zero oil pressure help
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Joined: Jun 2007
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From: Middletown nj
zero oil pressure help
hi i just bought my first c5. its a 2000 frc.well on my way home from getting the car about to pull in my driveway the oil pressure gauge droped to zero and dic said oil pressure xxx and service engine soon.anyone have any ideas what it could be.i had 40psi of pressure all the way home. im hoping its a connection or senor anyone else have this problem.i really upset because i just bought the car and i hope its something stupid
Le Mans Master
Joined: Jul 2002
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From: Slave to the evil empire
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St. Jude Donor '04
When the sensor fails it generally fails indicating pegged out oil pressure, I don't think I've ever heard of one failing and showing "0" pressure.
You may have to hook up a gauge to an oil port to manually measure the pressure. This can be done one of two ways, either hooking into where the oil pressure sensor is behind the intake manifold or tapping into the oil gallery on the lower left side of the block. If you look at the side of the block below the alternator you should be able to see the plug.
You may have to hook up a gauge to an oil port to manually measure the pressure. This can be done one of two ways, either hooking into where the oil pressure sensor is behind the intake manifold or tapping into the oil gallery on the lower left side of the block. If you look at the side of the block below the alternator you should be able to see the plug.
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Im well aquainted with a ZERO oil pressure issue.
When I did my heads, cam, FAST 90/90 install, I had ZERO pressure indications on first start!
. I didnt have any unusual noises. I let it run for 30 sec and shut her down.
The BEST way to figure out if you really have pressure is to remove the oil galley plug at the front drivers side of the engine. Its on the BLOCK below the alternator. Install a mechanical gage. and start it up. If you have pressure, it will show there. That port is directly off the pump. I had plenty of pressure at that port!
My issue was; I installed a MAP sensor relocation kit and extension harness and the extension harness was able to be plugged in either way. Unfortunatly I had mine reversed and that caused the 5 VDC sensor reff voltage to ground out. Once I figured out that I had pressure, I used a volt meter to read the 5 VDC reff signal on various sensors. There wasnt any present.
Then I saw that the connector wires didnt match up to the color wires on the MAP connector at the rear of the engine. 
I also removed the oil filter and was able to see that the oil pump was pumping vast quanties of clean oil.
The oil comes out of the center nipple that the oil filter screws on to.
So now you have a few places to start troubleshooting.
BC
When I did my heads, cam, FAST 90/90 install, I had ZERO pressure indications on first start!. I didnt have any unusual noises. I let it run for 30 sec and shut her down.The BEST way to figure out if you really have pressure is to remove the oil galley plug at the front drivers side of the engine. Its on the BLOCK below the alternator. Install a mechanical gage. and start it up. If you have pressure, it will show there. That port is directly off the pump. I had plenty of pressure at that port!
My issue was; I installed a MAP sensor relocation kit and extension harness and the extension harness was able to be plugged in either way. Unfortunatly I had mine reversed and that caused the 5 VDC sensor reff voltage to ground out. Once I figured out that I had pressure, I used a volt meter to read the 5 VDC reff signal on various sensors. There wasnt any present.
Then I saw that the connector wires didnt match up to the color wires on the MAP connector at the rear of the engine. I also removed the oil filter and was able to see that the oil pump was pumping vast quanties of clean oil.
The oil comes out of the center nipple that the oil filter screws on to. So now you have a few places to start troubleshooting.
BC
Tech Contributor
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From: Van Buren Arkansas
Wounded Warrior Escort '11
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Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Pumps can fail. Usually the pump doesnt fail but the reliefe valve inside the pump gets stuck OPEN and you have NO pressure. If you install that mechanical gage in the forward port, you can remove all the spark plugs and use the starter to CRANK the engine over to test for oil pressure. Pressure comes up VERY QUICKLY if the pump is good. I saw 45 PSI in about 4-5 engine revolutions.
That will put the least amount of stress on the engine and still give you the info that you need.
Thats my recommendations. I second guessed my mechanical abilities and the FIRST thing that I did was rip the old pump back out and install a new melling pump. I did take the old pump apart and there wasnt anything wrong with it or the new O ring that I installed!
That mechanical oil gage check is you best bet!
Thanks guys for the vote of confidence.
That will put the least amount of stress on the engine and still give you the info that you need.
Thats my recommendations. I second guessed my mechanical abilities and the FIRST thing that I did was rip the old pump back out and install a new melling pump.
I did take the old pump apart and there wasnt anything wrong with it or the new O ring that I installed!That mechanical oil gage check is you best bet!
Thanks guys for the vote of confidence.
Le Mans Master
Joined: Jul 2002
Posts: 7,370
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From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
The C5 is one of the easiest cars I've worked on next to the 79 Camaro or 79 Trans Am, or were these the F-bodies that you were talking about.
my sender went bad on mine after my heads/cam/bolt-ons install. i was worried too but it was weird so i searched and found it's common. changed it, works great
Le Mans Master
Joined: Feb 2002
Posts: 6,937
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From: Waldorf MD
I have seen a few of these no pressure sensor failures now. Not common, but it does happen and is terrible (stressful) to diagnose ! Easiest way is to start-up and listen for ticking noise, but I can understand some people not wanting to do this.
Now if you have replaced oil pump, that o-ring mis-install (cut or not in groove) is always a prime candidate.
Now if you have replaced oil pump, that o-ring mis-install (cut or not in groove) is always a prime candidate.
Last edited by Oldvetter; Jan 31, 2009 at 09:26 AM.
