Priming the oil pump through the relief valve?

[Guest]

Re: Priming the oil pump through the relief valve?

It should have a very small hole, moving oil through that small hole may cause excessive delay compressing air in the line.

However if within a few seconds after the oil pressure comes up at the initial start up we were to turn the engine off and notice how long after the prop stopped that it took the gauge reading to go to zero; then we would know how much delay is caused by the compression of air in the line.

[Guest]

Re: Priming the oil pump through the relief valve?

It should have a very small hole, moving oil through that small hole may cause excessive delay compressing air in the line.

However if within a few seconds after the oil pressure comes up at the initial start up we were to turn the engine off and notice how long after the prop stopped that it took the gauge reading to go to zero; then we would know how much delay is caused by the compression of air in the line.

[Hank Jarrett]

Re: Priming the oil pump through the relief valve?

Wow, looking at the photos and remembering the last rebuild I did has me scratching my head. Priming through the pressure reg valve hole should have NO effect. What has me confused is that every time I do it, I get oil pressure!
Got to be careful of perceived cause and effect! Sometimes it isn't what we think. Rain storms are NOT caused by wet sidewalks! Are we sure there isn't a passage from the gear cavity to the pressure relief valve cavity? I haven't got a rear case to look, but that is how I thought it would work originally. A passage that was covered with the plunger in one position and open in the other. With the plunger out, the oil would drain into the cavity. No passage, no oil. I'm confused as to why it works.

Hank

[Garry Crookham]

Re: Priming the oil pump through the relief valve?

Priming through the pressure reg valve hole should have NO effect. What has me confused is that every time I do it, I get oil pressure!
Hank

Priming thru the o/p relief valve hole will work, it just takes a lot of oil due to the long path to the oil pump. Also, if the engine has merely lost it's prime and hasn't been sitting for a long time there will be some residual oil in the passages which will be forced into the pump as the oil is pumped thru the hole. There is no direct path in the accessory case from the relief valve cavity to the oil pump. I'll try to take a couple of pictures of that area of the case when I have time, but these guys have priority:

[mikeg]

Re: Priming the oil pump through the relief valve?

Continental A65 oil pumps work just fine for years IF the clearances are correct to start with. I had problem and found that the gears had worn journals and worn bores in the magnesium rear cover. I lapped the grooves out of the cover and put new Continental gears in a good aluminum rear cover and have not had a bit of problems since (800+hours).
Mike
NC29804
NC27451

[Guest]

Re: Priming the oil pump through the relief valve?

Hi Garry and all,

It will take a lot of oil as you say and some pressure as well.

That's because the path is up hill to the front of the engine and to get oil up the hill and back to the pump you have to contend with oil losses from the main bearings, can bearings and rod bearings.

My point is that simply removing the plunger and squirting an oil can in there is not going to do it.

BTW this is an interesting discussion.

No intention to insult or offend anyone but I suspect that the discussion is ripe with misunderstanding, lack of knowledge, mistaken cause and effect, poorly defined terms, sloppy language, multiple scenarios that are being confused as one and all that kind of stuff. Well for not intending to offend I probably covered all of us!

But the bottom line for me is that you guys that are having these problems you should consider whether an engine that can't self start its own oil pressure is in a condition for safe operation. That is part of the definition of airworthy. I see engines that sit for months and then start up with good oil pressure, no messing around, that's how it is supposed to be. I don't think that an engine that has to have its oil system doctored up to get initial oil pressure is in a condition for safe operation and would not pass it for annual.

Regardless of all that please consider getting it fixed. A $800 oil pump will be cheaper than a stopped engine and the results it can bring.

I say $800 because ; gears/kit- $400, shop work on cavity $325, misc- $75

Dave

[Edwin Otha]

Re: Priming the oil pump through the relief valve?

Most of the problem comes from the shaft holes for the gears. It's a lot easier to pull air than oil. As discussed, the lifting of the tail allows the oil to flow into the pump from the screen area. Now this only works on the 65, the screen is lower on the 85's.
This egg shaping of the holes is from taking off on cold oil, it forces the gears apart and elongates the shaft bores. The pump cavity can be pretty bad before it causes any problem. This is the coasting side of the pump and doesn't effect indicated presure too much.
EO

[Guest]

Re: Priming the oil pump through the relief valve?

I found a shop that will bush the bores in the acc. case for the gear shaft for about $275. a new plate on the inside will help too and is inexpensive.

[Garry Crookham]

Re: Priming the oil pump through the relief valve?

Now this only works on the 65, the screen is lower on the 85's.

EO

The A65-8 and the C85-8 use the same accessory case. The C85-12 accessory case is totally different and yes the screen is lower and in a different location, as is the pressure relief valve.

[Hank Jarrett]

Re: Priming the oil pump through the relief valve?

Nothing so nice as a day at the Beech. ;-)

Hank

Priming thru the o/p relief valve hole will work, it just takes a lot of oil due to the long path to the oil pump. Also, if the engine has merely lost it's prime and hasn't been sitting for a long time there will be some residual oil in the passages which will be forced into the pump as the oil is pumped thru the hole. There is no direct path in the accessory case from the relief valve cavity to the oil pump. I'll try to take a couple of pictures of that area of the case when I have time, but these guys have priority:

[Hank Jarrett]

Re: Priming the oil pump through the relief valve?

"The discussion is ripe with misunderstanding, lack of knowledge, mistaken cause and effect, poorly defined terms, sloppy language, multiple scenarios that are being confused as one and all that kind of stuff. Well for not intending to offend I probably covered all of us!"

Oh my gosh! We have turned into GOVERNMENT!

Hank

[LostnSpace]

Re: Priming the oil pump through the relief valve?

Hank, that towbot in the picture is the cats meow for moving a plane, I stopped in at St. Simmons Island, to pick up a Pilatus pilot that was delivering it to the owner, when he stopped it outside his hangar, the owner picked up his remote control, and drove it under the nose wheel, picked it up, and as he motored it into the hangar ( along with his PC-7 Pilatus), he walked around behind the plane to watch how it was fitting in, all while controlling it with his little remote, very neat, always fun to see how the "other side" lives, gary

[Guest]

Re: Priming the oil pump through the relief valve?

"the discussion is ripe with misunderstanding, lack of knowledge, mistaken cause and effect, poorly defined terms, sloppy language, multiple scenarios that are being confused as one and all that kind of stuff. Well for not intending to offend i probably covered all of us!"

oh my gosh! We have turned into government!

Hank

lol!

[Garry Crookham]

Re: Priming the oil pump through the relief valve?

Hank, that towbot in the picture is the cats meow for moving a plane

Yes, the towbot has made moving airplanes much easier for us. Trying to move a 421 or Navajo around used to be a back breaking job but now it's a pleasure. At Oshkosh last week a towbot was being used to move a B-25!

[Edwin Otha]

Re: Priming the oil pump through the relief valve?

Correct about the -8 engines, same back plate. There just isn't many in use. Generally people will use the -12 engines and block off the un-needed acc. locations.
EO