Oil Pressure

[pezzonovante88]

What should the oil pressure gauge read while cruising?

Edit: Original oil pressure sender.

[Jonathan]

If you've got the original oil pressure sender, than in all likelihood it will be pegged high when you're cruising.

If it's been replaced with the new and improved/calibrated one, it will likely hover about 3/4's of the way up the scale when you're cruising along at highways speeds.

And, if you've got that new style one (and it's believed to be more accurate), the experience I have with mine is that if you're sitting idling at 775 RPM, the oil pressure will drop down to say 1/3 the way up the scale. Lower RPM's = lower oil pressure. ---> EDIT: on second thought, ignore this. I was thinking more when on some rare occasions where the idle is too low does it go to a low point on the oil pressure gauge.

Check this link out and you can see my oil pressure gauge:


http://www.youtube.com/watch?v=EPhH_NowHh8&feature=relmfu

I think there may be a way to tell looking at your sending unit from the outside/while it's installed, but I don't know off hand what that is... maybe someone else will chime in?

[DMCMW Dave]

I think there may be a way to tell looking at your sending unit from the outside/while it's installed, but I don't know off hand what that is... maybe someone else will chime in?

The original sender is marked with an AC (as in "AC Delco"), and the wire connection is a nut/lug setup off-center. The replacement one we sell is a nut/lug that is centered, and there are others that use a spade lug.

[pezzonovante88]

If you've got the original oil pressure sender, than in all likelihood it will be pegged high when you're cruising.

If it's been replaced with the new and improved/calibrated one, it will likely hover about 3/4's of the way up the scale when you're cruising along at highways speeds.

And, if you've got that new style one (and it's believed to be more accurate), the experience I have with mine is that if you're sitting idling at 775 RPM, the oil pressure will drop down to say 1/3 the way up the scale. Lower RPM's = lower oil pressure. ---> EDIT: on second thought, ignore this. I was thinking more when on some rare occasions where the idle is too low does it go to a low point on the oil pressure gauge.

Check this link out and you can see my oil pressure gauge:


I think there may be a way to tell looking at your sending unit from the outside/while it's installed, but I don't know off hand what that is... maybe someone else will chime in?

My oil pressure gauge reads about that when cruising, maybe a bit higher. I cant really tell at idle because it rev hunts like crazy. Anyway, thanks.

[LordFly]

Sorry to bring up a dead thread, but it is it's 1 year anniversary ;)

My gauge is pegged high at all times, even when the car is off. Bad sender, or bad gauge?

[David T]

Could be either. Take the wire off the sender and see if it affects the gauge. As a FYI a general rule-of-thumb oil pressure should never be less than 10 psi at idle and for every increase of 1,000 RPM the oil pressure should increase 10 psi so for example at 2,000 RPM's the pressure should be at least 30 psi. Measure with a known, accurate mechanical pressure gauge.
David Teitelbaum

[Jonathan]

Sorry to bring up a dead thread, but it is it's 1 year anniversary ;)

My gauge is pegged high at all times, even when the car is off. Bad sender, or bad gauge?

Devon, just to clarify, it is your oil pressure gauge pointing straight up, or the fuel gauge?

[DMCMW Dave]

Could be either. Take the wire off the sender and see if it affects the gauge.

Then run a clip-lead from the sender to ground. That should make it read less than zero.

[LordFly]

Devon, just to clarify, it is your oil pressure gauge pointing straight up, or the fuel gauge?

I wish my fuel gauge was pointing up ;)


Then run a clip-lead from the sender to ground. That should make it read less than zero.

Perfect, will try to get to this tonight see see if it helps. Geez, only had the car for a week and a half and the binicle will be out for the second time!

[Jonathan]

No worries on the fuel gauge.

You mentioned the oil gauge being pegged full at all times even when the car is off. The fuel gauge thought came from the difference between the needle pointing straight up at 12 o'clock and it pointing at full around 1 o'clock or so. 12:00 often tells you it's an electrical problem of some sort, 1:00 says something else.

On the oil gauge, pegged full could be telling you your car has the old style sender. Replacements let the needle display in the middle of the gauge because the calibration was better. Old senders pegged the needle most of the time.

Some of the gauges keep the needles where they were when you shut the car off and others don't. Temp and oil stay where they were for example and the tach does something else bizarre entirely. If you have the car off and put the key in and turn to accessories, does the needle go back to zero? And when the engine starts it goes back to full? Watch my video a few posts back to see what I mean.

In your "how does it look" thread photos, your needle is at about 3/4. Do you think something got messed up while you had the binnacle out the first time?

[LordFly]

Upon closer inspection, it does move, just not very much. 3 pictures below show key off, key on, engine running. I would say bad ground, but normally (on other cars) the sending unit would be grounded through the engine.

