Precautions for starting an engine that has sat

There are some precautions to take when first starting an engine that has sat and not run for several years.  The information in this newsletter is for informational purposes only.  Always consult with an A&P or IA with any questions related to this topic.  The information within this newsletter is based on an aircraft that Flymall.org was brokering.  It had not been flown for several years and the engine had not been run for over a year and a half.  Flymall.org as well as several customers spoke with several shops and all agreed that the power-plant could be serviceable in its current state however everyone also agreed that the power-plant could also have too much internal damage from sitting and require a major overhaul.  The shops interviewed said that they have seen cases of both circumstances on aircraft after sitting similar amounts of time.

A total of 3 shops were consulted with regarding this particular aircraft.  And all 3 shops seem to share a common belief in a fairly similar procedure for starting the aircraft:

Pull the top spark plugs and borescope all 4 cylinders to see what they look like internally.  If the cylinders look acceptable, pre-oil the cylinders through the spark plug hole using Marvel Mystery Oil, WD-40, or similar.  Then hand-prop the engine several times to circulate the pre-oil.  One shop suggested allowing the pre-oil to sit overnight.

One shop recommended turning over the engine with the starter (fuel off or mixture lean) until oil pressure registers on the pressure gauge.  This further pre-oils the engine.

Start the engine and run for 5-7 minutes.  Stop the engine, conduct a full oil change, and see what metal, if any, is in the cut oil filter and oil screen.  If you do not find any metal, consider flying the plane for 5-6 hours, then conduct another oil change and look for metal again. If metal is found at any time in the process, it is likely that a top overhaul may be required or a major overhaul may be necessary due to rust scoring the moving components.

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