Rattaan

Just a few days ago my oil pressure guage started reading at about 60 (in an S5) at start-up and began to slowly drop to 0 in around 2 minutes time. I replaced the guage almost 2? years ago because my old one got burned up when the sender went bad. So the sender was also replaced at that time (I'm thinking it was made in Mexico?).
I didn't drive the car that day, and when I came home I decided to check the electrical connections after reading about so many problems on oil pressure here. I removed the clip to the sender and cleaned both contacts well. I put it back on and started the car. The pressure went to about 30 upon start-up and dropped slightly after becoming warm. If I revved the engine for at least 30 seconds it got to 30 again but no further. I then tried pulling the sender clip off to see what would happen and clean it again. After pulling the clip while the car was running, the pressure gauge veeerrrry slowly dropped to 0.
Here's the problem I want to address though. ever since the first time the sender took a dump, the gauge moves exceedingly slow. Thanks to Icemark , I know that there are other parts to the system other than just the sender and gauge. I just don't yet know how they work together.
What I'm wondering is, has my sender gone bad, was it not as sensative as my original sender, did the gauge I replaced just suck from the get-go, or is there something wrong with the condenser? Or any combination of these? Also forgot to mention the condensor is well grounded to the clutch slave cylinder, which has an extra ground running straight to the chassis.
I haven't yet purchased an attachment to my compression tester to check the actual oil pressure but I'm sure it's probably fine anyway. Should I get one to be sure, or look to replace the sender and condensor? or just the condensor? or what?

HAILERS

Two ways:


1. Go to the Pepboys and buy a somewhat cheap SunPro mechanical oil pressure gauge. They'll have several adaptes with it. One will fit your oil pressure senders threads. Pull your original sender and install the SunPro sender and gauge. You don't have to run it inside the car. Just the engine compartment. Start the engine and see what the REAL oil pressure is.

2. If the pressure is decent i.e. approx 30psi at idle and 60 plus at 3000rpms, then you have a problem with your original sender/gauge unit.

3. If that is true.....then open your FSM. Go to the METERS section. There it will imply that if you remove the senders wire, and connect a 2k ohm resistor to that wires end and the other end of the resistor to ground, the gauge will read approx 30psi if the key is turned to ON and you wait a couple of minutes. Also 1100 ohms equals 60psi and 800 ohms equals approx 110 psi. Those figures are out of a 91 fsm manual.

4. IF the mechanical Sunpro shows some dreary figure......write back on this thread and we'll tell you how much trouble your really in. (humor)

Rattaan

Thanks man. I haven't gotten to the METERS section of the manual yet(which part is it in??). I'll go ahead and get the tester gauge and try it out. I'm warning you though, if you jinxed me with your humor bit I'll be hunting you down

HAILERS

Section T of the 91 manual. Called Instrument Cluster

Kai

Body electrical, section 15-25.

EDIT: oops, sorry, that's the S4 manual. Just ignore me.

Rattaan

Ok here's the deal. I went to radio shack and bought some 1k resistors. I wired up a pair in series and attached one end to the harness for the sender and the other to ground. Result, nada. No movement whatsoever of the gauge. Removed one resistor. Also nada. When I grounded the harness(0 resistance), it pegged the needle.
I then pulled the sender. Plugged in a mechanical Sunpro oil pressure gauge. Started the car. Slightly over 60psi. Let the car warm up, and it went to slightly over 20psi. Revved a few times, needle moved quickly to around 60 and dropped with rpms. So obviously no huge worries.
I then checked the resistance of the sender itself while removed from the car and got 800 ohms. Put it back in the car and started the car. It read 200 ohms to ground. plugged it into gauge. Gauge reads 2/3 up under 30 psi. Revved engine, no change in reading.
By my deductive reasoning, I figure the sender is crap. I also wonder if there are different resistance ratings for my '90 as opposed to the '91's? Anyone with any other opinions here? Any info is welcome.

NZConvertible

You might as well just leave the mechanical gauge in place. It'll be better than a functional stock gauge anyway.

Rattaan

I would, but it really doesn't match my interior at this point in time. Nor do I really have anywhere to put it. When I eventually rip the car apart and make it into a race car(years away probably), I'll put in new guages that are only necessary to make sure the car is running properly. But for now, things are staying stock.

HAILERS

I'm looking at a 88fsm online and it says at 30psi for a 88 model you would use a 196.7 ohm resistor, for 60psi you would use a 141.2 ohm resistor and for 110psi you would use a 102.6 ohm resistor.

Sorry, I don't have the 91fsm near me right now. So I wonder if somehow I wrote the wrong figures down.

Rattaan

I wondered about that. I looked at the FSM on FC3S.org and it said to plug in some checker, so I wasn't sure where the resistance values you gave me came from I was looking for the part number for the oil pressure sender. I plan on getting a Mazda sender this time, and see how things go from there.

HAILERS

Nope. I just looked at the series five online and what happen was an eyesight problem. Blurred vision made me see the ohms symbol as a zero. OOOOPS. So its a little different. 30psi is 200ohms, 60psi is 110ohms and 110psi is 80ohms.

Their checker is just a set of resistors of the values stated above. You should be able to accomplish the same thing using store bought resistors.

Tell you what. Check for yourself the figures in the manuals that are online since I've give so manyu different figures. But they will be quite different than the original figures. Don't trust anyone.

http://www.fc3s.org/how_tos/manuals/89_fsm.html

EDIT: Page T39 of the 89manual.
EDIT: OH! I SEE! The figures come from the picture of the gauge face. Look in the manual again and look for the picture of the gauge face. It shows the resistance values there. If you don't find the picture......let me know and I'll give you the page number. No time right now.

http://www.fc3s.org/how_tos/manuals/88_fsm.html

HAILERS

This:[IMG]: watermeterface.jpg[/IMG]

HAILERS

This:

HAILERS

BIGGER

Rattaan

Ok, now just out of curiousity what does the condensor do? Or better, why is it there? Does it slow the needle movement or something? What exactly does it connect to when it goes into the wiring harness? And one last one, does it ever go bad?