178241782517826

[LordFly]

With the wire removed from the sending unit and clipped to ground, I get 0 with the key on. I cleaned up the connection really well and hooked it back up, but still reading off the scale.

17828

[LordFly]

Sorry, but I'm going to veer slightly OT for a minute

I know yours is a metric Canadian car, but still - I have never seen pressure shown as kg/sqcm

I know it is just a metric conversion of psi, but I work in a continuous process industry and I thought I had seen them all - psi, inWG, inHg, mmHg, Pa, bar, mbar.

Is this an 80s thing? What units do contemporary Canadian cars use, those that even have pressure indicated.

I couldn't tell you really, I haven't seen a modern car that showed oil pressure. But then again, I rarely get the opportunity to drive anything modern. It's definitely one of the more arbitrary units of measurement I've seen displayed in a car. PSI would be preferable, but I guess this was the most metric unit they could think of ;)

[LordFly]

Devon, can you take a picture of your full instrument cluster? I too am curious as to the differences between the American and Canadian types.

Happily, but I think engine temp in °C is probably the only other difference. Also, my tach does not spike up to 5000 when I shut the car off, it drifts up there slowly, probably over the coarse of 3 - 5 seconds. But we're getting a little off topic from my oil pressure gauge issue.... Bad sending unit? I'd hate to order one if I don't need it.

17850

This is engine off, key off. I am not revving the piss out of it in the garage ;)

[Ron]

Splits:

Temp Gauge Jumping Here (http://dmctalk.org/showthread.php?6709-My-temp-gauge-jumps-violently-***SPLIT-From-Oil-Pressure***)

Tachometer (http://dmctalk.org/showthread.php?6710-Tachometer-***SPLIT-FROM-OIL-PRESSURE***)

Metric Gauge Conversions (http://dmctalk.org/showthread.php?6711-Metric-Conversions-On-Gauges-***SPLIT-FROM-OIL-PRESSURE***)

[LordFly]

Glad that one got split, we're so off topic I almost forgot what the problem was ;)

So oil pressure sending unit.... anyone have electrical diagram of it? I assume it is just a variable resistor that varies with pressure, but I'm often wrong when it comes to this car.

[Ron]

Glad that one got split, we're so off topic I almost forgot what the problem was ;)

So oil pressure sending unit.... anyone have electrical diagram of it? I assume it is just a variable resistor that varies with pressure, but I'm often wrong when it comes to this car.

LMAO...and I was answering you in yet another split...hold on before I screw something up.....

OK, If the gauge goes from ~max high to ~max low when the key is on and you remove the sender wire and ground it, the gauge and wiring is probably good and the sender is probably bad.
(You really don't have to remove the sender wire to do the test (grounded is grounded).

[LordFly]

LMAO...and I was answering you in yet another split...hold on before I screw something up.....

OK, If the gauge goes from ~max high to ~max low when the key is on and you remove the sender wire and ground it, the gauge and wiring is probably good and the sender is probably bad.
(You really don't have to remove the sender wire to do the test (grounded is grounded).

Haha, hope I'm not messing the place up too badly ;)

Ok, that's kinda what I figured. I wasn't sure how the sender worked, so I didn't want to ground the signal wire while still attached to the sender. If the sender was spitting out voltage (which I'm fairly certain it's not), jumping it to ground would likely fry something. Or at least blow a fuse somewhere. I'll add oil sender to my giant DMC wishlist. Thanks :)

[Ron]

NO..it wasn't you (ahemmm ;-)

And you got the circuit right...the sender varies the ground to the block.
Lots of electrical schematics HERE (http://dmctalk.org/showthread.php?40-All-Wiring-Schematics/page2) in the Resources Section

Yeah I'd get one, as said, the old style was crap anyway lol

[LordFly]

I took a look through that thread, but couldn't find one for oil pressure sender or gauge.

According to This Thread (http://dmctalk.org/showthread.php?932-Parts-Crossover-List):


Oil Pressure Sender:

AutoZone Part #PS133 (75-81 Corvette unit)

Is that a decent replacement, or stick with DMC stuff?

[mluder]

Yep... Sorry.

I single handed split this thread into three.
Although to be fair we were still discussing the effects of a bad ground at the instrument cluster which was part of the initial discussion.

I'm going to go play in my threads now...

Cheers
Steven

[mluder]

Then run a clip-lead from the sender to ground. That should make it read less than zero.

Dave,

My car just did this - Oil Pres Guage pointing stright up. I recently replaced it with the Auto Zone part and it was working great. I've been having issue with my DMC alternator and in the process of removing it for testing I disconnected the lead from the pressure sender.

After testing, I reconnected the alt and the pressure sender and now it reads stright up.

I disconnected the clip lead and ran the wire to ground (which is what I think you meant - run the wire to ground not the sender unit) and it droppeed to zero.

So... I need to replace the sender again?

Cheers
Steve