Oil Pressure - D1

[Siia109]

I searched for this on the forum and didn't really find a clear answer - at least for a knuckle dragger like me - I have the ultimate gauge plugged in and it is not picking up the oil pressure at all. I am learning how to use this but I am wondering if there even is a sensor that shows PSI readings or is it just a "dummy light" ?

Thanks

 

[Gordo]

To my knowledge it’s just a dummy light.

 

[LRDONE]

I searched for this on the forum and didn't really find a clear answer - at least for a knuckle dragger like me - I have the ultimate gauge plugged in and it is not picking up the oil pressure at all. I am learning how to use this but I am wondering if there even is a sensor that shows PSI readings or is it just a "dummy light" ?

Thanks

The switch opens at 7psi. I've bench tested two of them.

 

[Siia109]

Thank you both -
Can anyone direct me to how one would go about installing a sensor that would tell you the oil PSI in real time? With all the years this GM engine variant has been in use and the number of different cars its been installed in there must be something...

 

[94Disco1]

If you want to read oil pressure live you would need to install a pressure sensor either in one of the existing holes near the oil pump, or install a "sandwich" port between the pump cover and the oil filter. From there you run the wire coming from the sensor to a host of aftermarket gauge options (will need separate electrical connection behind dash).

I recently did a write up recently using the "fourby" clock (which monitors engine temp) and converted it to read oil pressure: https://landroverforums.com/forum/discovery-i-39/d1-fourby-clock-2-probes-question-116649/page2/

That effort was done to not have gaudy aftermarket gauges floating around the interior.

 

[Siia109]

If you want to read oil pressure live you would need to install a pressure sensor either in one of the existing holes near the oil pump, or install a "sandwich" port between the pump cover and the oil filter. From there you run the wire coming from the sensor to a host of aftermarket gauge options (will need separate electrical connection behind dash).

I recently did a write up recently using the "fourby" clock (which monitors engine temp) and converted it to read oil pressure: https://landroverforums.com/forum/discovery-i-39/d1-fourby-clock-2-probes-question-116649/page2/

That effort was done to not have gaudy aftermarket gauges floating around the interior.

Thanks -

 

[joeblack5]

94Disco1
Nice touch on the clock modification. Thanks for the link..
I am playing around with oil pressure sensors for my 1996 d1 3.9 serpentine belt and distributor.
The oil pressure cold 32 psi at idle is not close to fullscale on 80 psi dial so i .goong for an analog voltmeter and a 3 pin oil pressure sensor from a 99 jeep cherokee. At 0 psi it has 1 volt offset then linear to 3.5 volt at 50 psi.

So you have a graph of the temperature sensor / voltage input of the clock temperature module in the d1 ??

Another general question here is how the oil flows from the pump? I used the oil port for the idiot light.
This seems to be the oil gallery. So after the pump, oil cooler, filter and bypass valve.
Any idea where the relief valve is ? After the oil pump, after the cooler or after the filter? See my struggles in my member trucks thread.

Thank Johan

 

[boxster]

 

[boxster]

A couple of pics of the oil gallery LR V8. On the front cover next to the return oil line there’s internal C clip which holds the pressure relief valve piston. Chased a oil leak and found the Oring on the piston failed FYI.

 

[boxster]

 

[boxster]

A better image of relief port to left of the oil return line.

 

[94Disco1]

94Disco1
Nice touch on the clock modification. Thanks for the link..
I am playing around with oil pressure sensors for my 1996 d1 3.9 serpentine belt and distributor.
The oil pressure cold 32 psi at idle is not close to fullscale on 80 psi dial so i .goong for an analog voltmeter and a 3 pin oil pressure sensor from a 99 jeep cherokee. At 0 psi it has 1 volt offset then linear to 3.5 volt at 50 psi.

So you have a graph of the temperature sensor / voltage input of the clock temperature module in the d1 ??

Another general question here is how the oil flows from the pump? I used the oil port for the idiot light.
This seems to be the oil gallery. So after the pump, oil cooler, filter and bypass valve.
Any idea where the relief valve is ? After the oil pump, after the cooler or after the filter? See my struggles in my member trucks thread.

Thank Johan

Yeah - it is slightly more complicated though. The aftermarket sensor has a resistance/voltage curve that correlates to pressure. The clock display reads in resistance (from what it thinks is a thermistor) but instead the Arduino drives a chip that provides an artificial resistance correlated to the pressure. So the clock displays what it thinks is temperature based on resistance, but instead it is fed resistance that correlated to the pressure received from the oil pressure sensor. Couple of constants/fudge factors in there as well. Happy to send you the excel math model + arduino code + circuit diagrams. Just DM me.

