Weird oil pressure problem

[kikkegek]

he guys,

need some help.

My oil pressure went from 0 to 15 psi as soon as I started the engine and then sticks there no mather what the rpms are. strange!

So i read some on the forum and did some research:

- connected the wire from the sender to the guage to the ground and checked what the gauge shows: MAX out...so guage should be fine

- I checked the oil pressure with a mechanical guage. result was about 15 psi at idle and about 40-45 psi at 3000-4000rpm...so fine too for a 25 year old engine.

I then figured it could only be the sender. So I replaced the sender.

Now the guage is showing even less...when I start her up, the guage shows about 10 psi and again doesnt move when revving...

what is going on? any ideas?

[Your41Plague12]

I had a similar problem once, and the parts guy at the store gave me a sender for a truck with idiot lights, not gauges. Take it back and make sure the one you have is for gauges, not idiot lights.

[J Knight]

Originally Posted by Your41Plague12

I had a similar problem once, and the parts guy at the store gave me a sender for a truck with idiot lights, not gauges. Take it back and make sure the one you have is for gauges, not idiot lights.

X2 Makes total sence, idiot light sender only needs to detect pressure, not how much.

[Your41Plague12]

Mine just happened to read above 60PSI all the time, and I thought I just had insane oil pressure for a while . When I got the correct sender, it went down to about 35-40 at idle and went up from there. It'll go up to 60 no problem when romping on it.

[kikkegek]

I checked the type and I got this one:
http://www.summitracing.com/parts/SMP-PS154/



Part specifications:

Description	                        Value
Connector Gender  	        Male
Maximum Vehicle Quantity	1
Number of Terminals	        1
Operating Pressure - PSI	0-10 psi, 0-27 Ohms, 60 psi, 65-90 Ohms
Terminal Gender	                Male
Terminal Type	                Blade
Thread Size - NPT	        1/8" - 27 Thread

[Your41Plague12]

That looks like the correct one, but I'm not sure about the 0-10 psi part in the description. Maybe someone can shine some light on this for you. I know that looks like the correct one in the picture.

[BrookelynnGreen]

My 86' C-10 has an "after market" electric & oil psi gauge, and mine is at 0 when the truck is off, and when i start the truck it goes to 15, and when i drive it goes to around 20. I just bought the truck like that and i too was worried about low oil pressure. i just think its the "stupid" people who hacked my electrical system, and now im trying to fix all thier mistakes!!

[kikkegek]

did some more research today. I measured the old pressure sender and it shows 20 Ohms while it should be reading 0 Ohm. That explains the 15 PSI I had in the car all the time. that one is for sure broken.

I am taking the new one out of the car tomorrow and checking if it really measures 0 Ohm when not in the car. Forgot that.

I also found a 30 Ohm resistor in my stuff. While I am at it, I will connect that to the wire from the sender and ground it, so I can see if my guage will show about 10 PSI.

I'll be back...hope I can solve this soon...

[kikkegek]

did some more research today. I measured the old pressure sender and it shows 20 Ohms while it should be reading 0 Ohm. That explains the 15 PSI I had in the car all the time. that one is for sure broken.

I am taking the new one out of the car tomorrow and checking if it really measures 0 Ohm when not in the car. Forgot that.

I also found a 30 Ohm resistor in my stuff. While I am at it, I will connect that to the wire from the sender and ground it, so I can see if my guage will show about 10 PSI.

I'll be back...hope I can solve this soon...

[motornut]

the idiot one should be quite small in size,compared to the gauge one
in my case it was, when i swapped

[kikkegek]

okay, just finished some more research:

1. disconnected the oil pressure sender (no connection=max resistance) and the gauge shows MAX pressure

2. connected a 30 Ohm resistor in stead of the sender. The gauge moved a little away from zero, but didnt get to the first blank mark of the range. The specs from the sender PS152 are:
0-10 psi, 0-27 ohms,
60 psi, 65-90 ohms
so a 30 Ohm resistor should be about the same a an oil pressure of about 10-15 psi. so if the first blank mark on the gauge would be 15 psi, it should have been close to that. well...it wasnt...

3. I then connected the terminal from the gauge directly to the chassis. and then the gauge showed 0 psi. so MIN and MAX are correct. I am just guessing that the values in between arent very good anymore. Maybe the guage is off...




4. I then connected the oil sender again and turned on the ignition. and it showed 0 PSI. so it does make a good connection. When I then start the car. The needle shortly "shivers" and then just sits there around 0 PSI.....hopeless...

the only thing left to do is connect an Ohm meter and check the value from the sender with a running engine to see if it will give me higher Ohm readings when I rev it. but unfortunately it is about 0C at the moment over here (about 32F) and my hands were freezing. So I'll check that later afternoon.

I'll be back...

[kikkegek]

checked the oil sender unit and it measures 2 Ohm all the time. revving the engine has no influence. The shop thinks the sender might have been broken off the shelf and have ordered a new one for me.

