Oil Pressure Gauge Help???

[KBMWRS]

The particulars:
1967 Ford Mustang
390ci

Instrument panel has Tach with clock in upper center gauge location (non-working).
Currently an oil idiot light is located within the Tach (lower left location)

What I wanted to do: remove clock and install a stock oil pressure gauge in its place.

Craig gives me a working Oil Pressure Gauge (OPG) that would be a natural fit in the clock location.
Oil sensor (button like sensor, coarse thread) is located on the top of the oil filter housing.

UNDER-HOOD
1: remove WHITE with RED stripe wire attached to threaded top of button style oil sensor (90degree connector).
2: remove button style oil sensor
3: install Oil Sensor for oil pressure gauge equipped cars (canister type with coarse thread attachment and small threaded post at the top.
4: re-attach WHITE with RED stripe wire to top of small threaded post atop oil sensor.

INSTRUMENT PANEL
After removal of panel to gain access to gauges.

1: detach wiring to clock, Remove clock
2: install OPG in its location (adapted a mounting system that hold gauge in place, made of plastic)
3: cut WHITE with RED wire going to Oil idiot light and attach to right post (as looking down from above) of the OPG
4: Tap off of the constant voltage regulator (using spade connectors) on back of speedo (for power) and attach this wire to left post (as looking down from above) of OPG.

Problem:
Upon moving starter switch to ON or STARTING engine, OPG does not move.
OPG can be grounded separately and the needle will swing fully, so OPG works.

I have been through 3 Oil Sensor switches (canister types). All the same outcome.
I have been told that these sensors should have a ohm resistance of 20-80ohms.
Is this with the engine running and the sensor in its place?

I even tried running a wire directly from the top post of the oil sensor to the right post of the OPG (by-passing any old car wire problems) and still no movement of the OPG.

Is there something special about a 390 oil sensor that I'm missing?
Thanks for any help.

 

[Midlife]

I'm out of ideas, Mike. The best one I had was that the plug for the oil/temp/coil was bad (about 40-50% are bad in 67/68's), and that the higher resistance fails to give you the reading you're looking for.

Very very strange.

Can I suggest you go back to the idiot light configuration and see if that still works correctly?

 

[KBMWRS]

So put the White/red wire back on the oil light and then ground the white/red wire that would usually attach to the oil sensor?

The light would glow then correct?

 

[AzPete]

It should.............

 

[cmayna]

But since Mike eliminated any of the car's existing wiring by using a bypass wire, what good is testing the idiot light setup?
I will say, the only thing that has been used in all attempts is his CVR.


Nevertheless, I just finished simulating an oil pressure sending unit test by applying approx 60 PSI of air to the inlet port of the sending unit and got about 60 ohms :thu With the sending unit test successful, I'm going to simulate a complete oil pressure gauge test using Shag's original water temp gauge, cluster, cvr, etc. If I can get the water temp gauge to fire up then I might consider swapping the guts of it with the oil pressure gauge that Mike has, unless a better idea comes along.

 

[KBMWRS]

What about Randy's comment about defective senders?

Could I have had 3 in a row?

Should I try the 4th?
The cheaper NAPA version?...both boxes say 'made in mexico'

I just read that write-up in response to your post in the instrument forum. Seems like we're all good...except that the dang thing doesn't work.

I notice it said a cold engine would keep the needle to the left.....but shouldn't we expect some type of jump from far left to maybe left side of the marker on the gauge when ignition or even the engine fires up?

 

[cmayna]

Cold motor, meaning not running then yes, the needle would remain left, but as soon as oil pressure built up right after startup, the needle should move. I'm going to Kragen's today and pick up another sending unit to do my bench test since I cannot use my spare because it is designed for my auto meter gauges. Yes, I will keep the receipt with plans on returning it.

 

[Midlife]

Two other things might be happening:
(1) No oil in the motor. Not Likely.
(2) The bypass valve in the oil filter is not allowing oil to go into the oil filter and then to the sending unit. This has happened before and is possible. I would recommend unscrewing the oil filter, then starting the engine to see if any oil comes out....tee hee.

 

[KBMWRS]

Took the oil pan off....yep there's oil. :roll :roll :wth

 

[cmayna]

Mad scientist here

I was able to simulate the oil pressure sending unit activating the water temp gauge using a 12v source to feed the CVR. With a hose between the the sending unit and a regulated 60psi I was able to move the needle halfway.

Amen


TapaYakin' from my iPhone

 

[Midlife]

OK...that means that everything is working from the sending unit all the way to the gauge. The only part of the system that hasn't been checked is whether there actually is oil pressure at the OSU.

That's one reason why hooking up the old oil indicator light would be instructive. If no oil is getting to the OSU, then the light should go on and stay on with the engine running.

Another test is to use a proper fitting and run a see-through hose to a small fixed container and start the engine. The oil should run up through the hose, compressing the air that is in the system. My bet is that for whatever reason, no oil is getting to the sending unit port.

 

[cmayna]

Sir Randall, Mike said that he did not change the oil or filter right prior to this project. So if something is blocking the oil from getting to the sending unit then something must have fallen down into the hole and is sitting there being slammed back up against the port of the sending unit.

Now, remember I just tested my water temp gauge today. The only test we have done to the actual oil pressure gauge is the ground test having it peg out. I'm planning to obtain Mike's complete instrumentation with the oil pressure gauge attached and do another test like I did with the compressed air.

 

[Lemondrop]

Did you use teflon tape on the sensor threads?

The sensor may not be grounding to the engine thanks to teflon tape. Try clipping a ground onto the case of the sensor and then attaching it to a good known chassis ground.


Edit to add:
Take the wire off the oil P sensor and touch it to the can of the sensor and see if the gauge moves. If it does your ground is OK. If not, you have no ground on the oil pressure sensor.