Would cranking for 10 seconds with the mixture in idle cut off pre oil the engine?

Kiddo's Driver

Kiddo's Driver

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Would cranking for 10 seconds with the mixture in idle cut off pre oil the engine?
Then after waiting xx seconds do a normal start with an oiled engine.
Clearly there is no value in doing this or I would have heard about it before.
 
Kiddo's Driver said:
Would cranking for 10 seconds with the mixture in idle cut off pre oil the engine?
Then after waiting xx seconds do a normal start with an oiled engine.
Clearly there is no value in doing this or I would have heard about it before.
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Clearly there is value in doing this. When you forget to go mixture full rich and it doesn't start, you can turn to the CFI or DPE in the other seat and say "I was just pre-oiling the engine".
 
Generally from starter engagement, engine firing and up to oil pressure rise, the engine may run without sufficient lubrication. The objective of pre oiling is to circulate and coat parts prior to metal to metal friction involved with rotating the engine.

What you suggest won’t do much.
 
No don't recommend that. It might be your only 10 seconds of cranking your battery has left some day.

I try to start mine at the lowest possible idle at first. And my 0-320 with D mag and impulse coupler for both mags fires off at a low idle. 650-700 at first until the oil comes all the way up.
 
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Does you oil pressure come up to normal in 10 seconds? Mine doesn’t. I pre-oil by removing plugs to improve cranking speed and cranking 2-3 times for about 30 seconds each.
 
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An engine only needs to be pre-oiled if it doesn't already have oil in it. Like freshly overhauled, first start but even then it's got assembly lube, you just want to ensure the pump has picked up the oil and is delivering it. As far as doing on every start you're just going to by buying a new battery and starter sooner than you would have.
 
Silvaire said:
An engine only needs to be pre-oiled if it doesn't already have oil in it. Like freshly overhauled, first start but even then it's got assembly lube, you just want to ensure the pump has picked up the oil and is delivering it. As far as doing on every start you're just going to by buying a new battery and starter sooner than you would have.
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This. Spinning up with the starter is part of what Lycoming recommends for *initial* starts, but not for starts afterwards.

Nauga,
hopefully slick
 
However, the lycoming recommendation for pre starts also includes removing a plug from each cylinder. Allows for faster spin since it’s not fighting compression strokes.
 
Any type of pre-oil should include the cylinders.

Per Salty ; I remove plugs to do so after an overhaul or sitting.

This also permits squirting oil UP to lube cylinder walls.

Most engines I can Oil Pressure in the Green via hand prop alone.

This is to assure the passages are filled with oil.

Cranking will not lube cylinders so it may be counter productive

w/o added lube.
 
Sometimes I forget to turn the mags on, and do this by accident. Once when I first had the plane, I didn't realize what I had done, and thought it was the infamous "hot start". I kept attempting to start for several minutes without success, pausing to let the starter cool. Much cursing ensued, both by me and the pilots behind me at the fuel point.
 
Have anyone ever seen a oil accumulator on a aircraft engine?
They hold a pressurized charge of oil that you release right before starting.
I have seen them on racing engines.
I installed a zero hour lycoming engine 4 years ago. I didn't turn the engine much at all until I started it for the first time.

Edit: First I flushed the oil cooler with a pressurized pump with mineral spirits for hours, probably about 4 hours 2 different days using my parts washer with fresh solvent in it.

Then I used a pressurized oil tank hooked to the oil cooler that purged the oil cooler of all air.
It seemed to workout real well as I had oil pressure instantly as the engine fired right up first try. 882 hours later the engine is running good.
First I flushed the cooler with fresh oil into the bucket. Then I connected it to the engine and pumped fresh oil through the cooler into the engine. I had oil pressure as soon as I turned the key.
I did rotate the engine by hand one time to drain out all the preservative oil out of it before starting.
IMG_8227.JPG

IMG_8226.JPG
 
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Any time any of the old radials I flew, if they sat more than three days, they got pre-oiled with a pressure pot.
 
