What should be my standard running oil pressure on a stock 2.8? When started, the needle reads around 20psi, but once it warms up it stays just above the red on the gauge. I get no oil warning light though.
When I start my 2.8 its around 65, after it warm's up it run's between 40-60. Some time's it will drop to 37 or so at idle when iv been driveing in stop an go an it's hot. But it go's back up as soon as I give it gas. I was told it sould run between 40-60.
I have a known good spare sender which I'll try. What should I do if the gauge is bad? I do have five quarts in it. Also, the engine sounds fine. No knocking or anything.
[This message has been edited by PatrickTRoof (edited 12-23-2013).]
The gauge should sit at about 0 with the ignition on but not running. Do as Larry suggested and check the hot oil pressure at idle speed with a mechanical gauge. Just remove the electric unit and screw it into the oil pressure tube. This will give you a reference point for your electric sending unit. While you're doing this, you may want to ground the base of the electric sender to keep your in-car gauge from pegging.
You can increase viscosity of your oil if you have higher mileage. If you're running 5 W 30, go up to !0 W 30 or 10 W 40 to increase your pressure.
Get yourself a good quality name brand electric sending unit. Shy away from Sorenson or BWD. Notoriously inaccurate even when new, but again, you can use the mechanical gauge reading as a reference point for any brand sending unit. Having said that, I just returned an AC Delco unit that had a solid ground at all times and would drain my battery in a couple of days if I didn't drive the car.
Your gauge and sender sound perfectly fine, they're operating just like they should. My guess is that your gauge needle is just reading off, like mine do, since so many of us have popped the needles off by now. Attach a mechanical gauge, verify good pressure, and reset the needle.
Now that I think about it, when I turn the key to "run" and the gauges zero out, I think the oil pressure needle dips below zero. I assume to reset it you just turn the needle on its spindle? I will still verify the pressure with a mechanical gauge.
I can't say for sure since mine are off haha, but if they're like every other GM just spin the needle counter-clockwise until it stops. Should be the same distance past the bottom of the gauge as the others. If not, force it further until it is.
But the reading on your gauge may not be based in reality. Screw in a mechanical gauge and read what it really is. Larry
What he said, I have a small plastic tool box with some of my test tools in it, a mechanical oil pressure gauge is one of those tools, just unscrew the sender and plug in the right one for a mechanical gauge, they are different, and make sure all the connections are tight. because oil does run threw those and you don't want a mess. That is really the only way to be sure you are getting a proper reading, besides just a little speck of dirt can affect an electrical sender, so when you change the sender you can check it for crap on it at the same time.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
I connected a mechanical oil pressure gauge to the sender port, and I'm running 55 psi cold. The needle on the stock gauge is in the correct position, so I either have a bad sender or a bad gauge, I suppose.
With the mechanical gauge installed, let the engine idle until the cooling fan kicks on, then see what the pressure reads. Don't base your diagnosis on cold pressure alone. Since the electric sending unit is a potentiometer, it could be good in one area and not in another.
Also, it may be worth noting that the stock gauge does read zero with the ignition on, and pegs when the sender is unplugged. And I have verified that the sender does turn on the fuel pump when air pressure is applied to it.
After warming up the engine to operating temperature and connecting the mechanical gauge, it reads 22.5 psi at idle, and easily jumps to 40 psi when the throttle is goosed. Reconnecting the electric sender, the needle stays just at the top of the red, and barely twitches when the throttle is pressed. I'm thinking I need to go get a quality sender and take it from there, or just leave the mechanical gauge connected and install it in the cabin!
Good. Pressure readings are very good. Now, you have reference points to use when you install the new electric sending unit. If it isn't near what your mechanical gauge read, return it. I've returned as many as 2 before getting a good one.
I had also searched for a T fitting to install both mechanical and electric sending units, but had a hard time. I eventually located one, but I don't remember if it was at Grainer, McNaughton-Mckay, or McMaster-Carr. You'll need one with 2 female and 1 male 1/4 NPT fittings.
The pegged needle will occur when the electric unit is plugged in, but the base not grounded. I try to avoid that by using a gator clip and lead to ground it before turning the ignition on. I don't want to take a chance of harming my gauge.
While most I've had trouble with were Taiwan-made BWD or Sorensen, I've had to return a new AC Delco to the Delco store, too. Made in Mexico. I also just returned an 88 AC Delco unit to Rock Auto. The circuitry was closed and put a constant 12V to ground. Drained my battery. They did replace it with another unit which seems OK when tested with a meter. It's made in Mexico, too. Just test it's accuracy against a mechanical gauge reading.
After warming up the engine to operating temperature and connecting the mechanical gauge, it reads 22.5 psi at idle, and easily jumps to 40 psi when the throttle is goosed.
Just for more accuracy, I'd go for a drive, then come back and check it. Operating temp on your temp guage is for the coolant. On my cars the oil pressure doesnt come down until about 20-25 minutes of driving, the oil warms up slower than the water.
