Can't get oil pressure

Priming the system for first start.

Pushed one quart through the oil pressure sensor line to fill galleries.
Confirmed cooler and sensor are plumbed correctly per Dan H diagrams .
Oil comes out pressure sensor port by hand and starter cranking ( plugs out).
Installed mechanical gauge known to work.
No pressure cranking by hand or starter
Concerned about a lot of cranking without pressure. Engine was inverted for cam oil before install, but what to try now ?? All suggestions appreciated.

Larry,
Little confused. You said you have oil coming out the pressure port during cranking but no pressure on the mechanical gauge? I assume you mean the mechanical gauge hooked up to that pressure port that you see oil coming out of during cranking?

You probably did this but it's worth asking: are there at least a few qts of oil in the sump?

Thanks kahuna

Yes kahuna, the Fligtlines flex hose going to the sensor will drip oil when the engine is cranked by hand or with starter. When the mechanical gauge that is known to work is connected to the line, pressure does not register cranking by hand or with starter. Conclusion is the oil must have low resistance path somewhere.

Past threads have commented to fill the cooler, but when cold, the vernatherm should shunt oil direct to the galleries ? Thanks for your response.

When I built my engine in 2006 we cranked it by hand and starter about a million revolutions (slight exaggeration) and never got an oil pressure reading. I gave up and started the engine and had oil pressure immediately after start up.

Thanks Russ

It appears your experience is where I am at. There were 5 qts in the sump plus the 1qt. I pushed through the oil pressure sensor line. If I don't get other ideas to try, I will just start it with the mechanical gauge and hope. I wanted to avoid troubleshooting more than necessary at the airport because it is starting to cool off in Indiana.

Larry,
There is a plug in the oil pick-up line of the case right where the sump joins up in the back. You leave the plug in for a bolt-on, sump centered pick-up and take the plug out for a sump with a built in sump pick-up. Accidentally leaving the plug in when switching to a sump with the built in pick-up doesn't work too well. Don't ask me how I know. You might want to double check that.
Alan
RV-4

Oil Pressure

I never prime the oil line or fill the cooler. Just pull one set of spark plugs, hook up the oil pressure line and crank with starter. No more than a minute or so at a time to avoid overheating the starter. Pressure usually comes up within 30 seconds or so.
What is the history of the engine. If it is built by someone who is not building engines all the time it would be very easy to leave out one of the pipe plugs inside of the accessory case. There is also a pipe plug in the oil pump housing which IIRC is only on some of the newer PMA pump housings.
Would you email me regarding Parakeets [email protected]

I have had this happen before. The engine just wouldn't prime. Allen Barrett told me that when that happens, he pulls the accessory case and the oil pump and packs the pump full of Vaseline. That created more suction that air and it primed right away with that trick.

Oil Pump

One recent recommendation, can't remember the source, is to lube the pump gears and cavity with lubriplate. I did that and had near instant oil pressure with the starter, no filling the oil line or cooler. The recommendation may very well have come from Alan, I attended an engine assembly forum that he did years ago.

Pre Oil

Apples and Oranges but Rare Bear gets pre oiled before every engine start. Electric pump in the left wheel well, I think it has a quick disconnect and is removed after each start.

Pre Oil

When you exhaust all other possibilities other than taking the engine apart, I would construct a simple pre oiler from a cheap electric pump and pre oil via a port as close as possible above the oil pump. Then quickly put everything back together and crank with the starter.

Pump spears to be primed

Thanks for all the suggestions. The pump appears to be functioning because oil comes out the pressure gauge port when you crank it. At this point, Russ's experience, start it, is the logical next step ?????

Larry is your gauge, either mechanical or in cockpit, capable of reading psi less than 10? During cranking, with the plugs out of course, you should see the pressure rise off zero to a # greater than 5. That is your ticket press on.

Thanks Kahua

Yes, the mechanical gauge worked on an 0200 recently and an air gun blowing in to hole will register 10-15 psi.

Larry DeCamp said:

Yes, the mechanical gauge worked on an 0200 recently and an air gun blowing in to hole will register 10-15 psi.

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I think Kahuna suggesting your gauge needs to be able to read pressures less then 10 psi more like 5 psi, if your gauge won't read that low you might have 5 psi and it reads 0.

Thanks Russ

Yes, prior experience with antiques suggest if oil comes out the port the pump is primed ! My gauge may not be sensitive to 5 psi. All points well taken, I am going to Fire It Up.