 

[joeblack5]

Thank you boxter,

Yes that is the cover I have, and I hooked the oil pressure gauge as shown.. I guess they do not show the allen head bolt that is in the way of a socket to get the sensor out.

This is a pic I gleaned from the web..

Are the two threaded studs on the bottom where the oil intake with strainer attaches to?

Then it seems that the oil relief valve is in the gallery above where the oil returns from the oil cooler, so restrictions in filter and oil cooler would not affect the pressure.

What is the lower oil gallery doing. The oil comes out at the bottom towards the cooler but it seems to continue also to the filter, is there a secret bypass valve?

My pressure is 32 psi cold idle and does not increase with higher rpm. It actually drops 1-2 psi with higher rpm??

That it does not increase means that my relief valve spring is weak?

I feel that the metal oil cooler pipe is pretty small diameter for a large flow.

And then there is this...d2 oil relief.pdf, also gleaned from the web.. this has the oil filter straight down... it describes a relief valve on the right and a bypass valve on the left.. does the d1 not have a bypass valve and so why not or why does tye d2 need one. Also where the d1 has the relief valve, the d2 has the bypass valve ( oil filter restriction) the d2 has the relief valve on the driver side.

Or am I confused and is the relief valve in the d1 actually a bypass valve.

Ha,

Johan

Johan

 

[boxster]

The 2 threaded studs is part the front cover which holds the oil pan in place. Yes to your second question, oil pump draws the oil up thru the pickup screen tube out to the oil cooler then to the oil filter where it pressurizes the gallery to the oil pressure switch and flows into the crank, cam and valve train oil galleries.

 

[boxster]

Relief valve is designed to limit the pressure in the system. Bypass valve is used to redirect the flow in the system.

 

[joeblack5]

Thank you Boxter, I am aware, I am looking for very specific info. The documentation of the oil system for the 3.9 daco is lacking.
Having read most threads about the oil system on this site and other lr sites shows no answers to my questions.

-Is the oil pressure relief valve prior to the oil cooler and filter or after it.

Thanks Johan .

 

[LRDONE]

It's built into the housing right next to the pump. The relief doesn't intercept any certain line but opens up based on entire system pressure. So you can say it's before or after everything else in the system, it doesn't matter. It's designed to relieve system pressure based on a restriction anywhere in the system. It's sort of an irrelevant thing to know. Based on your original question, Where the original oil pressure sensor sits, this is the last point the oil flows through before it enters the motor. If you're going to install any aftermarket sensor, figure out how to do it there. Then you know nothing outside of the motor is restricted and the inside of the motor is creating pressure. I went down the rabbit hole of wanting to put a better sensor on mine but then I remembered that oil pressure is oil pressure and if my light isn't on and the motor isn't knocking, I'm not worrying about it.

 

[boxster]

Thank you Boxter, I am aware, I am looking for very specific info. The documentation of the oil system for the 3.9 daco is lacking.
Having read most threads about the oil system on this site and other lr sites shows no answers to my questions.

-Is the oil pressure relief valve prior to the oil cooler and filter or after it.

Thanks Johan .

According to the flow diagram it’s after the oil cooler.

 

[joeblack5]

Ok , thank you both, boxter, that would make sense but I cannot see it in the picture, then in the casting picture it looks like there are oil galleries that connect directly to the output of the pump. So that would indicate the opposite.

Lrdone, it makes a big difference.. if you relief the pressure before the oil filter then with cold oil and a dirty filter the main amount of oil would flow back to the pump inlet and very little oil would make it thru the filter to the bearings. Result would be low oil pressure. This design would protect the oil pump ,oil cooler and filter.
If you have the relief valve after the filter then the pump will build very high pressure to push thick oil thru a clogged filter and more pressure would remain for the bearings.
This design would insure oil at the bearings but could damage the pump and filter if an oil bypass valve in the filter is to high or absent.
I guess an issue because tye d2 has a bypass valve as well .
So the actual situation is very relevant in trouble shooting.

As already stated I take oil pressure at the location of the sensor . Pressure is 32 cold and drops 2 psi when revved up.

Johan

 

[Greg_M]

I feel that the metal oil cooler pipe is pretty small diameter for a large flow.

For a given volume, large flow = low pressure. Pressure depends on restriction.