StraightnLevel said:
"Back in the day", when starting up a cold race engine we would always spin it a few seconds before turning on the ignition, just to get some oil beginning to flow before firing. These were dry-sump engines, though, so if they had sat for any length of time there was no significant amount of oil in the pan until the pump got it moving. It also had the side effect of priming the intake.

No waiting in between, though. I would hold the starter button in, then about two seconds later flip on the ignition while keeping the starter running. Generally, it immediately fired without issue, and the whole process ran the starter about the same time as if it was self-priming and had to spin a second or two to fire.
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We would take the belt off the crank pulley for the oil pump and spin it with a drill motor before first start of the day after pre heating the oil. What a PIA it was but it was worth it back in the day since this stuff was not cheap. Picture is a picture of a picture. This was around 1990.
SDC12939-1.jpg
 
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I did the ‘no plugs spin’ yesterday after fogging the cylinders with oil. (Also after fogging and hand turning the prop a few times.) The old batteries I used could spin the engine with no compression, but couldn’t do it with the plugs in.
New battery arrives Monday. Tried getting a Gill 7242-14, but the ship date is August 26th. Canceled the order and ordered a 242.
I’m going to grab my F350’s batteries & start it today using them.
 
StraightnLevel said:
These were dry-sump engines, though, so if they had sat for any length of time there was no significant amount of oil in the pan until the pump got it moving.
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The oil in the pan does nothing to lubricate the engine until the pump picks it up and pushes it into the galleries. None of the moving parts are beneath the oil surface. Lycomings and Continentals and Franklins might be based on old designs, but they're not splash-lubricated like so many ancient cars were. Even the WW2 Jeeps had splash lube. No pump.
 
My Jodel had an A-65. Those little old Continentals had a habit of losing their oil pump prime, as the oil would slowly seep out past the metal-to-metal interface of the pump cavity cover when the airplane sat for a few days. Then the pump wouldn't suck the oil up and the engine would run dry until you noticed that the oil pressure hadn't come up. I tore the engine apart and found the crank's rod journals worn from this, so I had the crank ground and installed undersize bearings. Then I made this manual preoiler:

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1718987913361.jpeg

It drew oil out of the tank and pumped it, via a check valve (I made that too) into a tee in the oil pressure gauge line. It filled all the galleries and bearing interfaces and backed up into the pump to prime it. Oil pressure was instant at startup.

The preoiler was mounted to the engine mount tubes via Adel clamps. The big hat-like knob was to keep rainwater out of the pump cylinder, as the preoiler sat right under a cowl hinge line. The whole thing was just a mega-primer, like the one you use to pump fuel into the engine for start.

You can buy STC'd electric preoilers. But for most, it's not worth it.
 
Stewartb said:
Does you oil pressure come up to normal in 10 seconds? Mine doesn’t. I pre-oil by removing plugs to improve cranking speed and cranking 2-3 times for about 30 seconds each.
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Every time you fly your plane? Does it sit for months or something?
 
Mikey52 said:
generalaviationnews.com

Do you need a pre-oiler? — General Aviation News

generalaviationnews.com generalaviationnews.com
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Good article.

Someone STC'd a Lycoming cam that was drilled through its length, with crossdrillings in the journals to pick up oil from the crankcase bearings, and deliver it to crossdrillings in each cam lobe just ahead of the cam rise. This positively lubed the cam/lifter interfaces, and if a preioiler was installed it would help get stuff wet before startup.

Lycoming could have bought the patent. They went to roller lifters instead.
 
What engine?
An example, covering several CAT (TCM) engines:

"10-12.3. (edited)
The preferred, and most effective method, of priming the lubrication system is using a preoiler
tank (pressure pot). “Engine Pre-oiling” instructions are provided in Section 5-2.9.
Engines are assembled with a small amount of oil on mating surfaces. Crankcase oil
galleries, cylinder walls, the oil pump, oil filter, oil cooler, and hoses contain no oil on a
freshly assembled engine. The starter is not capable of filling all the empty passages in the
engine with oil before ignition. The seconds that pass before oil pressure is developed can
take hours off the life of the engine.
There may be times when an engine pre-oiler tank is not readily available. The following
alternate priming methods may be used."