Larry DeCamp said:

Yes, prior experience with antiques suggest if oil comes out the port the pump is primed ! My gauge may not be sensitive to 5 psi. All points well taken, I am going to Fire It Up.

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I think you are on the right track. let us know how it goes.

Larry DeCamp said:

Yes, prior experience with antiques suggest if oil comes out the port the pump is primed ! My gauge may not be sensitive to 5 psi. All points well taken, I am going to Fire It Up.

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Well, I would keep spinning until oil pressure was up, but it would run for 5 minutes at 1000 rpm without oil pressure or damage, but not longer.

In the diesel engine lab, to test bearings, an engine is run until hot, the oil is drained, the pan removed, the oil pump removed, left to drip overnight, then started at idle and run until it seizes. With a good modern oil, and bearings, it can run for 30 min to hours. Just amazing. Remember engine has 17.5 Cr and it has full compression force as there is no throttle valve. It has much better bearings than a Lyc. 5 min and you should be fine w/o pressure - ONCE.

Let us know how the first start goes!

If the engine was assembled with assembly lube like stp etc then you do have a couple of minutes grace, but you should have pressure in just a few seconds after startup. If not something is very wrong. I had that with a c90. There were bolt holes on the cam for a vacuum pump gear but I was not running vacuum so those holes were supposed to be filled with short bolts. But they weren't so the oil went up the left gallery and instead of flowing through the groove in the cam boss into the right gallery it just came out through the 6 open holes back into the sump! We probably put 90 seconds on the engine trouble shooting before we figured it out. The builder had to tear it down and fix it. When he had it open he found there was no damage to the internals from that short period of running.

How long are you spinning it with the starter? Can take a little bit to build pressure. Assembly lube prevents damage while cranking, so don't be shy.

GOT OIL PRESSURE !!!

Thanks to all for the encouragement.

Russ calmed my fears and I was prepared to start it. ColoRv caused me to think about how little I had cranked it. So I cranked until it stopped burping air, about a half cup and I got 30 PSI instantly. Thanks again guys, tomorrow we light the fires with tail tied DOWN WELL !

Larry DeCamp said:

Thanks to all for the encouragement.

Russ calmed my fears and I was prepared to start it. ColoRv caused me to think about how little I had cranked it. So I cranked until it stopped burping air, about a half cup and I got 30 PSI instantly. Thanks again guys, tomorrow we light the fires with tail tied DOWN WELL !

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Cool, have fun!!!

Very good Larry!
Tom

Jesse said:

I have had this happen before. The engine just wouldn't prime. Allen Barrett told me that when that happens, he pulls the accessory case and the oil pump and packs the pump full of Vaseline. That created more suction that air and it primed right away with that trick.

Click to expand...

Most mechanics will be generous with assembly lube (essentially a light grease that breaks down and mixes with the oil after startup) in the oil pump upon assembly to insure an initial prime (based upon my auto experience). You should be able to get a measurable pressure reading with just starter cranking (I got a few PSI after 30-60 seconds and 20 PSI after about 2 min. - No priming other than pouring 6 quarts in the sump) . While it is quite possible that it will prime once you hit a higher RPM, there is also a chance that there is a problem and you won't get pressure after start up. How long you can run without pressure is to some degree based upon the lubes used during assembly. If they just coated parts with regular oil (not recommended), you don't have a great amount of time before you start getting wear in your bearings/journals. Proper lubes will give you more time for the oil to flow. Be advised, unlike auto rebuilds, Lycoming recommends using engine oil with STP for coating most parts and then requires an oil priming procedure prior to startup. I have no idea what the industry practice is. I followed my experience and used assembly lube.

I suspect you don't know what is inside and I would investigate a bit more before proceeding. Because you poured oil in the sensor hose, I am not sure how confident I would be in oil dribbling out during cranking. I would keep at it until I could observe flow somewhere. You could also pull the oil cooler feed (be sure you know which is the feed). During cranking, you should get some flow here almost immediately. If not, it's time for diagnostics.

Larry

FYI, If you are trying to test oil pressure, be advised that the oil cooler port in the center of the accessory case goes directly into the oil pump on the outlet side. So removing that hose from the cooler or the accessory housing will give a direct eye to the pump output flow, when cranking the engine over with the starter or when pulling it through by hand.
In addition, if you are having problems with getting oil pressure when cranking the engine with the starter, remove the top engine spark plugs and crank with them removed. Oil pressure should come up fairly quickly when cranking with the plugs removed.
Good luck,
Mahlon
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