Can you test oil pressure without the engine running?

[broncnaz]

My georotor pump or gauge must be broken as well as it increases pressure when I rev it up. Maybe its my self givin redneck engineering degree thats the problem

While I agree gerotor pumps do have limits on the volume and PSI they are still based upon RPM speed. If there was no increase in volume or PSI there would be no need for a relief valve and once you got some wear in the bearings oil pressure would pretty much drop to nothing as the pump would not be able to compesnsate.
Not real sure but I would say that oil pump RPM would only be about 1/3 maybe less than that of actual engine RPM. but just turning the pump and getting oil pressure really tells little as has been stated. Hell you could have spun bearings and get great oil pressure. But the engine would be junk.

 

[DirtDonk]

Wouldn't the speed be exactly half crank speed? Since it's direct-driven by the distributor shaft, it should be at half-speed.
Methinks anyway.

Paul

 

[ryoungbronco]

Just did this two weeks ago, right before starting the engine for the first time. I was only looking to see if the oil pressure read on the gauge. I hooked a primer to my power drill and spun it while the ignition was on "on". I watched the gauge go up between 40 and 70 psi so I knew I was good.

 

[broncnaz]

Wouldn't the speed be exactly half crank speed? Since it's direct-driven by the distributor shaft, it should be at half-speed.
Methinks anyway.

Paul

I guess the dizzy turns 1/2 speed as well I was thinking there might be a differance due to cam and dizzy gear sizes and tooth counts. but it stands to reason its 1/2 engine speed.

 

[1970excursion]

watching that darn gauge go up and down like a tachometer from 15 to 75 psi.
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

Merry Christmas,

Motor in question is from my rock crawler that was built about 8 years ago.

It started as an 80's 351w, I bought it from a guy that abandoned his project, so I dont really know what all was in it, It was my first motor I ever put together and basically just slapped all of the parts together the guy gave me. Anyways it always had about 15-20 psi on a mechanical guage at idle, hot or cold (I think motor has been on the stand for a few months now) The pressurer would raise with the RPM. never had a problem with knocking or an audible indication of low or no oil pressure.

I want to put this motor in my Bronco now, and started to think about the oil pump issue, and is why I asked if you could test it, while on an engine stand.

 

[needabronco]

Well, sense it's on a stand, oil pumps are cheap! All you have to do is drop the oil pan and R&R the pump. Should only be $20-30 for the pump and $15-20 for a new pan gasket, unless your's is already the re-usable rubber ones...

If you suspect the pump is bad or weak, there's never an easier time to swap it now! When your laying on your back and spent an hour fighting to get to oil pan out, and with oil dripping on your face you'll be wondering why you waited...

BTW you only need a standard volume pump, Ford oem spec pumps are actually pretty good... Don't buy into the Chevy hype that you need a high volume/high dollar oil pump.

 

[EricLar80]

Picked a crappy school though..Purdue. ;D

That sucks. You should have picked a good engineering school such as Cal State University, Northridge, like I did. :-* jk, of course

All joking aside, it does matter where you go to school when you are at the job interview and at socials, but not so much when actually at work. It matters more that the person "gets it" and can actually apply what was taught in a practical and meaningful manner. Not to say anyone on this board cannot do just that, it is just my managerial spiel.

I am not a tribology engineer, so I have no experience in this area, but I would tend to agree with bmc69 that a bearing in motion could provide different pressure numbers than a stationary one. Hot/cold engine aside, the crank (or whatever - cam, lifter, etc) will rest on the bearing when the engine is not moving, and kinda center itself when the engine is running. This is due to the oil entrapped between the bearing and the shaft. The bearing is only there for the times that the crank or whatever has enough load that it accidentally makes contact with the wall; ideally, the bearing is never used as physical contact = heat & wear. That being said, the clearances change when you have the crank offset in the bearing - remember that the bearing clearance may only be .0005" all the way around, so by offsetting it to one side, you are possibly doubling that number to .001".

However, all that is probably less significant than a cold vs. hot engine on a particular weight oil. %) With the right viscosity (lets say 50w when its 0 degrees F out), it would be easy to produce high oil pressure at any rpm.

Oh, and to get the rpm of the drill figured out, you could use an adjustable timing light and find the point at which the drill seems to be motionless and read the rpm output. Watch out for aliasing.

Eric

 

[patrickmitton]

We were having this same discussion one dayabout 30 years back,As I was standing next to my friends 53 chevy truck...he had just installed a ford 302 !!!. As he was turning it over with the key,I reached in and gave it some gas through the top of the carb...The Engine lit right off..So did the oil through a fitting that was not capped. He had used a Tee instead of a 90 and forgot to cap the 90. For getting sprayed with oil..I really got a laugh

 

[broncnaz]

Merry Christmas,

Motor in question is from my rock crawler that was built about 8 years ago.

It started as an 80's 351w, I bought it from a guy that abandoned his project, so I dont really know what all was in it, It was my first motor I ever put together and basically just slapped all of the parts together the guy gave me. Anyways it always had about 15-20 psi on a mechanical guage at idle, hot or cold (I think motor has been on the stand for a few months now) The pressurer would raise with the RPM. never had a problem with knocking or an audible indication of low or no oil pressure.

I want to put this motor in my Bronco now, and started to think about the oil pump issue, and is why I asked if you could test it, while on an engine stand.

I'd also say it sounds a little on the low side but should be fine many people have even less PSI at idle. but as was said you could put a new pump in before install. While a new standard pump should be fine a HV pump would also be a good choice to help keep more oil in a possible worn engine. There's usually no cost differance between the pump but I would also install a HD pump drive shaft in either case.