"5-2.9. Engine Pre-oiling
See also “Lubrication System Priming” in Section 10-12.3.
WARNING
Do not exceed the starter duty cycle to rotate the engine during
engine pre-oiling. Persistent engagement of the starter to rotate
the crankshaft will exceed the starter duty cycle and may result
in premature starter failure.
1. Install and torque the spark plugs and ignition lead wires according to the “Ignition
System Maintenance” instructions in Section 6-4.9.
2. Verify lubrication lines, fittings, hoses, screens, and filters are in place prior to preoiling.
3. Obtain a 1-gallon capacity bladder-type pressure pot with an output pressure of 50
psi (not to exceed 60 psi).
4. Connect the pre-oiler supply hose to the engine oil pressure output (fitting). It may
be necessary to disconnect the aircraft oil pressure sensor fitting according to the
aircraft manufacturer's instructions.
5. Remove the rocker covers.
6. Open the pre-oiler valve and monitor the rocker arms for oil flow. Depending upon
oil temperature, it may take several minutes to see an indication of oil flow.
7. Close the pre-oiler valve upon verification of oil flow at the rocker arms.
8. Install the rocker covers with new gaskets according to the “Cylinder Installation”
instructions in the primary ICA (Section 1-1.1). Torque the rocker cover fasteners to
Appendix B specifications.
9. Disconnect the pre-oiler supply hose and cap; connect the aircraft oil pressure sensor
to the engine oil pressure output according to the aircraft manufacturer's
instructions."
 
StraightnLevel said:
"Back in the day", when starting up a cold race engine we would always spin it a few seconds before turning on the ignition, just to get some oil beginning to flow before firing. These were dry-sump engines, though, so if they had sat for any length of time there was no significant amount of oil in the pan until the pump got it moving. It also had the side effect of priming the intake.
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This is SOP in IndyCar for cold starts and leak checks in the garage after an engine install, and dictated by the engine manufacturers, Honda and Chevrolet. Since the dry sump reservoir is located above the engine mounted oil pump, it only requires about four seconds of cranking to obtain around 80 lbs of pressure.

Generally the engine coolant temperature after these cold starts is observed until 100°C is reached. After that warmup and on pit lane, a couple of bumps before enabling the ignition system is adequate to build oil pressure.

I can't speak definitely for other racing series, but I've seen this same procedure used for nitro and alcohol burning engines in the NHRA. @Gary Ward can comment on that.
 
Large engine manufacturers use prelubrication pumps in some applications. Caterpillar D399s, some 3516s and 3600 series engines use them. These are all big units that hold a lot of oil. I've never seen one on a 3406 or 3412 They can be driven electrically, pneumatically, or manually by hand. Prelube pumps are heavy unless they are small hand crank units, which would make more sense for aircraft. I don't know if there are any STCs available to add a manual prelubrication pump but I'd could be useful in some applications, especially after an oil and filter change or after sitting for long periods of time. Me? I use Cam Guard. It is approved, proven to help, and it is inexpensive and lightweight.
 
StraightnLevel said:
These were dry-sump engines, though, so if they had sat for any length of time there was no significant amount of oil in the pan until the pump got it moving.
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Uuuh, the oil pump, on a dry sump engine, draws from the oil tank, not the sump. Hence DRY sump.
 
I would think that cranking the engine with no fuel until oil pressure comes up would do nearly as much damage as if it fired up right away. The engine still compresses air, which forces the dry rod bearings against the dry crankshaft and the dry crankshaft is grinding and wiggling around in the dry crank bearings.

Personally, when resurrecting an engine that has been sitting for a long time, I'll pull the spark plugs and liberally apply a light oil in the cylinders and crank the starter until oil pressure comes up. If I was really ambitious, I'd pull the rockers so the valve springs arent forcing the dry lifters to grind against the dry camshaft.

Good idea in theory, but I think the benefits would be negligible if even measurable. I knew of some radial warbirds with electric pre-oilers and drag cars with oil pressure accumulators, which stored pressurized oil in a spring loaded cylinder. You'd open a ball valve right before you start cranking and the oil pressure came up right away before the engine fired. Then shut the valve and the engine's oil pump would re-fill the accumulator and compress the spring for next time.

