High oil pressure (Guage) Searched!!!!

wvumtnbkr · 07-14-09, 10:36 AM

Good day!

well, my girlfriend and I just finished installing a drivetrain in her 87 GXL. THe motor is a (supposedly) rebuilt S4 NA. We are using everything stock, with the following exceptions: No emissions, no OMP.

The oil pressure guage goes fairly quickly to its highest value (pegged), but not immediately. I have checked the wiring to verify that it is not grounding out. (If it was, the guage would peg immediately).

If I take the wire off of the oil pressure sensor, the guage sits at zero.

Actually, that is incorrect, the guage sits below zero at maybe a 15 deg angle below zero. This is also where it sits when the car first starts (for a split second).

My car is inaccessible to determine if this is the "normal" resting position of the needle or not.

As far as I know, there have been no mods made to improve the oil pressure.

Basically, my question is:
Is it really possible to have oil pressure over 110 psi? Is it a faulty guage or sensor?

Would changing the front cover in some way lead to high oil pressure?

Thanks for the help!

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misterstyx69 · 07-14-09, 10:48 AM

sounds like a bad pressure sender( on the engine)
you mentioned changing the front cover.Did you put that Oil Pellet in the Eshaft?( I am not exactly sure of the Operation of the part,so I won't say anything else)

wvumtnbkr · 07-14-09, 10:53 AM

yep, I put it back in. Also, I followed the mazdatrix instructions so as not to damage teh torrington bearings.

I changed the oil pressure sensor that was originally on the engine before I ever fired it up, because it was dented. I am wondering if I should try to put it back on and see if it works. I am using a sensor off of a S4 JDM TII motor right now.

I will swap them around and see if I get a different result.

THanks for the input.

Rob XX 7 · 07-14-09, 11:22 AM

I see 80-90psi, but I have modifications to my system, your gauge or sender is not operating correctly.

You can change out the stock gauge and sender, or you can put a aftermarket one in.

rx7racerca · 07-14-09, 11:41 AM

Alternately, there could be a blockage in an oil passage - that happened to me years ago, thanks to an elastic band (used to hold the paper filter media together on some filters during assembly) on the crappy Fram filter I used. Thanks to the lousy construction in the Fram, the elastic bypassed the element, entered the block and blocked the oil feed to the head, which starved the cam and valves of lube and ruined the top end (it was a piston engine, obviously). In any case, immediately after changing the oil and filter, I noticed my oil pressure was unusually high - I initially assumed it was because it was cold and the oil was thick (it was -20C), but it continued to read high in normal driving over the next couple days - until squealing from the top end let me know my cam journals were done and I pulled the valve cover and found the starved head. Compressed air to the oil line blew the elastic back out via the oil filter outlet.
With the rebuild, I might not necessarily suspect the filter, but I would be concerned about oil blockages generally - if oil can't get somewhere it's supposed to go downstream of the pressure sender, you'll see high oil pressures. As has been suggested already, try a different sender, but if the story's the same, look for a blockage.

Rob XX 7 · 07-14-09, 11:57 AM

what leads me to believe its his gauge is that he says it sits below zero at rest, if you ground the sender wire where does the needle go?

HAILERS2 · 07-14-09, 01:43 PM

Pretty easy to figure out with little to no cost. Go to the ENGINE ELECTRICAL ..or it might be the Body electrical.

There you find out how to check out the gauges. For the oil pressure gauge you simply buy three/four resistors of the value shown in the picture. Then put the resistor on the output wire of the pressure sensor and the other end of that resistor to gnd.

The gauge will read a given value for each resistor shown in the picture. That should verify the guage being bad or the sender.

wvumtnbkr · 07-15-09, 08:35 AM

THanks! I will check this out as soon as I am back in my state.

P.S. I noticed the name of the screen shot you posted Hailers. Thanks for putting up with me/us.

vrracing · 08-03-09, 10:17 PM

We're having low oil pressure readings too and have been trying to diagnose it. We're showing 15 at idle and 45 at 3k rpm. The gauge responds really slowly too. The condenser is properly mounted and the oil sensor connector is clean. I jammed a male spade connector in there just to make sure the connection to the sensor was tight.

We swapped out another used sender (bent on top) and the needle pegged. I'm guessing the sender has shorted inside due to the damage.

So I went to Fry's to get the three resistors called out in Hailer's diagram. They really didnt have any exact matches. Looked at different combos to get the right ohms and realized in those blister backs it was going to get expensive. So instead I grabbed a 250 ohm single turn linear potentiometer for $6.50. It's a Canadian made NTE 501-0003 KU2511S28.

I soldered two leads to the pot and put a mail spade bit on one end which I would insert into the sensor wire and run the other to ground. I used the ohm meter to calibrate the pot and tested the gauge. Changed the setting and retested.

The gauge is good. Fricken slow, but good. Have a mechanical oil pressure tester on the way.

Anyway, thought I'd share the pot trick.

First gen man · 08-21-09, 11:38 PM

alright.. I've got a problem to tack into this thread.

I installed an aftermarket oil gauge on a stock s-5 jspec (with twin factory oil coolers) to find that I have about 30 PSI at 1000 rpm's and about 105 psi at 3000 rpms.

This doesnt seem right at all.. My stock gauge used to show about 80 max.

It is a cheap WM brand gauge, but brand new..

First gen man · 10-04-09, 02:55 PM

Anyone? I've noticed pressure drops when it's fully heated to about 90 PSI max. I am starting to get oil leaks from every oil connection in my engine bay including my main front seal.

Anyone have any answers on this? Could it have something to do with either of the two oil thermostats I have?

What about the dual oil cooler set-up? Everyone I seen talk about it says they lower pressure?