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Oil pressure, or lack there of on fresh 1275

64nailhead

Freshman Member
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I have a recently completed motor rebuild that i'm getting no oil pressure from the gauge port. I installed a new filter of course, and have cranked on it for approx 20-30 seconds without getting any oil pressure. Question : how long should it take for it to develop oil pressure at the port?

The build has been going on since 2014, so the exacts of the build are not on the tip of my tongue. But I followed the manual closely. It has new oil pump, rod, main and cam bearings. All crank bearing clearances are at .0015-.0020. I believe the pickup is fine, but can check. I'm not scared to pull the motor back out as it's pretty quick and easy. I was thinking that I should be able to pull the rockers, dizzy and timing chain and spin the cam to drive the pump to see what gives.

Any thoughts or advice is greatly appreciated.
 

Rhodyspit75

Jedi Knight
Silver
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Don’t panic. I had to take the bolt out of the banjo fitting at the end of the tube from the filter. Then pour oil in the hole. You may have to do it more than once, I did. That primes the pump and should give you pressure.
 

zabond

Freshman Member
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if you cant get pressure after priming as Rody said check that the pressure relief valve is ok, maybe a prob after a long rebuild but I doubt it
Russ
 

Rut

Obi Wan
Gold
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These engines along with MGB engine can be hard to get OP going and you may have to prime several times. Pull your plugs, squirt a little oil into the cylinders and crank away. Watch the gauge for any sign of movement and don’t crank too long any one time. Once you build pressure, install the plugs and get ready to break the engine in.
Good luck, Rut
 
D

Deleted member 8987

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We've had reluctant engines in the shops over many decades. Happens.
What our fall-back solution was, with no teardown, was to pull the OP sender (or gauge line), if you have a PCV, unplug it, oil cap on, wrap a rag around the port, with an air nozzle apply some air pressure (you do not want to oil can the sump) while an assistant cranks it.

Air pressure pushed down on the oil, forcing it into the pickup in the sump, cranking keeps the pump from blocking flow, and open port allows it to vent. Without that open port, you're pressurizing a sealed vessel.

Try to get your mechanics to understand THAT.
 

Rut

Obi Wan
Gold
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We've had reluctant engines in the shops over many decades. Happens.
What our fall-back solution was, with no teardown, was to pull the OP sender (or gauge line), if you have a PCV, unplug it, oil cap on, wrap a rag around the port, with an air nozzle apply some air pressure (you do not want to oil can the sump) while an assistant cranks it.

Air pressure pushed down on the oil, forcing it into the pickup in the sump, cranking keeps the pump from blocking flow, and open port allows it to vent. Without that open port, you're pressurizing a sealed vessel.

Try to get your mechanics to understand THAT.
That is a great idea, never heard that before!
Rut
 

64nailhead

Freshman Member
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I'll try the priming system described via the banjo fitting.

Does anyone have an oil flow diagram? And thanks greatly for all of the replies!!!
 

Joe Schlosser

Jedi Trainee
Silver
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Agree with everyone regarding priming the oil pump. If it has been sitting for a while it could have lost prime. This is pretty common. I use a oil can to push oil into the pump.
Also agree to check that the pressure relief valve is not stuck open.
Never heard if that method of pressurizing the sump, interesting method.
Sorry, cannot find an oil flow diagram in the shop manual.
 

TulsaFred

Jedi Warrior
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My shade tree rebuild of a 1275 gives me an initial oil pressure of close to 60, settling down to 25-30 once it warms up. I packed the oil pump with vaseline during assembly. Not sure a single engine means much, but that was my experience.
 

Rhodyspit75

Jedi Knight
Silver
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Priming the pump worked. Took about 20 seconds of cranking and oil pressure developed - 40 psi cranking. Thanks a bunch!!

You’re welcome. Thanks for letting us know that the procedure worked.
 

Rut

Obi Wan
Gold
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Congrats! Really happy to hear that it worked out and it’s a great feeling to see the op gauge rise. Firing that sucker up for break in will put a big smile on your face!
Rut
 

Dscarson

Freshman Member
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On the 948 engine there is an oil priming plug on the left side (facing the rear of the engine). Before mounting the carbs I fill that and have been successful at getting oil pressure on start up. It is hard to reach after the carbs have been mounted.
 

iceman

Freshman Member
Bronze
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You might see if any of your friends have a pressure system that goes between the oil filter and the copper line that runs from the passenger side of the engine. You pressurize a container that has oil in it and the oil under pressure circulates throughout the oil galleries without starting up the engine. The builder of my engine showed me how he hooked it up to my engine and it worked well. I am planning to make one to prime my next engine. Didn't look like it would be too difficult to make.
 
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