize that they would also be collecting in the lungs.
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Those are the tops of the holes for locating "spring pins" that precisely locate the HP pump into the gearcase. If you pull the HP pump, you'll see the little split pins driven into the gearcase. Not to worry!
EDIT: As Benny noted, when the cover is cast, those holes are rough and smaller than necessary. A finishing step is to drill those holes from the underside to finished size, but not all the way through the cover; what ya are seeing is the end of that rough, too-small hole . If you were to look at the underside, you'd see a fine finished hole probably 3/4 of the way through the cover. Don't take it off to confirm !
EDIT: If you pull up the Gear Housing parts, you'll see the little pins on the pump mounting surface. They serve to locate the timing shims as well..
EDIT: As Benny noted, when the cover is cast, those holes are rough and smaller than necessary. A finishing step is to drill those holes from the underside to finished size, but not all the way through the cover; what ya are seeing is the end of that rough, too-small hole . If you were to look at the underside, you'd see a fine finished hole probably 3/4 of the way through the cover. Don't take it off to confirm !
EDIT: If you pull up the Gear Housing parts, you'll see the little pins on the pump mounting surface. They serve to locate the timing shims as well..
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Agree....
when inspecting and doing maintenance, there are a few basic rules to follow.... and the farther you are from the repair shop, the more important they become.... the first two rules are,
1... if it isnt broke, dont try to fix it. 2..... and if it isnt fixable, dont break it....
If there's no fuel squirting out, I wouldn't worry about them. One of those mysteries we don't need the answer to.