Oil Pressure Puzzle

J

james singleton

Well-known member
I installed a new (remanufactured/crate) engine (200c.i.) recently and have several hours of time on the engine; 20 or 30 minutes at a time and everything seemed to be fine! I tested the oil pressure with a drill motor before I ever installed the motor and oil pressure was good. Every time I started and ran the engine I would have oil pressure in the 55-60psi range. Now my idiot light comes on and I have no oil pressure; I even took the nipple off the block where my oil pressure gauge line & idiot light sender goes into; and no oil coming out of the block. It is a new oil pump that I primed before installing and my oil level on the dip stick is full! I'm baffled as to why all of a sudden NO OIL PRESSURE! I did have my vehicle jacked up off the ground a foot or so; first in the front and then in the rear. Can you lose the prime in the oil pump by jacking the vehicle up? I have never had a problem doing that in the past! The only other thing I can think of is that the new oil pump went bad!? Any thoughts from anyone? Thanks!
 
Don't know for sure, but I guess it seems reasonable that you could lose prime on a pump when the car is jacked up, once the level is pulled down due to the oil circulating through the engine. Heck they put trap doors and baffles in the oil pans to keep from starving the oil pump on some cars.
Seems like it should catch prime though when the car is back on level ground. Could it be that drive gear sheared? Isn't the pump driven by the distributor shaft which is turned by the distributor gear?
Doug
 
66fastback, I was already thinking about pulling the distributor out and running a drill motor again (I did this prior to installing the new engine) and checking for oil pressure that way. I will inspect the distributor gears when I take it out; the gears looked pretty good to me when I installed the distributor. Can't you prime the oil pump when the distributor is out by pouring oil down the distributor hole? I primed the oil pump when I first installed it! I guess I need to start eliminating the possibilities. The engine looked very clean inside & out from what I could see when installing the engine; and supposedly the engine is factory hot-tanked, etc.; but I am wondering if any new engine residue could have plugged up the new oil pump? I just may have to pull the oil pan and check the oil pump. My manual mentions "inspecting the oil pressure relief valve and spring, to ensure that it is not sticking or stuck"! It sure seems funny to have real good oil pressure for the first several hours on the engine and then "NO OIL PRESSURE"! Like I said the only thing I have done is jack up my vehicle; both from the front 6-12" and then the rear. Thanks!
 
Also possible, is that the retaining bolt for your pickup has backed out, causing a loss of suction.
 
make sure you haven't over filled with oil. Too much oil gets air mixed in when the crank starts hitting it and you lose oil pressure. Don't ask how I know this :lol:
 
ADDO, That will be something that I'll check if, or when, I remove the oil pan to check the oil pump. Something else that crossed my mind a little while ago is this; I believe that I may have run the engine for a couple of minutes when I had my vehicle jacked-up in front. I had it jacked-up for a couple of days and I believe that I started the engine for a few minutes; wouldn't that possibly cause the oil pump to lose it's prime if the oil pick-up was not submerged? Does anyone know if the oil pump can be re-primed by removing the distributor or the oil filter and pouring some oil down the distributor hole or the oil filter hole? Thanks again!
 
As long as the pick up is in oil the pump will prime. Think of this when you change the oil the pump also drains off.
 
Pull the dizzy and inspect the oil pump drive shaft for twist.

If it looks ok try to prime it with a drill.

The pump pulls from the pan and pumps straight to the filter. You can squirt oil in the galley that leads to the filter or in the hole where the sending unit goes. While you are doing this turn the pump backwards by hand to pull the oil into the pump. A good tight (new) pump should pull as long as the gears are wet with oil. It realy doesn't have to be full of oil.

If it will not prime with a drill I would pull the pan and double check everything on the pump and pickup. You are in too deep to risk hurting it now.
 
Thanks guys for all your suggestions! I will post back when I find out the problem and what worked (hopefully). GTM1086, I get what you are saying about when you drain your oil, but doesn't the oil pump retain it's prime even when you drain your oil? I was thinking that when my vehicle was jack-ed up in front and I ran the engine for a few minutes that if the oil pick-up was not submerged in the oil that the pump would still pump what little oil is in the pump and it might lose it's prime? STUBBY, You are right; I am "in too deep to risk hurting it now"; especially with only a few hours on a brand new engine! Thanks Guys!
 
