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motor replacement- no oil pressure


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I have a 1997 sts with a 4.6l in it. I recently repaced my motor with a remanufactured one. I am getting a low oil pressure indication with the bell. I put a guage where the sensor is and it is reading 9 psi at idle and more above that. I have replaced the sensor twice from the GM dealer and still the indication. The motor is not tapping, and oil can be seen flowing through the lifters when you open the oil fill cap.

Is there anything else that could cause this indication?

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I am not sure what the spec is for oil pressure at idle on the 97.

If you are getting a correct low oil pressure reading, perhaps the pickup for the oil pump is off, or clogged? I'll defer to others as to whether this can be diagnosed or remedied with the oil pan off?

Bruce

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I have a 1997 sts with a 4.6l in it. I recently repaced my motor with a remanufactured one. I am getting a low oil pressure indication with the bell. I put a guage where the sensor is and it is reading 9 psi at idle and more above that. I have replaced the sensor twice from the GM dealer and still the indication. The motor is not tapping, and oil can be seen flowing through the lifters when you open the oil fill cap.

Is there anything else that could cause this indication?

The statement that I bolded above is VAGUE..... Explain what you mean by MORE above that, what does the pressure increase to?

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It looks like Scotty is focusing on things. If you guys agree that the oil pressure is OK, then the sensor wiring isn't complete, and perhaps you should go back to the installer with the wiring problem. This should be a minor issue for the installer if that is all that is wrong. If Scotty tells you that the oil pressure is low, then, of course, you have an issue with the remanufacturer.

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I seem to recall our old Guru saying that the Northstar will idle at about 5 psi and that 5 psi is plenty. What kind of oil pressure are you getting above idle?

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I seem to recall our old Guru saying that the Northstar will idle at about 5 psi and that 5 psi is plenty. What kind of oil pressure are you getting above idle?

I am not sure what Jim means with the "Scotty is focusing on things" statement above, Ranger, but your statement was exactly what I was thinking. The original poster left a HUGE piece of information out of the equation, what is the oil pressure rising to?, we could not make an intelligent statement WITHOUT that info.... I tend to NOT give my opinion without all of the facts, its a waste of time for us all.

If this guys pressure is rising to a normal level above idle, the 9 PSI at idle is normal for the NS. Then its in the connection or wiring, in that a bad signal is being sent to the computer since he replaced the sensor already.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Regardless of the oil pressure ABOVE idle, the oil pressure sensor, which is really a switch, is calibrated to about 4-5 psi of oil pressure. That's the spec for the Northstar engine. As long as it's idling above 5 psi, there's sufficient pressure TO NOT SET OFF THE SWITCH. As long as the pressure can be verified above 5 psi at idle, and the switch has been replaced, the problem has to be in the wiring as Jim (and BBF) suggested earlier.

Edit: let me word it a different way. The bell will chime when the PCM thinks the engine has less than 5 psi. Regardless of engine RPM or anything like that. The oil pressure at 2000 rpm or some other rpm isn't relevant to this discussion. The system checks for 5 psi. As long as there's 5+ psi at idle, and the oil pressure only goes up from there, that's really all we need to know I believe. Obviously the PCM still thinks the engine has less than 5 psi of oil pressure. If the switch has already been replaced, you must look at why the computer still thinks the engine has low oil pressure. The next most likely cause is the switch wiring.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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  • 3 weeks later...

Thanks guys for all the help.

I reinstalled the conector plug to the sensor and the problem went away. 55psi for the oil pressure when racing the engine. Now all the bozo garage needs to do is tighten all of the motor mounts and after 3 months Ill be able to drive the car.

Dont ever use a garage that has not worked on the northstar motor. Hard lesson learned.

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