Can You Pre-Prime the Oil Pump if the Starter Won't? - Page 2

Pavlo · 11-03-2009, 10:41 AM

On my own car it probably gets 40 seconds on the starter to prime the oil system on an oil change, it would get this probably 8 times a year, and it hasn't been a problem, the motor barely gets warm to the touch, certainly not hot. The current drawn by the motor will be much less with the plugs out than in. I wouldn't crank it for so long with the plugs in, the little battery wouldn't take it for a start.

Merp · 11-03-2009, 03:58 PM

KillerB, those figures are starter rpm, not engine rpm. Experience with electric motors, yea, sure.

gto7419 · 11-03-2009, 05:10 PM

KillerB - think about just starting the car without priming. you now have load at all bearing surfaces - with oil still not there to replace the engine lube you are displacing.

Priming without load allows oil to reach the passages. Although it might be a small amount of oil, it decreases the risk of the bearings being damaged when there is load. Plus, pressurizing passages that already have 2.1+ psi is bound to happen sooner than trying to pressurize completely empty oil passages.

Merp · 11-03-2009, 08:28 PM

Also, the unloaded cranking is somewhere around 500 engine rpm depending on the starter gear ratio, so it is not only less load on the bearings, it is also a similar amount of revolutions, at a lower speed, hence why it takes longer to get up to pressure.

For a daily driver, I'd much rather have a slight chance of burning out a starter than spinning a rod bearing.

the suicidal eggroll · 11-03-2009, 08:37 PM

Quote:

Originally Posted by Merp

Also, the unloaded cranking is somewhere around 500-600 engine rpm, so it is not only less load on the bearings, it is also a similar amount of revolutions

How is 1 second at 1500 RPM a similar amount of revolutions as 45 seconds at 600 RPM?

Merp · 11-03-2009, 09:00 PM

How is 1 second at 1500 rpm anything like what we've been discussing?

I've never done it, so I can't comment with certainty, but those who have started unprimed motors said 5 seconds or so at nearly 2000 rpm.

2k*5 = 10k/60 = 166 revs is similar to 0.5k*30 = 15k/60 = 250 when you consider the life in revs of a motor, and the fact that it was previously stated to be nearly thirteen times that difference at 30s, ~6 @ 15.

After a closer look at the manual, it looks like the ratio is around 9 or 10:1, meaning even lower unloaded rpm that I had thought.

the suicidal eggroll · 11-03-2009, 09:22 PM

I was under the impression that it took about 1 second for pressure to build, maybe that's not the case.

What do you think about the cam companies that specifically state to NOT crank the motor like this before starting on a fresh build, that you should start the car up instantly and bring it straight to 2-3k RPM to get oil to the mating surfaces as soon as possible.

wrxsti.l · 11-03-2009, 09:34 PM

Buy an accusump

KillerBMotorsport · 11-03-2009, 09:39 PM

Quote:

Originally Posted by Merp

KillerB, those figures are starter rpm, not engine rpm. Experience with electric motors, yea, sure.

Your're correct... My bad, and I took those figures from the non-turbo page so lets fix it. These are for an STi:

No Load = 2,860 RPM (or more) starter speed --> 9 teeth on starter pinion, 120-ish (I think) teeth on flywheel = 220 Engine RPMs

Load = 860 RPM = 67 Engine RPM... Can this be right?

Anyone got a flywheel to count the teeth on? Or happen to KNOW how many teeth? I can't find it in the service manual and these numbers seem way low!! Once we get this we can put the topic to rest.

It looks like engine RPMs, even with no load, would be way below where the pump is efficient. If the Engine is truly spinning this slow it no wonder it takes so freakin long to to get the 2 PSI light to go off.

Merp · 11-03-2009, 09:40 PM

It does seem a bit low, could have been whatever test method they used to grab those specs. I'd suspect the actual loaded cranking is somewhere between 100-150rpm just based on typical cranking numbers for other cars, but it will vary with the type of motor and starter.

I think I might have a FW in the garage, I'll check it if nobody chimes in.

Regarding the cams, I'd call them and talk to their engineers.

fwiw, after an unloaded prime, I get plenty of pressure in the heads, enough to discover a leaky avcs banjo last time. So I don't think its as much an issue of getting the cams lubricated as it is running them in at the elevated rpm.

