Priming the oil pump through the relief valve?

[Guest]

Re: Priming the oil pump through the relief valve?

Stumpy,

Does your oil pressure drop after the engine warms up?

Said a different way; what oil pressure do you have on start up and what oil pressure do you have after it is warmed up?

Just curious.

Dave

[senior]

Re: Priming the oil pump through the relief valve?

Do these engines that have oil pump priming problems (ie. start up oil pressure problems) also have a problem with low oil pressure after the oil comes up to temperature?

I believe what you highlighted in red is the answer.
As far as oil pressure, what is low oil pressure?
Is an engine that runs 30lbs but drops to 10-15lbs at idle low pressure?
My inclination is yes it may be slightly low pressure but not necessarily a problem, after all some of these engines are 70yrs old

Also engines that continuously loose pressure I would say do have a problem, but if an engine sits a month or two or three before it looses prime...not so much.

Perhaps a definition of "on her nose" by original poster could be clarified,
I took it as simply raising the tail.

[Guest]

Re: Priming the oil pump through the relief valve?

Senior,

Said a different way; what oil pressure do you have on start up and what oil pressure do you have after it is warmed up?

Dave

[flyguy]

Re: Priming the oil pump through the relief valve?

Dave,
The first piece of junk Tcraft that I owned worked like this: After a week of inactivity I would fire it up and have no oil pressure. I would go back and, with the engine running, lift the tail as high as I could and the oil pressures would come up. When it was running it did in fact have low oil pressure. Very low when at idle.
Sometimes it would be OK for one week of not being started. Outside temperature?

DC

[astjp2]

Re: Priming the oil pump through the relief valve?

So it wasn't a junk airplane, it was a junk accessory case on a continental engine....something easily fixed with the right parts. tim

Dave,
The first piece of junk Tcraft that I owned worked like this: After a week of inactivity I would fire it up and have no oil pressure. I would go back and, with the engine running, lift the tail as high as I could and the oil pressures would come up. When it was running it did in fact have low oil pressure. Very low when at idle.
Sometimes it would be OK for one week of not being started. Outside temperature?

DC

[flyguy]

Re: Priming the oil pump through the relief valve?

No, as per usual when you jump on my case, you have NO idea what you are talking about.

That plane, in addition to being in generally god-awful shape, had about a half dozen items that could have killed me. Fortunately I found most of them before that happened. It was still a piece of junk overall.

Furthermore if you can only come on with caustic smart-assed remarks when you reply to something here, you really should just put a lid on it.

Darryl

[astjp2]

Re: Priming the oil pump through the relief valve?

Darryl, sorry to ruffle your feathers but you never really said why the airplane was junk...something like cracked spars, ratty fabric, brakes that would not hold, leaky fuel system would have made it clear that there were other problems with the airplane than just the oil pump. It sounded like the airplanes major problem was the oil pressure and that is why you classified it that way. Tim

[Stumpy]

Re: Priming the oil pump through the relief valve?

Senior,
Sorry, I shoulda clarified better in the OP. Double-entendre...meant that it was running an A-65 AND the tail was up...but not THAT far up. ;-)

Dave,
At start-up cold she's up around 35 lbs. When oil temps are 180 I'm running 28+/- at cruise, idle down around 10, sometimes drops below a hair. She's been right on those numbers since I've had her. Been running aeroshell 100 but went with 100-plus this change... A-75 with a 70-40 sensenich woody.

Need to pull the relief and look it over/give it a good cleaning. Probably put a new spring in too just because...because I have one and the one currently installed is old and tired, like me.

[flybikefarm]

Re: Priming the oil pump through the relief valve?

Lucas oil treatment.

[Garry Crookham]

Re: Priming the oil pump through the relief valve?

It might help the discussion if there were some pictures posted of the accessory case, oil pump etc so I'll try to do just that:

first picture, the accessory case



second picture, inside view of accessory case



picture of oil pump gears and oil pickup tube



more of the oil pump area



rear of the crankcase



As the pictures show, if you prime the pump via the pressure relief valve opening the oil has to travel a long way to reach the pump, but priming thru the oil screen (actually through the fitting in the back of the screen after removing the oil temp bulb, is a very short distance.

[Garry Crookham]

Re: Priming the oil pump through the relief valve?

This should have been the second picture in the above series showing the screen and pressure relief valve as removed from the accessory case

[woodmw]

Re: Priming the oil pump through the relief valve?

Garry,

Great post. These pictures tell many thousands of words. After removing my instruments and panel to replace the fuselage fuel tank, I had no oil pressure on first start. The change started as a repair and then went to a replacement. That, along with other interior work had kept the plane down for quite a few months. I pumped some oil through the hose forward of the firewall, and the hard line from firewall to OP gauge, making quite a mess, but still no pressure. I tried to pump about a pint of oil in the oil pressure pickoff just forward of the oil pressure relief valve to prime. Pumped more oil in hose/tube to gauge, making another mess, and tried turning prop with all spark plugs removed. Gave up on turning prop by hand and just started engine. Ran around to cockpit and OP was 35+. Just like normal. I'm thinking, after looking at pictures and learning about our little engines, that squirting oil in the engine didnot prime oil pump, I just finally got air out of oil pressure line.

Again, thanks for the pictures.

[Guest]

Re: Priming the oil pump through the relief valve?

Garry,

Great post. These pictures tell many thousands of words. After removing my instruments and panel to replace the fuselage fuel tank, I had no oil pressure on first start. The change started as a repair and then went to a replacement. That, along with other interior work had kept the plane down for quite a few months. I pumped some oil through the hose forward of the firewall, and the hard line from firewall to OP gauge, making quite a mess, but still no pressure. I tried to pump about a pint of oil in the oil pressure pickoff just forward of the oil pressure relief valve to prime. Pumped more oil in hose/tube to gauge, making another mess, and tried turning prop with all spark plugs removed. Gave up on turning prop by hand and just started engine. Ran around to cockpit and OP was 35+. Just like normal. I'm thinking, after looking at pictures and learning about our little engines, that squirting oil in the engine didnot prime oil pump, I just finally got air out of oil pressure line.

Again, thanks for the pictures.

Thanks for the info Mike.

I have been wondering if the delay seeing the pressure reading was causing some of this concern.

From what you said I can see that it is possible.

Dave

[astjp2]

Re: Priming the oil pump through the relief valve?

Once the gauge line is pressurized, it will not have much of a delay, maybe a few seconds at the most. Oil will compress the air to 30 psi in the gauge line, this may not be as accurate as all oil but its close to a true reading. THe compressibility in a 1/8" oil line is not much volume compared to what the pump puts out. How many of us have put in a new plug or spring? I was wondering if it may be part of my problem with low pressure at cruise vs potential for loss of prime from the bypass side. Tim

[cvavon]

Re: Priming the oil pump through the relief valve?

Maybe i missed it but has any one took a look at the very small hole that is a restricter in the oil line to slow oil loss if the line has broken for a blockage.