Some engines can and will lose prime to the oil pump simply by changing oil. I have never experienced this but apparently it can happen.

I am doubtful that this problem was caused by merely elevating one end of the car but I could be wrong. More likely a mechanical failure as mentioned above.
Joe
 
When I got my car the oil pressure was fine, then it would drop off sharply. I replaced the pump, buttoned it back up and the pressure dropped off permanently. The pump shaft was too short and the shoulders were rounded off so it ran briefly and dropped out of the drive gear in the distributor. I solved that problem by getting a new engine because the original ran dry on my test drive and never recovered.
 
NO Jacking the front or the back of the car isn't going to remove all the oil from the pump area.. unless your jacking it up to about a 45+ deg angle.. as the pump is most likely 1/2' to 1' from the bottom of the pan and you have atleast 6" to 8" of oil above that??..
So you pulled the sending unit and started the motor and no oil came out.. If it started and ran then I don't think it the dizzy gear but maybe the pump drive shaft, pump pick up tube, or the pump its self....
***************PLEASE DON'T GET ME WRONG**************
But you do know that when the motor is Off there is no oil prusher, it does not hold prusher just the prime..... So the idiot light would come on when the key is turned on ( motor not running), and oil would not squart of the sending unit.
AGAIN DON'T GET ME WRONG BUT SOME PEOPLE DON'T REALIZE THAT..
*****************************************************
Good luck
tim
 
I would look at the sending unit first. They can fail. I would also put a gauge on it.

Another thing would be to change the filter. A new engine could have junk in it that the builder might have missed, clogging the filter.
 
It should, but there are some cheap filters that are suspect. For instance, I have seen filters clog and then balloon then rupture because the bypass failed.
 
james singleton":vzmkjmps said:
... I even took the nipple off the block where my oil pressure gauge line & idiot light sender goes into; and no oil coming out of the block...
Click to expand...

I presume he did this with the engine running. It just ain't pumping oil :evil: Time for exploratory surgery.
Joe
 
Well I said I would post back when I found the problem with "OIL PRESSURE PUZZLE" (no oil pressure)! I feel a little bit embarassed telling you the problem because I may, or may not have been the source of the problem!? It could have been the manufacturer of the rebuilt engine as well, but here goes: I pulled the distributor and inspected it's gears (good!) and then pulled the oil pump / distributor shaft out to look at it (it was good!); I was getting ready to use a drill motor to run the oil pump and when I went to put the oil pump shaft back in the distributor hole it slipped thru the opening in the side wall and fell into the oil pan! So now I had to pull the oil pan to get the shaft; which as it turned out I would have had to do anyway to find the source of the problem. Here is what I found; a large wad of cotton fiber the size of a softball that was hanging from the oil pick-up. At first it looked just like a big ball of wheel bearing grease hanging from the pick-up; but when I pulled it away I realized it was a cotton fiber material that the manufacturer had used in the shipping crate/box engine. I don't know if they accidently got a piece up in the crank area or whether it was my own careless mistake. I took my time when assembling the timing chain cover, water pump, oil pan, etc.,; I just don't know? I have egg on my face! At the very minimum (even if it came from the manufacturer with a wad up in the crank area) I should have spotted it! Live and learn. I took the oil pump off and cleaned everything real good and inspected bottom end (it looked clean); I also pulled off the new oil filter and replaced it with a new one. I changed the oil as well. The good news is that it is back together and running, and has good oil pressure now (50psi plus). Thanks Guys!
 
Well, clean the egg off your face. It WAS the shaft, pickup, pump -- all starved for oil due to a reason nobody here came up with . Whew. Job done.
 
Coulda sat here all night trying to figure that one out. Would have never guessed... don't feel bad, while I was trying to see if the fuel pump gasket was the right one, I dropped one of the bolts into the pan right before I swore to myself that this would be the last time I had to pull the motor out.
 
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