Just for more accuracy, I'd go for a drive, then come back and check it. Operating temp on your temp guage is for the coolant. On my cars the oil pressure doesnt come down until about 20-25 minutes of driving, the oil warms up slower than the water.
That was after a drive around town. The only thing I can think of now is a wiring issue between the sender and the gauge. I am missing a ground strap, which is causing other problems.
These senders are pretty awful. But the ACDelcos I've had so far have been "good enough". They still die but when they're working their accuracy seems acceptable. I had BWD a few times but they were always reading too low when hot and sometimes made the warning light come on. I hated that.
You can use resistors to test the gauge. If I'm not mistaken it's a linear scale, 1ohm = 1psi. I know a 75ohm resistor will read just below 80. 82ohm should peg it at 80. You might prefer to check something lower in the range, like a 22ohm or whatever. If you have any serious thoughts about moving the needle, I'd check this first.
Here's how I got rid of the early style failure prone sending unit. You could install a 90 degree fitting into the pressure tube, making the sensor sit horizontally and this would reduce the possibility of water getting into the connection.
It's possible. The orange wire is constant 12 volt. When oil pressure builds in the sensor, it moves a contact on a potentiometer. The little rubber plug in the top of the sending unit was intended to relieve pressure inside the case, but also has the unintended effect of letting water get down into the inner workings, including the potentiometer. Corrosion is the result and corrosion reduces contact with the windings of the potentiometer.
Here's how I got rid of the early style failure prone sending unit. You could install a 90 degree fitting into the pressure tube, making the sensor sit horizontally and this would reduce the possibility of water getting into the connection.
Have you found the newer style to be any less failure prone? I did the conversion after getting the car a few years ago but I've kept on replacing it ever since. The one advantage I can say for the 88 style is at least it's smaller and easier to fit a socket over it.
I wonder if the real issue is exposure to water and maybe vibration. Without changing those things, it seems the reliability of the 2 sensor styles isn't any different.
I've only had mine in since the date on my link. Just a few weeks. Not long enough to determine if it's a better unit for the long run. I made the changeover based on the long-running thoughts on this and other Fiero furums that it is superior.
Based on it's style, I would think it's better because it eliminates the chance of water getting into the inside of the sender. BUT, I did find that water can run down inside the new style even though there's a WeatherPak seal on the harness. That's why I went to the effort to cover it with plastic wire loom and the reason for the suggestion of installing a 90 degree fitting in the sender tube. While I was waiting on Rock Auto to decide whether they would replace a defective unit, we had some rain. When I removed the unit to put the old style back in, I found the top was full of water. I expect this could cause a short between terminals, even in a good sending unit.
Here's the thing: now I don't know if it's a defective sender or if it's in the gauge or wiring. I didn't order an AC Delco sender...it's a Standard brand and its contacts look burned. I'm going to have to test everything this weekend.
Here's the thing: now I don't know if it's a defective sender or if it's in the gauge or wiring. I didn't order an AC Delco sender...it's a Standard brand and its contacts look burned. I'm going to have to test everything this weekend.
Update: I think the problem may lie in the gauge or wiring. Someone said that the center wire of the sender plug is constant 12v+. With the engine running and the sender unplugged, I put a voltmeter from the center pin to ground, and only got 7.xx volts.
Center isn't constant 12 V. The orange wire with tracer is constant 12 V. You can test that with your meter probe inserted into the harness.
Okay, help me out here. The wires are kind of faded and all look orange. The center wire is plain. The other two are orange, one with a white stripe and the other a black stripe. If I jump the two striped wires, the fuel pump comes on. I know the sender needs to be grounded to the engine to work. Where then does the center wire go? If I were to test the gauge with resistors, which lead do I want to use?
If you hold up the harness connector with the female terminals inside positioned like so I _ I , the blade on your left will be the hot terminal. Looking down at the sending unit with the blades sticking up and positioned as above, the blade on your right is the constant 12V. I believe the center is the gauge, the other is the fuel pump backup circuit. When I made my conversion to the 88 style, Boostdreamer or phonedawgz told me which was which. If you turn on the ignition, unplug the harness, your pressure gauge should peg past the 80 psi mark.
I verified my oil pressure with a mechanical gauge, verified 12v+ from the hot terminal, and verified the correct resistance from the gauge terminal on the sender with the engine running. All I can figure is the gauge is wrong.
[This message has been edited by PatrickTRoof (edited 02-25-2014).]
It could be that the gauge needle has slipped on the shaft from years of pegging at start up. It is entirely possible that your sending unit is bad right out of the box. If the needle sits on zero with ignition on but doesn't agree with the mechanical gauge, I'd say it's probably your sending unit.
The needle does zero out when the key is turned on, but does not peg at startup. I'm going to Radio Shack tomorrow and get some resistors to test the gauge.
I'm going to have to test everything this weekend.
