Not being a "mechanic", I need some advice.  I just finished installing a freshly major overhauled O200A on my 750.  I filled the oil tank.  When I checked for oil pressure before performing the first start, no oil pressure was indicated.  I know that my electric sensing oil pressure indicator works. 

Before I drop the kidney tank - messy job - and check the pickup tube, is there any other check that I might perform first?

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Don't be convinced that your electric OP Gauge works. I learned from experience that an analog gauge is a must. You can get a really small one that could fit anywhere on your panel.

Prior to starting did you run the pump to initialize pressure?

I even filled the oil filter.  I tried to "pre-lube" before the actual attempt to start engine.  I used a procedure similar to the Lycoming procedure for newly overhauled engines to pre-lube the engine before normal start.  Should be able to get an indication of some oil pressure.  I did on my other engine in a similar fashion. Electric oil pressure gauge and sensor worked as it should during that test.  That engine needed overhaul and I changed from the C90 to this newly overhauled 0200A.  Must be an air pocket somewhere or a blockage.  Not looking forward to dropping the oil tank, but I probably have to start there....unless someone has another idea.

I am confused, isn't the oil pump engine driven.  If so you won't see oil pressure until you start your engine.


Yes, it is engine driven.  But, after overhauls, it is recommended to "pre-oil" the engine by turning over the engine without starting to remove air pockets and "prime the lines".  Oil pressure should be indicated during the process.  See Lycoming's Service Instruction at this link:

I've been looking for something on the Continentals on this but haven't found anything yet.


That makes sense now.  When resurrecting an old engine we used a pressurized oil supply to pre-lube the engine since it had been sitting for 7 years prior to starting.   I would check the easy stuff first, an analog guage is a must have for this problem.

I agree...I'll rig up a direct reading gage to double check first before taking more drastic action.

i use a preoiler bottle on new or rebuit  continentals before first start, connect to oil pressure port, turn on bottle and pressure is in system. disconnect re attach pressure line and start.

as an example Allstar Performance Oil Pressure Primer Tank ALL10535 :...

Thanks, Christopher for the link.  I was wondering if anyone used these on aircraft engines.   One of the local A&Ps might have one I can borrow.  If I have to, I'll buy just takes so long to get stuff to Alaska.

Persistance prevails !!  I spoke with the overhauler and we discussed the problem.  He mentioned that he used makeup oil to prelude the oil pump gears and other components.  A local A&P advised me that he uses a thicker lube when assembling an overhauled engine that will adhere better to the metal parts.  What he suspected is that the makeup oil viscosity was too light and the lube drained away such that air pockets reappeared to prevent proper pump ops and an indication of oil pressure.  After pushing oil into every opening again plus the "clean" exhaust from a vacuum cleaner into the oil filler neck, the  galleys filled with oil and I got an indication of pressure this time.  Problem solved and thanks to all for your comments and suggestions.     Bill

Hi Bill:

Can we safely assume you are using mineral oil for the break-in as recommended for overhauls and new 0-200 engines? 

I read your input with interest as I ran across the same issue when I first fired up my newly overhauls 0-200.  In this case we removed the external filter and injected mineral oil into both oil ports while being sure the filer had plenty of oil in it.  Problem resolved on propping and startup.  

John Minatelli

Hi John,

Mineral oil absolutely.  As I mentioned in earlier post, the output from a vacuum cleaner into the oil filler tube provided the necessary pressure to move the oil to the oil pump and remove those air traps.  

The O-200 can be pre oiled by pulling the brass plug from the case and deliver 100w straight mineral at 40 psi. Once primed it will register on the gauge and allow you to validate the pressure gauge. It never takes more than 3 quarts.


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