I guess the added expense, complexity, and possible failure points would have to be weighed against bottom end overhaul cost.
 
What does the oil pressure read?.....It's going to depend on the viscosity of the oil and the OAT.....and the rpm during cranking. If the plugs are out....possibly.
 
Kiddo's Driver said:
Would cranking for 10 seconds with the mixture in idle cut off pre oil the engine?
Then after waiting xx seconds do a normal start with an oiled engine.
Clearly there is no value in doing this or I would have heard about it before.
Click to expand...
you are pumping oil !! probably not doing the starter or battery any favors!! If you do that, remove a top or bottom plugs disconnect the other plug wires shut the fuel off, with no compression is easier on the battery or use a separate battery (aux plug or jumpers) 30 seconds is also bad for the starter (you will burn out the starter) a series of 10 seconds with 60 seconds rest / cool down for the starter in between the 10 seconds, watch the oil pressure gage to see pressure.
 
moparrob66 said:
I would think that cranking the engine with no fuel until oil pressure comes up would do nearly as much damage as if it fired up right away. The engine still compresses air, which forces the dry rod bearings against the dry crankshaft and the dry crankshaft is grinding and wiggling around in the dry crank bearings.
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The compression pressure is around 130 psi. Less than that in many engines. Combustion pressures can hit 800 or 1000 psi, considerably lower at idle, of course. Cranking the engine is much easier on it than running it, but the cranking speed is so low that there is little oil pressure, so little oil reaching important areas, and certainly not the cam lobes in a Lyc. Those rely on oil flung off the crankshaft, and at cranking speed there's just too little centrifugal force to do that.

Tear down an engine sometime. One that has sat for a year since it ran. You will find oil between the crank and rod and main bearings. It doesn't all run out. Capillary action keeps enough there for starting. If it didn't, there would be an awful lot of engine failures due to the accumulated bearing wear during cranking.

Some people are seriously overthinking this.

In the flight school I bought Lycoming factory overhauled engine. They had been run in a test cell for 20 or 30 minutes at the factory, then the oil drained and anticorrosion storage oil was put into it. Lots in the crankcase, lots in the cylinders. I drained all that out and put straight mineral in for break-in. With the plugs out, I motored the engine with the starter until the pressure came up a little, then put the plugs in and started the engine. That was the last time that engine ever got any preoiling, and every engine reached TBO with no metal in the filters and compressions in the high 70s. Good for another 1500 hours on some homebuilt.
 
Agreed. The difference in lubrication between fuel off cranking and just starting it would be negligible if even measurable.
 
StraightnLevel said:
A dry sump system has multiple pumps. Generally at least one scavenge pump that pulls from the sump and feeds the tank, then another that pulls from the tank and feeds through the filter and cooler back to the engine. Some have additional pumps for intermediate stages or multiple scavenge ports.

The "dry sump" is rarely if ever actually dry, it just doesn't hold very much at any given time when the engine is running.
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True. But the scavenge pump only pumps the oil to the tank. Not to the engine.

NO engine is dry inside. There is a fog of oil from things squirting, flinging, slinging and otherwise stirring around. :D
 
If the process in the OP was the best procedure, I fully expect that it would documented in the POH.

Turning it over with the starter sort of uses up the oil film between bearings and journals. When starting the engine, it is also being used up, but it is in the process of starting, so that the higher RPM of a running engine can restore oil pressure quicker, thus replenishing the bearing/journal oil film.

True preoiling is a different process. In that process you are forcing oil to the journals without the engine turning at the same time, this using up the oil film. True preoiling would be a good thing.
 
Dan Thomas said:
Those little old Continentals had a habit of losing their oil pump prime, as the oil would slowly seep out past the metal-to-metal interface of the pump cavity cover when the airplane sat for a few days.
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One of the reasons that can happen is due to corrosion and pitting because the accessory cover in which the oil pump gear bores are was magnesium alloy. The new ones are aluminum (and quite a bit heavier)
 
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