Can you test oil pressure without the engine running?

[1970excursion]

Is there a way to test oil pressure without the engine running?

cranking it by hand work?

 

[bax]

No. You can spin the pump shaft to see it the pump is good but thats about it.

 

[psjoyal]

Not to disagree, but sure you can . A quality (powerful) 1/2-inch drive, reversible drill will generate as much oil pressure as the engine would if running. As bax indicated, you do so by spinning the oil pump drive shaft. With the distributor out, use a 1/4" drive adapter in the drill, a 6" extension, and a 1/4" socket (5/16" for 351w or other Ford) to connect to the oil pump drive shaft. Run the drill in reverse and hang on. This is the same procedure for priming the oiling system on a new engine.

Philip

 

[needabronco]

Do you know exactly how fast your drill spins? To properly diagnose oil pressure you would need to know what RPM your spinning. Yes that's a way to get oil pressure but a weak pump will make good pressure high rpm's yet hardly put out anything at an idle. Kind of hard to duplicate with a drill.

 

[Devin]

Do you know exactly how fast your drill spins? To properly diagnose oil pressure you would need to know what RPM your spinning. Yes that's a way to get oil pressure but a weak pump will make good pressure high rpm's yet hardly put out anything at an idle. Kind of hard to duplicate with a drill.

What he said. You aren't going to know how fast you are spinning it with most drills. Hard to duplicate what your engine will be doing.

 

[bmc69]

You cannot test for anything but pump function, as in 'yes or no', with a drill. And that pre-oils the engine too, of course..the only reason for doing it in the first place.

The actual oil pressure an engine will experience running cannot be known to even a rough degree without every rotating part spinning in its journal bearing.

 

[psjoyal]

Do you know exactly how fast your drill spins? To properly diagnose oil pressure you would need to know what RPM your spinning. Yes that's a way to get oil pressure but a weak pump will make good pressure high rpm's yet hardly put out anything at an idle. Kind of hard to duplicate with a drill.

Not with a Ford pump. With a gear-type pump, like most GM, rpm has a direct effect on output. Ford's use a gerotor pump, which is a positive displacement pump. They put out 80-90% of the pressure and volume they will generate at only 1,500 rpm pump speed. That is why you do not see a linear, continuous increase in pressure vs. rpm with a gerotor pump, like you do with a standard gear pump.

 

[psjoyal]

The actual oil pressure an engine will experience running cannot be known to even a rough degree without every rotating part spinning in its journal bearing.

The spinning in the journals has nothing to do with the pressure generated.

Back to the original question: the OP asked for a way to test oil pressure without running the engine. I assure you, if you prime your oiling system as I said in the 3rd post, with a mechanical gauge hooked up, you will see within +/- 5 psi of what it will put out while running cold. The only thing you won't simulate is hot oil pressure, which obviously is lower than when the oil is cold.

25-40 engines per year tested this way, just prior to firing up on my old SuperFlow SF901 engine dyno.

 

[bmc69]

The spinning in the journals has nothing to do with the pressure generated..

The spinning of the journals has EVERYTHING to do with the flow resulting. The pressure is directly related to the flow. Lets go..tribology engineer here.

You can prove that the pump puts out 'something' by spinning it and watching the gage..but you will never have the first clue what the running engine oil pressure will ever be by spinning a pump with a drill. Heck...the olden day engines used zero oil pressure hot..the guages only registerd to 4 or 6 psi. Spin those pumps with a drill and you will see all kinds of pressure.

 

[bmc69]

Not with a Ford pump. With a gear-type pump, like most GM, rpm has a direct effect on output. Ford's use a gerotor pump, which is a positive displacement pump. .

BS. The only difference between a straight gear and a gerotor pump is the ratio of mesh or interference area to swept volume.

I design both.

 

[psjoyal]

..engineer here.

Yea...that pretty much sums it up. :-*

How about this...go run your engine and check your oil pressure. Now pull the distributor and drive it with a good 1/2" drill. Tell us what you see. Talk about it all you want. The horse is dead...beat it for all I care.

Sheesh guys. %) The original poster asked if it could be done. It can.

No offense intended in my original posts. As for the engineer...yea, I don't really care.

 

[bmc69]

Yea...that pretty much sums it up. :-*

How about this...go run your engine and check your oil pressure. Now pull the distributor and drive it with a good 1/2" drill. Tell us what you see. Talk about it all you want. The horse is dead...beat it for all I care.

Sheesh guys. %) The original poster asked if it could be done. It can.

No offense intended in my original posts. As for the engineer...yea, I don't really care.

