912 ULS first start and checking the oil circuit

by Griffith Jones in 912 / 914 Technical Questions 8 years ago

I'm about to do my first engine run.
Item 25 on the "1st START checklist" here says to measure the mean crankcase pressure as per Install Manual 79-00-00 sec 1.3, essentially using a "home-made" pressure monitoring system. I can't find any references on this or other websites to builders doing this routinely. Does this need to be done following every first start? Or just if there is a problem?
If it does need to be done, what is the range needed on your pressure gauge?
Many thanks
Griff

Re: 912 ULS first start and checking the oil circuit

by Roger Lee » 8 years ago

Roger Lee

126 5.14k 4.58k

Hi Griff,

I believe the huge majority just start the engine. I'm always worried about a good solid purge so I do it twice and I do it a little longer than maybe needed. I do a good purge then take a couple of minutes then do it again. Then check the lifters. If everything is okay then start the engine. Make sure you have oil pressure right away. If you were doing a good purge you could have turned on the power and seen oil pressure on the panel. I usually see around 50 psi. I have never had soft lifters or a bad purge.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: 912 ULS first start and checking the oil circuit

by Griffith Jones » 8 years ago

Griffith Jones

2 1 0

Thanks Roger.
I had read a previous post of yours suggesting doing a few purges before first start and was already planning that. I didn't realize you could check the lifters before you had run the engine though.
Do you also re-check again them after the first run up reaches normal engine operating temperatures?
Many thanks again,
Griff

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Re: 912 ULS first start and checking the oil circuit

by Roger Lee » 8 years ago

Roger Lee

126 5.14k 4.58k

Watch this video:

http://www.rotax-owner.com/en/videos-topmenu/expanded-video-instructions/33-exp-si-912-01813

You pull the valve covers off and check for soft lifters. You just usually do it after the purge and before the start. You won't need to do it again if all is okay which it should be.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: Griffith Jones

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Re: 912 ULS first start and checking the oil circuit

by Bill Hertzel » 8 years ago

Bill Hertzel

13 1.95k 7.96k

I think this thread went sideways. ???

The question is about CrankCase Pressure, Not Oil Pressure.

I'm about to do my first engine run.... says to measure the Mean Crankcase Pressure as per Install Manual 79-00-00 sec 1.3, essentially using a "home-made" pressure monitoring system. ... Does this need to be done following every first start?... what is the range needed for your pressure gauge?...

This is a test done for the first start of a new installation in a new design.
As the designer of the airframe, you will need to verify that your Vent lines from the crankcase to the Oil Tank And from the Oil tank to the atmosphere are not restricting the ventilation of the Crankcase.

If you are installing an engine in a design "Where No Engine has Gone Before", The test is mandatory.
If you are building a known design from a Kit or Plans and have not modified the design, the test is optional if you trust the designer.

The crankcase pressure, as measured from the Magnetic Plug or Locking Screw ports, should not display more than 6.5psi, so a 10-15psi gauge should suffice.

Use a liquid dampened gauge as the pressure will be pulsing wildly with each piston stroke and oil gurgling through the vent lines.
This is the reason it is quoted as Mean (Average) Crankcase Pressure.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

Thank you said by: Matia F

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912 ULS first start and checking the oil circuit

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