Rebuilt Engine and Zero Oil Pressure

Those of you who get the "RockAuto" newletter will know this is where the following information came from.

I'd never heard of the "air locked oil pump" syndrome.


New or Rebuilt Engine with No Oil Pressure



Symptoms: No oil pressure on a new or newly rebuilt engine.

Problem: You can generally overcome a no oil pressure situation with normal tricks of the trade: prefill the oil filter, pour oil into the galleys, and spin the engine with the spark plugs out. If nothing else, you can always spin the oil pump with a drill motor and get pressure, right? Not necessarily. Occasionally, an engine comes along that absolutely refuses to generate pressure. Don’t pull the engine out and tear into it again just yet. There is one other fix you can try.

Cause: It is possible to have a completely air-locked oil pump. This is especially true if oil was put into the pan (covering the pickup tube) before it was poured into the galleys from above. The result is an air pocket enveloping the oil pump.

Repair: Fasten a hose to any galley connection on the block. (Example: oil cooler line or oil pressure sending unit.) Attach a funnel to the hose and pour in about a cup of oil. Rotate the engine backward by hand. Each time you move the crank, some of the oil in the funnel should go into the block. If nothing else, this tells you that the oil pump is installed correctly. After reverse-pumping the cup of oil into the block, remove the hose and reconnect the oil cooler line or sending unit to the oil galley. You should now have oil pressure.

NOTE: Most engines will produce between 15 and 35 psi of oil pressure when spinning with the spark plugs removed.

Tech Tip provided by:
Howard Fitzcharles, Technician

 

never had that problem and never heard of that fix before. interesting.

 

i knowed that
i spin the oil pump with a drill motor...at first i thought you were talkin about, your new motor

...Ricks' friend Frank...

 

Damn buddy, I thought you were going to say you got that car back together and had no oil pressure.

 

dang rick, you scared the heck out of me.

 

Me too...

 

I always take the pump apart & put a little bit of STP into the gears, that is, after I check the clearance of the rotors. Even new ones have been known to be off a little. STP in the pump helps pull the oil into the pickup a LOT faster by sealing the rotors up and creating vacuum faster.

 

LOL guys. Not to worry about my engine not having any oil pressure yet - I haven't even ordered the new cam!

I've always used a reverse drill to get the oil pressure up (while I have someone watch the gauge) - but never heard of the "air-locked oil pump".


Just something to store in the punkin if any of us ever needs it (which is NEVER, hopefully).

 

new one on me, but good to know just in case if i ever come across something like this

 

Old engine builder

I know a guy who used to hold the oil pump in a cannister of oil, and run it with a drill to prime the pump prior to installing it. He called it 'testing' but it did prime the pump even though oil ran out of the pickup tube.

Seth

 

I had a pump somehow have loc-tite in it from the factory for a 390. Was a melling HV pump. They replaced it, but never will i install an oil pump w/o tearing it apart first to check inside there.. was a PITA dropping a pan in a 66 f-100

 

Believe it or not I had a oil pump lock up or air lock on me on a fresh 68 302. We tried starting car 2 or 3 times and it would crank real hard and when we left off the key the motor would spin backwards a little. It boggled are brains and thought we would try one more time. The Engine cranked hard again and then started but with no oil pressure. We pulled the distributor out to check the oil pump shaft and it was completly twisted from top to bottom and snapped in the middle. we ran the pump with a drill and had oil pressure. We changed the oil and replaced the dist. with a new shaft and engine ran fine after that with no trouble at all. strangest thing I can remember about building an engine.

 

Same way with the one mentioned above.
It had 13 total twists in it, and broken on one end.
We had primed the system before running, and i had put about 50 miles on it before it locked up

 

Should spin it until you see oil at each rocker arm.

 

I've seen those "twisties" before. They're a sight to behold (if it's not yours that is twisted).


I have a hardened oil pump drive shaft and gear. Some argue that having a stock (soft) driveshaft is a safety net - either way, oil pressure is going to drop if something goes wrong with the pump.