Just to clarify, was there oil in the filter when you removed it? If there was, the pump must be working.
GM 5.3: No oil pressure after oil change
- Thread starter HawkeyeScott
- Start date
Thanks for the input.
Any idea how long I can run it as I diagnose and test? Like I said, watching it run for about 7 seconds gave me chest pains. 10 seconds? 15? 30?
Also, if it is pumping and oil is moving around, the dipstick should have oil on it well above the fill line, right? That will be one diagnostic point when I get home tonight.
Thanks again. This is stressful for a BITOGer!
Any idea how long I can run it as I diagnose and test? Like I said, watching it run for about 7 seconds gave me chest pains. 10 seconds? 15? 30?
Also, if it is pumping and oil is moving around, the dipstick should have oil on it well above the fill line, right? That will be one diagnostic point when I get home tonight.
Thanks again. This is stressful for a BITOGer!
Yes but in the vast majority of cases, it will still show pressure.
I thought SBC oil pressure sensors failed at full pressure - meaning when they fail, they peg the gauge to max pressure.
They usually internally short, 5 volt reference shorted to the signal circuit which the ECM interprets as @ 140 PSI, The ECM knows this is implausible, So it sets a DTC for the EOP sensor circuit & the Cluster will command the pressure gauge to zero.
This must have changed for the 07+ ECM's? Mine just stays at max oil pressure on the gauge and 135 on torque pro. No code set either.
Correct, Of coarse the GMT800 can be split in 2 different era's.....'99-'02 used a single wire resistive EOP that was wired directly to the cluster, '03-'07 used a 3 wire digital EOP wired to the ECM then the pressure reading was sent to the cluster via Class 2 serial data.
GMT900's works the same way as the late GMT800's but with diagnostic & sanity checks.
To close the loop on this: I checked the dipstick after running. It did not show any oil splash above the bottom section that sits in the pan. This told me oil was not moving around the way it normally does. So I used the LS/weed sprayer method (YouTube) to pump oil into the side of the block after removing the galley plug on the left front of the motor. Then, when I went to start it, the truck didn't turn over because the 6 year old battery had finally died.
Upon install of the new battery, the oil pressure gauge jumped to 80 PSI before I even started it. Then, it crashed to 0. Once I started it, it remained on 0. However, pulling the dipstick showed oil splash up higher at the normal levels. That told me the pump was primed and pumping. I then took out the oil pressure sensor and replaced it. The screen was spotless. Now I have oil pressure at the gauge.
Not sure I understand it all. Definitely seems like there were two issues: pump prime and then the sensor failure. Throw in the dying battery and I don't know why. But that's what appears to have fixed it all.
Upon install of the new battery, the oil pressure gauge jumped to 80 PSI before I even started it. Then, it crashed to 0. Once I started it, it remained on 0. However, pulling the dipstick showed oil splash up higher at the normal levels. That told me the pump was primed and pumping. I then took out the oil pressure sensor and replaced it. The screen was spotless. Now I have oil pressure at the gauge.
Not sure I understand it all. Definitely seems like there were two issues: pump prime and then the sensor failure. Throw in the dying battery and I don't know why. But that's what appears to have fixed it all.
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Glad you got it rolling again!
CleanSump
Site Donor 2022
Thank you for the follow-up/case closure. It could help someone else.
Everyone should follow your example. Ghosting without revealing the results is kind of disrespectful to those who helped and no use at all to anyone else.
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