Just check the oil pressure by taking out the oil pressure switch(above the oil filter)and running a manual gauge. Engine started up with 20 psi At 1200 rpm and worked it way down to ten psi in a matter of seconds at the same rpm. If I'm not mistaken if the pump was working well shouldn't it be pumping more psi from that point and then it would decrease through the slop in the bearings if there was any. Could the oil pump be screing up..... Maybe loose pickup or the spring messing up. Or a defective oil pump? What would be the signs of a bad pump? What I want to know is my assumption correct? Shouldn't this pump start up cold should be putting out like 45 to 60 psi and run at like 30?

Im reading the same psi at the top as the bottom???????????
I'm going with defective oil pump.
which would be better if this is the case. High volume or high pressure????? oil pump?
Kenny

 

When driving this vehicle on the highway. It will maintain about 20 psi but as soon as the o.d. kick in it will drop to 0 psi on the gauge. If I put it neutral and rev it it will come back up and drop again. What would happen if the pickup was cracked or damaged in any way. Would I loose psi. I reused the old one. The engine had 150000 on her before I rebuilt her. The reason I pulled her apart was a similar oil pressure problem. She had good pressure for two months............

Any help is greatly appreciated
Kenny

 

As cheap as oil pumps and all the affiliated hardware for them are, there really isn't a reason to reuse old stuff.

Anyway, did you "securily" attach the pick up to the pump? I.e. braze, bolt on bracket, etc? If not, your pickup probably rattled loose and lost its installed height (assuming it was set).

Oil pumps generally don't "go bad." Due to design, they pretty much either work or they don't.

 

When you rebuilt it, what clearances did you measure at the main and rod bearings?

 

I bet his pick up is on the bottom of the oil pan. it makes sense ... when he steps on the gas he starves the oil pump of oil and the presure drops

 

No that don't make sense cause it would suck no oil if the pickup was resting on the pan. Come on, you know better than that.

 

Well I'll find out soon enough I am about to drop the oil pan again just have to brush up on the procedure again
Kenny
p.s. I check the oil pressure by the oil filter and it reads the same as the gauge the top meaning that the oil pump isn't pushing out enough pressure through the filter and the check valve.........

 

Oil pumps don't "push pressure". They push oil.

It's a "constant displacement" type of pump, being as how it's 2 gears. Each time it rotates, it moves some given volume of oil; the same as every other pump with the same gears in it.

Pressure is produced by resistance to that flow. The pump WILL move its "spec" volume of oil, and send it somewhere, since oil is incompressible. Pressure will build up in the passages between the pump and any escape route that the oil can find; ideally, the only escape route available, will be through things like bearing clearances. Once the pump's "spec" pressure is reached (as a result of the pump moving more oil than can escape), the remainder of the oil that it moves, will escape out a spring-loaded bypass; and at that point the pressure will stabilize at a high value.

Sounds to me like it's too easy for the oil to escape from the passages.... most likely because your motor has excessive bearing clearances. If I was the betting kind, I'd bet money you'll find you're wasting your time futzing around with the pump, if you really look at the thing. If you tear it down and just throw away all your time and effort by just changing the pump without finding out what's really wrong with it, I'll give it 1000 miles before something fails catastrophically that you can't mis-identify.

If you have the pan off, I'd strongly recommend looking at all the bearings. At least one is toasted, or is the incorrect one (like a .010" under bearing on a .020" under crank journal).

Procedure = remove pan bolts

 

My friend you are absolutely right. Being that I am a mechanic and work with many knowledgeable mechanics. I have been advised and are aware of all possibilities that could be causing my problem. 1 being wiped out bearing. 2 being a bad spring in the oil pump. 3 being a clogged oil filter/check valve which does happen. 4 maybe the pick up fell off or is cracked................. All I have been looking for is someone to say yeah your bearings are probably wiped but maybe this this and this could be bad too which may cause the same problem. I have my plastigauges on stand by and if there is play the ngine coming out and going right to the machine shop.

And I'm not stupid as your post may imply...............
Im well aware, I was gathering info before I get to the job which is today. So thanx all for your suggestions

and I will tell you what I find.........
Kenny

 

I don't mean to imply stupidity, sorry if I came across that way. Only, get back to the simple things, and don't over-analyze it and outsmart yourself.

Too often, people think that low oil pressure is the result of something wrong with the pump, and that they're going to "fix" it by swapping the pump. But that is only very rarely the case. Emphasis on "very".

The filter bypass valve cannot cause a low oil pressure condition no matter what. Cross that one off your list of suspects. If it sticks open, then the oil pressure wil be slightly higher, because the oil isn't being forced through the filter; if it sticks closed (or is blocked somehow) then the oil pressure will be normal because the oil is all passing through the filter at all times, like what happens when you use the Fram bypass-less adapter. In no possible case will it cause low oil pressure.

Pickups can fall off or break. On the other hand, the hole in the pump is submerged in oil 100% of the time, if everything is right; and doesn't even need the pickup most of the time, because the inlet hole is below the oil level. If you had a problem where the pressure was good but consistently dipped when braking or turning or whatever, then that could be the cause of that symptom; but not full-time low pressure.

One thing that it could be, however, is a blocked pickup screen. Pieces of gasket material or old sludge will do that. That definitely will create a full-time low oil pressure symptom. Problem is, the oil starvation will wipe the bearings; so even if that's the root cause, the bearings are most likely heavily damaged.

Another possible cause is missing gallery plugs in the front of the block, behind the timing gear. See the above paragraph for the inevitable result of such a massive internal oil leak.

But, the most common problem to the constant low-oil-pressure symptom, is bearing clearance.

As a much wiser man than me once said, "The simplest explanation that fits all the facts is usually the right one."

Any way you slice it, I believe you're going to be pulling the crank.

Good luck!

 

thanx for you honest opinion..............
Kenny

 

Now HalfinchWrench you are getting a little jumpy on the come backs. Some of it was my fault, I did not explain my self right. What I ment was that the pickup got loose and and did not fall out of the pump but rotated down untill it rested on the pan. The pick up being so close to the pan oil will not be able to get under it fast enough to pump through the engine.
Now dont you feel bad for dissing me

 

If the pick up came loose you my tac weld the pickup to the oilpump housing. Also worn cam bearings will lower oil psi also.
I dont know if you replaced the cam bearings or not I figur I would through that out there.

 

Just to two more 'could be's'... the pick up could have become contaminated (partially blocked) or the spring could be weak or jammed (as mentioned kinda). The bad thing is if there is 'stuff' blocking and jamming, you are rebuilding. Like RB said, any way you slice it the crank is most likely coming out.

 

well the engine bearings were wiped..... have since sent it a machinist to have everything checked. Got a new crank cut .10 .10 and new set of bearings all around. Re honed the cylinders, got a high volume pump and a new pick. Had the machinist pess in the pick up. New rings as well............................

only thing that sux is that the gasket kit i purchased came with a ripped gasket for the rear main seal plate. what difference would it make if I installed that gasket with permatex or gasket glue??????????

the prob was the oip pum was sucking air $10 part wiped out my bearings......... plus I ordered a new set of crane lifters

thanx for all your help
Kenny

 

RB83L69:
would i get 30+ lbs on startup and 15 lbs untill the oil is HOT if the plugs behind the cam gear were missing. After it is hot, it drops to 8lbs, at 750 rpm.....Do I have to pull apart my whole front half of the motor to see if the plugs are in? my cleearneces are okay, the motor is new and was bluprinted. thanks

 

Wrong, builder error wiped out your bearings.