In that case, it'd probably be best to prime/pressurize by some other means. Accusump would be a great choice.

the suicidal eggroll · 11-03-2009, 10:03 PM

Quote:

Originally Posted by KillerBMotorsport

Anyone got a flywheel to count the teeth on? Or happen to KNOW how many teeth? I can't find it in the service manual and these numbers seem way low!! Once we get this we can put the topic to rest.

Here you go:
http://www.thesuicidaleggroll.com/hosting/IMG_0070.jpg

williaty · 11-03-2009, 10:14 PM

124 teeth

KillerBMotorsport · 11-04-2009, 08:47 AM

Quote:

Originally Posted by williaty

124 teeth

OK so then the numbers I posted with my 120 teeth FW guestimate will be a touch lower.

I honestly had no idea the motor cranks THAT slowly. Good thread.

48mpg · 11-04-2009, 10:40 AM

too bad there is no real place for suby engines to have one of these

http://paceperformance.com/index.asp...&ProdID=113715

Gixxer1K · 11-04-2009, 01:53 PM

Sounds like a right angle impact wrench will work great then, since it should turn it over around 2000 rpm.

Gixxer1K · 11-04-2009, 01:54 PM

Quote:

Originally Posted by the suicidal eggroll

I was under the impression that it took about 1 second for pressure to build, maybe that's not the case.

What do you think about the cam companies that specifically state to NOT crank the motor like this before starting on a fresh build, that you should start the car up instantly and bring it straight to 2-3k RPM to get oil to the mating surfaces as soon as possible.

I think that's legit. Why spin the cams if cranking isn't going to get oil pressure up there quickly.

BAN SUVS · 11-09-2009, 12:14 AM

Just out of curiosity, is there any indication anywhere that a few seconds of "dry" running before the oil primes are harmful to an engine that was assembled properly with lube? Or is this much ado about nothing?

CKxx · 11-09-2009, 12:46 AM

My non-professional opinion is that w/o plugs the starter can crank for quite a while before you do damage. Just listen to it...

soon2bblackongold · 11-09-2009, 11:54 AM

Quote:

Originally Posted by the suicidal eggroll

I agree
I know the Kelford installation instructions specifically state to NOT crank the motor over and over and over without firing to build up oil pressure, because it takes too long and you'll do more damage to the contact surfaces than if you just fire it up dry (well, not dry, since you have the assembly lube on there).

I mean it takes how long to get oil pressure on a fresh build starting dry? 1 second? At 1500 RPM that's 25 revolutions. I'm 100% sure that cranking the car for 15 seconds at a time, 3 separate times, is a LOT more than 25 revolutions, and the end result is still only 2-3 psi of oil pressure.

+1234

smoky · 11-10-2009, 12:27 AM

I had the same problem tonight, no pressure with the starter even after 1 minute (no spark plug). Since it is my first build I didn't want to start it with no oil pressure, too risky...

I had an idea that solve the issue, let's build pressure in the crank case to help the oil pump. You need to know your crankcase ventilation system, but that's pretty easy with the help of someone. In my case I had hoses for my catch can, I simply capped the head breather (at intercooler) and then plug the crank breather to the air compressor at 40 psi. Pushed a bit of air in the crank and made sure there was no leak. Then I started the car while my father was pushing air in the crank, it took 2 sec to get the oil light and about 10 sec to get 75 psi. With that trick there is no reason to not prime your engine all the time.

It is late, so we'll wait until tomorrow to fire it up!

Hope this help.

BAN SUVS · 11-10-2009, 12:33 AM

Quote:

Originally Posted by smoky

With that trick there is no reason to not prime your engine all the time.

Sure there is, and it's been outlined in posts above. The reason is that you spin the engine fewer times with no oil by just firing it up, than by trying to "prime" the oil pump.

Merp · 11-10-2009, 05:35 AM

Quote:

Originally Posted by BAN SUVS

Sure there is, and it's been outlined in posts above. The reason is that you spin the engine fewer times with no oil by just firing it up, than by trying to "prime" the oil pump.

Try actually reading the thread next time.

First of all, it's been determined that the starter spins much slower than cold idle speed, so the number or revolutions is close, if you run the math on the supposed 10 seconds needed while pressurizing the crankcase, it's actually much less revolutions than a cold start.