I'll say it again, You can tell nothing whatsoever about what your running engine oil pressure will be by spinning a pump with a drill. You, my smart assed newbie fellow, need to go away and find the irrefutable evidence to the contrary and come back here and share it with us.

Funny ting too..before I became an engineer I spent 6 years as an automotive machinist..building a fair number of race engines along the way. Heck..that was what made me decide to go back to school and become injuneer. Picked a crappy school though..Purdue. ;D

And because I still like building engines for fun?..got a 2500 sf shop filled with machining equipment to do just that.

Waiting for the next 'oh..an engineer' snide comment. Might want to do a little searching on here before you do..but I've already got you pegged for someone who won't bother.;D


And Merry Christmas, by the way. Whether anyone thinks they can test their oil pressure matters less than whether they have enough brandy on hand..today.

 

[needabronco]

Not with a Ford pump. With a gear-type pump, like most GM, rpm has a direct effect on output. Ford's use a gerotor pump, which is a positive displacement pump. They put out 80-90% of the pressure and volume they will generate at only 1,500 rpm pump speed. That is why you do not see a linear, continuous increase in pressure vs. rpm with a gerotor pump, like you do with a standard gear pump.

So that's why at idle I have 40-50 PSI in oil pressure and at 2500 RPMs I see 80-90 PSI? Hmmm????%) Maybe my pressure guage is broken? Maybe my Ford oil pump doesn't work, I don't know... Oh, and I'm not an engineer, I just know how to build an engines.;D

 

[DirtDonk]

Until last year I would have agreed with the "same pressure at any rpm" argument. All the Ford 302's and 351W's I've worked with would keep the same pressure at idle as at 3000 rpm, gaining a little at higher rpm, but not losing any at sub-idle speeds. The readings would only changed from cold to hot.
All of which would be pretty much expected, I would think, with a dampened gauge movement.

That was until a buddy hooked up a mechanical gauge to his stock 289 in a '67 EB and I sat there with my mouth hanging open (and not one drop of Eggnog pizza spilled I might add) watching that darn gauge go up and down like a tachometer from 15 to 75 psi. Or, as in my other experiences, just like a typical old-time GM pressure gauge.
Quite the surprise to me, but accepted at face value for what it was.

And not to rub salt in the fire (can you do that?), but just how much of a difference would you expect between a static pump test and a full dynamic engine run? I would have thought you could get a pretty accurate and consistent picture of what your working pressure is going to be.
In a new engine with no internal leaks, wouldn't it at least be close? Assuming you could get it up to a reasonable "idle" rpm (375 shaft rpm or so?), wouldn't it have the potential to be pretty darn close to a fully running engine? Granted, the mains and rods would have different characteristics, but why can't the pressure follow flow?

Just what are you looking out for 70excursion? New engine or used? Testing pump function, or wanting to know what the actual running pressure is going to be with an old engine you're wanting to fire up in the near future? Or just looking for potential leaks perhaps?

Paul

 

[bax]

How come we have not argued about oil 's viscosity yet? say 10 weight vs 40 weight same test? What if you have a spun bearing and its current position is blocking off an oil passage = higher pressure not turning and lower pressure turning. The motor has to be warm and running before you really know what you have. Cold start , thick oil = oil pressure. hot motor thin oil = lower oil pressure. BMC is 100 percent on target. There is no way to tell what pressure you are going to get with a non running engine.

 

[bmc69]

I'm trying to find a nice 'short version' reference that explains how journal bearings function. The shortest version is simple: You will be amazed at the pressures that are developed in the bearing and you will understand how the flow demand for a given bearing is generated. Its a not-so-trivial function involving diameter, width, diametral clearance, relative surface speed, and oil viscosity.

Interestingly..note the two terms are not included: supply (engine) oil pressure and any load applied to the bearing. To a layman, those two that are not involved in calculating bearing load capacity and oil flow requirement are the ones they want to focus on. Intuitively speaking..that is understandable.

 

[bax]

Bill I already said you were right, You don't have to make me feel stupider will all the fancy words.

 

[bmc69]

Bill I already said you were right, You don't have to make me feel stupider will all the fancy words.

But Bax..there is right and then there is right. You know I'm right.

 

[Devin]

I wonder if psjoyal even knows what tribology means. %)

Dang Engineers. We are a "stupid" bunch. (well, ok - I am a bit stupid, but most of us are fairly smart ).

 

[DirtDonk]

What parts of the engine does the oil go through before it gets to the pressure sender? And do components after the sender have the same effect on the overall pressure at the sending unit port as components before the port do? Since it is a system, I presume that there is an effect. Just not sure how much each segment has.

Paul