[motornut]

wonder if you could use air compresser to check it?
hose and clamp over the end,of course lower pressures

[kikkegek]

thanks, but I know 99.9% for sure that it is broken.

I have connected a mechanical gauge and that shows 15 psi at idle and about 45 when I rev it...

I had my thought if the current "new" sender was making a good connection, but if it wouldnt, the oil gauge would have shown MAX pressure (no connection is like superhigh resistance).

since the current sender is giving me 2 Ohm at all times I know the connection is good, just not measuring anything...

[kikkegek]

finally new oik pressure sender came in the mail today.

Standard PS154T

At first I thought....owno, its just a switch, but then I found out Standard even has a T-series of a lot of their product...

changed it out 2nite and voila. oil pressure reading again.

so I have been searching for a problem, while my new sender was broken right out of the box

[motornut]

Originally Posted by kikkegek

finally new oik pressure sender came in the mail today.

Standard PS154T

At first I thought....owno, its just a switch, but then I found out Standard even has a T-series of a lot of their product...

changed it out 2nite and voila. oil pressure reading again.

so I have been searching for a problem, while my new sender was broken right out of the box

dam so it was eh

[kikkegek]

well...I am quite there yet.

tested some more today and the gauge goes up to about 10 psi after I start the engine, but then doesnt seem to response to engine revving...damn....so sick of it.

I ordered a 100 Ohm variable resistor now so I can check the gauge by hand...

[1Bad65GMC]

FYI,
Don't know if you know this but figure I would throw it out there since you have had all these crazy readings. If you do, ignore this.

You can't check ohms while the circuit is on and complete. You will get false readings. You will need to remove power and isolate componant.

The ohm meter supplies its own power. If you don't isolate the component you will be checking resistance of the entire circuit.

Just disconnect the connector at the sensor and test while running.
Posted via Mobile Device

[kikkegek]

Originally Posted by 1Bad65GMC

FYI,
Don't know if you know this but figure I would throw it out there since you have had all these crazy readings. If you do, ignore this.

You can't check ohms while the circuit is on and complete. You will get false readings. You will need to remove power and isolate componant.

The ohm meter supplies its own power. If you don't isolate the component you will be checking resistance of the entire circuit.

Just disconnect the connector at the sensor and test while running.
Posted via Mobile Device

check, thanks, did some testing 2nite

1. sender disconnected and connected a 100 ohm variable resistor in place.
result:
0 ohm = 0 psi
50 ohm = 15 psi
100 ohm = ~ 28 psi
it seems my gauge has a different range then the sender they prescribe for it. since the sender is 90-100 ohm at 60 psi.

the gauge does respond immediately to the resistor when I turn it up. so it seems fine.

2. connected mu multimeter to the sender and mass under the hood.
result:
engine off, contact off = 2 ohm
contact on = 20 ohm

engine on, idle 400 rpm = 85 ohm
1000 rpm = 90 ohm
2000 rpm = 95 ohm
3000 rpm = 95 ohm
so this sender also doesnt seem right or is meant as a idiot light sender.

I am lost here. am I measuring wrong? I dont think so.

I really want to keep the original gauges, but since my temperature is also off...I think I am gonna replace them with a simple two gauge panel like this...problem solved:

[hatzie]

GM volt, fuel, oil, and temp gauges use similar coil assemblies. They have application specific calibration resistors bolted to the rear of the gauge. This resistor is a white ceramic block with black resistance material painted on. The nuts that attach it to the gauge tend to dig through the resistance material over time causing the gauge to loose calibration.

1. Remove the plastic and steel shields and then one of the offending gauges.
2. Remove the resistor from the back of the gauge.
3. Look closely where the nuts contact the resistance material for areas where it's rubbed through. If this is the problem you will be able to see where the nut rubbed through the resistance paint. You may be able to re-use the resistor with some washers that are larger in diameter than the nuts. Make sure any ID paint present isn't keeping the washer from contacting the resistance material by buffing it slightly with 220grit emery paper.
4. If the washer trick doesn't work then you'll need new calibration resistors.

More in this thread... http://67-72chevytrucks.com/vboard/s...d.php?t=165596

[hatzie]

This is the one I was looking for.
http://www.europeancorvette.com/html/console_gauges.htm

[kikkegek]

wow, thanks, I'll look into that...

[kikkegek]

I gave up. I am so fed up with the gauges not working, that I decided to replace them.

I did some searching and found some really nice ones in England at McGills Motorsports:
http://www.mcgillmotorsports.co.uk/i...ewCat&catId=10

heres a couple of videos of them,

http://www.youtube.com/watch?v=xd65JLD7cME

http://www.youtube.com/watch?v=SP7bBr-7Nqw

When I get them I'll post some pics and videos here.

they come completely with sender and adapters..for only 20UK pounds each