Second of all, the problem isn't so much the amount of revolutions as it is the amount of bearing load without oil flow. No plug cranking only loads the mains with gravity, and the rods with inertia loads, vs both compression and combustion loads during starting.

Quote:

+1234

1. Cranking should be done in one shot provided the starter doesn't heat up (mine didn't).

2. 1 second? 1500rpm? Not likely.

3. End result for me was 30psi, and great looking bearings immediately afterwards.

4. Again, the Kelford instruction depends if the dominating factor is lubrication or the need to run the cams in at a certain RPM.

Pavlo · 11-10-2009, 07:02 AM

That is exactly what I recommended earlier in the thread as a possible solution to the "non-priming" engine. And lo and behold it works!

Quote:

Originally Posted by smoky

I had the same problem tonight, no pressure with the starter even after 1 minute (no spark plug). Since it is my first build I didn't want to start it with no oil pressure, too risky...

I had an idea that solve the issue, let's build pressure in the crank case to help the oil pump. You need to know your crankcase ventilation system, but that's pretty easy with the help of someone. In my case I had hoses for my catch can, I simply capped the head breather (at intercooler) and then plug the crank breather to the air compressor at 40 psi. Pushed a bit of air in the crank and made sure there was no leak. Then I started the car while my father was pushing air in the crank, it took 2 sec to get the oil light and about 10 sec to get 75 psi. With that trick there is no reason to not prime your engine all the time.

It is late, so we'll wait until tomorrow to fire it up!

Hope this help.

11-03-2009, 03:58 PM	#27
Merp Scooby Newbie Member#: 199106 Join Date: Jan 2009 Location: Merrple Town, Pennsyltucky Vehicle: red Le Tour 700 5mt E85 HTA68 STi Wagon	KillerB, those figures are starter rpm, not engine rpm. Experience with electric motors, yea, sure. Last edited by Merp; 11-03-2009 at 04:20 PM.

11-03-2009, 08:28 PM	#29
Merp Scooby Newbie Member#: 199106 Join Date: Jan 2009 Location: Merrple Town, Pennsyltucky Vehicle: red Le Tour 700 5mt E85 HTA68 STi Wagon	Also, the unloaded cranking is somewhere around 500 engine rpm depending on the starter gear ratio, so it is not only less load on the bearings, it is also a similar amount of revolutions, at a lower speed, hence why it takes longer to get up to pressure. For a daily driver, I'd much rather have a slight chance of burning out a starter than spinning a rod bearing. Last edited by Merp; 11-03-2009 at 08:38 PM.

11-03-2009, 09:00 PM	#31
Merp Scooby Newbie Member#: 199106 Join Date: Jan 2009 Location: Merrple Town, Pennsyltucky Vehicle: red Le Tour 700 5mt E85 HTA68 STi Wagon	How is 1 second at 1500 rpm anything like what we've been discussing? I've never done it, so I can't comment with certainty, but those who have started unprimed motors said 5 seconds or so at nearly 2000 rpm. 2k5 = 10k/60 = 166 revs is similar to 0.5k30 = 15k/60 = 250 when you consider the life in revs of a motor, and the fact that it was previously stated to be nearly thirteen times that difference at 30s, ~6 @ 15. After a closer look at the manual, it looks like the ratio is around 9 or 10:1, meaning even lower unloaded rpm that I had thought. Last edited by Merp; 11-03-2009 at 09:15 PM.

11-03-2009, 09:40 PM	#35
Merp Scooby Newbie Member#: 199106 Join Date: Jan 2009 Location: Merrple Town, Pennsyltucky Vehicle: red Le Tour 700 5mt E85 HTA68 STi Wagon	It does seem a bit low, could have been whatever test method they used to grab those specs. I'd suspect the actual loaded cranking is somewhere between 100-150rpm just based on typical cranking numbers for other cars, but it will vary with the type of motor and starter. I think I might have a FW in the garage, I'll check it if nobody chimes in. Regarding the cams, I'd call them and talk to their engineers. fwiw, after an unloaded prime, I get plenty of pressure in the heads, enough to discover a leaky avcs banjo last time. So I don't think its as much an issue of getting the cams lubricated as it is running them in at the elevated rpm. In that case, it'd probably be best to prime/pressurize by some other means. Accusump would be a great choice. Last edited by Merp; 11-03-2009 at 09:48 PM.

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11-03-2009, 10:41 AM	#26
Pavlo Scooby Specialist Member#: 23015 Join Date: Aug 2002 Location: Wellingborough, UK Vehicle: 95-> GC8 Black, blue and blue	On my own car it probably gets 40 seconds on the starter to prime the oil system on an oil change, it would get this probably 8 times a year, and it hasn't been a problem, the motor barely gets warm to the touch, certainly not hot. The current drawn by the motor will be much less with the plugs out than in. I wouldn't crank it for so long with the plugs in, the little battery wouldn't take it for a start.

11-03-2009, 05:10 PM	#28
gto7419 Scooby Specialist Member#: 44256 Join Date: Sep 2003 Chapter/Region: Tri-State Location: Long Island, NY Vehicle: 2002 WRX Wagon	KillerB - think about just starting the car without priming. you now have load at all bearing surfaces - with oil still not there to replace the engine lube you are displacing. Priming without load allows oil to reach the passages. Although it might be a small amount of oil, it decreases the risk of the bearings being damaged when there is load. Plus, pressurizing passages that already have 2.1+ psi is bound to happen sooner than trying to pressurize completely empty oil passages.

11-03-2009, 09:22 PM	#32
the suicidal eggroll NASIOC Supporter Member#: 51961 Join Date: Jan 2004 Chapter/Region: TXIC Location: San Antonio, TX Vehicle: 2005 STi 2001 Nissan Sentra	I was under the impression that it took about 1 second for pressure to build, maybe that's not the case. What do you think about the cam companies that specifically state to NOT crank the motor like this before starting on a fresh build, that you should start the car up instantly and bring it straight to 2-3k RPM to get oil to the mating surfaces as soon as possible.

11-03-2009, 09:34 PM	#33
wrxsti.l Scooby Specialist Member#: 156973 Join Date: Aug 2007 Chapter/Region: International Location: Adelaide, Australia Vehicle: 2002 ADM WRX STi STi Black/Blue	Buy an accusump

11-03-2009, 10:14 PM	#37
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	124 teeth

11-04-2009, 10:40 AM	#39
48mpg Scooby Specialist Member#: 58405 Join Date: Mar 2004 Location: So.Fla. Vehicle: 2004 Element GT65'd Hydra, Hydramist'd STi	too bad there is no real place for suby engines to have one of these http://paceperformance.com/index.asp...&ProdID=113715

11-04-2009, 01:53 PM	#40
Gixxer1K Scooby Specialist Member#: 81631 Join Date: Feb 2005 Chapter/Region: NWIC Location: Seattle area Vehicle: 2002 WRX BC 272s HTA68	Sounds like a right angle impact wrench will work great then, since it should turn it over around 2000 rpm.

11-09-2009, 12:14 AM	#42
BAN SUVS Scooby Specialist Member#: 28685 Join Date: Nov 2002 Location: Reno, Nevada Vehicle: 1993 L wagon swapped w/ 2001 OBS	Just out of curiosity, is there any indication anywhere that a few seconds of "dry" running before the oil primes are harmful to an engine that was assembled properly with lube? Or is this much ado about nothing?

11-09-2009, 12:46 AM	#43
CKxx Scooby Specialist Member#: 33458 Join Date: Feb 2003 Chapter/Region: Tri-State Location: West Chester, PA Vehicle: 1988 Justy 1.2L 4WD 2002 WRX 2.1L AWD	My non-professional opinion is that w/o plugs the starter can crank for quite a while before you do damage. Just listen to it...

11-10-2009, 12:27 AM	#45
smoky Scooby Newbie Member#: 221439 Join Date: Aug 2009	I had the same problem tonight, no pressure with the starter even after 1 minute (no spark plug). Since it is my first build I didn't want to start it with no oil pressure, too risky... I had an idea that solve the issue, let's build pressure in the crank case to help the oil pump. You need to know your crankcase ventilation system, but that's pretty easy with the help of someone. In my case I had hoses for my catch can, I simply capped the head breather (at intercooler) and then plug the crank breather to the air compressor at 40 psi. Pushed a bit of air in the crank and made sure there was no leak. Then I started the car while my father was pushing air in the crank, it took 2 sec to get the oil light and about 10 sec to get 75 psi. With that trick there is no reason to not prime your engine all the time. It is late, so we'll wait until tomorrow to fire it up! Hope this help.