The problem - TL/DR:
Hello club, it's been too long! I haven't posted anything in probably 14 years, and now I need some help. As the title states I am having issues with oil pressure. Running Valvoline VR-1 20w-50 At first start up I have between 50-70PSI. When oil reaches about 170F I have between 0-3PSI at idle (900rpm) and revving to 3K produces something around 15PSI. It reads roughly the same on both the dash and the AEM 0-150PSI Oil pressure sending unit in the sandwich plate on the oil tower.

Back story:
I rebuilt and ported it myself over 10 years ago. I did not replace the rotor bearings due to lack of equipment at the time. So they were used, and I do not know if they were in spec. I replaced all seals and springs with new, but didn't fire it until last year. I was learning how to road tune the ECU myself, so I did this N/A. A slight learning curve, but otherwise it runs great, no complaints there. I put about 1000 miles on it N/A, getting somewhat aggressive with it at around the 900 mile mark. A few donuts, and a burn out. Letting her sing in the upper RPM's to my 7500RPM redline setup in the ECU a few dozen times. All seems groovy.

I pulled the motor to paint the engine bay, and add some upgrades to the sensors situation and go through the wiring harness. Dash oil gauge didn't work at the time, but due to an unfortunate oil to turbo line mistake in the driveway the year prior, I was quite certain I at least had ok pressure. It was a lot of oil, in a very short time. Don't worry that was while still running the eBay turbo (not plumbed to the intake) since I waited a year to get my BW 7670.
After the bay was pretty, I reinstalled the motor with my new turbo and figured its finally time to plumb the turbo to the intake, but I want all the data. I didn't have much fear of hurting an N/A turbo block while learning to tune, but I know boost is a different game. So, I added Oil pressure, Oil temperature, fuel temp, fuel pressure, and Flex sensors. I also fixed the broken wire leading to the dash oil pressure gauge.

So far I have checked the O-ring to the front cover. The first time I checked the O ring it was good, and I put it back together. Same issue. Second time I checked and swapped out the oil pump, yes the locking screw is in the pump, and I checked the front cover pressure relief valve spring. All good there.

Any ideas:
I feel like this has to be either a bearing clearance issue since I never changed them, or I have even read about possible cracked stationary gears. Maybe my pickup is sucking air? Last thing I have yet to do is one final test with my mechanical pressure gauge just to verify both oil pressure gauges that read the same on a cold startup and all the way through warm up when pressure drops to essentially nothing are wrong to confirm the lack of oil pressure. I have not double checked the OPR or the pick up tube since I didn't remove the oil pan when I checked the O ring and changed the oil pump, just the front cover. The OPR (85 or 90PSI I believe) was brand new from either RB or Pineapple, I can't for the life of me remember. Too many years ago.

Seems like such a shame considering it runs so well, and the literal hundreds of hours I have into this doing every single modification listed above and below by myself. Any rotary guru's with an idea of what this could be? It would be such a shame to have to tear this down again. I was really looking forward to tune the boosted side of this thing. Like I said even N/A although very underpowered, she rips! I just feel like if I had low oil pressure before I got the gauge working, and the new AEM one that there should have been some sign that something was wrong. Smoke, weird noises.. something. Maybe both gauges are wrong. I'll update this when I get my results from that last test.

Anyone have any ideas? If I could possibly have missed necessary information, please let me know.

Thanks.
SONIC7

About the car:
*1987 Turbo II large streetport (I did it) very little if any smoke, probably from heavy premix for the break-in
*S4 rotors, front cover, E-shaft - with stock oil inserts, and Irons
*S5 Rotor housings
*Atkins thermal pellet
*Pump gas for now, E85 in the future
*Valvoline VR1 20w50
*AEM 0-300F OIL Temperature sender at the filter pedestal, and secondary sensor in the old cold start switch hole in the oil pan
*AEM 0-150PSI OIL pressure sender at the filter pedestal on RB sandwich plate
*Either RB or Pinneapple 85PSI or 90PSI oil pressure regulator I honestly don't remember, but it is not the stock one
*stock pick up tube
*Atkins oil pan baffle plate with 2x gaskets
*Same with old and a new oil cooler
*front cover O ring and plastic keeper checked twice, good
*Oil pump seemed ok, was replaced. Same issue

non relevant info
*ALS apex seals
*Atkins rebuild seal kit
*Adaptronic Emod009 PnP
*AEM 0-100PSI fuel pressure sender
*Continental Fuel Flex/Temp sender
*Walboro 400 pump
*ID1050 primary and *ID1700 secondary's
*FFE Fuel rails
*no OMP, running pre mix ports are blocked off with a block off kit.
*RB SS oil cooler lines
*RB Rev II silencer back exhaust
*BorgWarner 7670
*3" downpipe off turbo
*6 puck sprung street/strip clutch
*DC Power 180A Alt
*Atkins grooved pulley and belt upgrade
*Koyo Rad
*CX Racing Bar and plate FMIC
*No emissions controls on the vehicle
*running VE, no MAF
*stock coils, stock CAS

 

Sorry to know about your problem. This is way over my head. I just happened to stumble across this low pressure guide in the FSM for a S4 looking for details on the OMP. Yours is intermittent so this may not be useful. I will give you a bump anyway....

 

Thanks, Jeff. I appreciate the feedback and support. That is what this community is all about. I'm going to do a write up of my findings here shortly.

 

Well I had a chance to do some testing with the mechanical gauge this evening. I don't know why I didn't do this before. I picked up a threaded adapter to go from the stock oil pressure sending unit location into a normal 1/8NPT sensor female. To my absolute shock and delight, both my dash gauge and AEM 0-150PSIG are not reading even close to what the mechanical gauge reads. I think/hope.

Does anyone know about issues with taking measurements from the filter sandwich plate? Is AEM, the brass ones at least, just not producing good or accurate products? What is going on here?

First, I did a cold start and took some screen shots of the video that I filmed. ECU is seeing 62PSI


As usual, the startup pressure is absolutely great. Sitting at 62PSI at approximately 1800RPM to the ECU. I haven't fully tuned the startup enrichment or BACV values yet. Still working on that part.


The dash gauge is happily showing, well.. that oil pressure is existing and is claiming =/-50PSI

I through the mechanical gauge on to the 1/8NPT adapter to screw into the stock sending unit hole. 68psi. Even higher than the ECU is seeing. This is all while the engine is still cold and doing its warm up thing at about 1800rpm.





Ok, so now the engine is fully warmed up and is doing the thing I started this whole post about. 950RPM, 185F and reading 4PSI of oil pressure. I've seen 0 before.


However! The mechanical gauge is happily registering 41PSI at 950rpm. Well i'll be. How is this possible? It has to be a failed sensor... right? My AEM 0-100PSIG sensor on my fuel rail is in lock step with the mechanical gauge on the FPR. So, perhaps it is just a bad unit?



Revving it I couldn't see the laptop at the time for the RPM, but It shot straight to 75PSI on the mechanical gauge. The ECU is only showing mid teens at this point.



I decided to relocate the sensor to the stock oil sender hole. While it didn't return the results I was hoping for, there was absolutely improvement to the numbers. When i start tuning I'll have to keep my eye on the range it goes to.. or maybe I try another brand of sensor. What do you guys think, any recommendations for sensor brands? Is AEM (the brass versions at least) no that good? I've heard people recommend the stainless steel version. Maybe this is why.




Mid 20's in the stock hole at idle






High-ish 30's when revving on the AEM now. I feel confident that I do in fact have oil pressure, to say the least. I am open to suggestions for brands of sensor I pick up to try. Is there anyone else running a RB sandwich plate for sensors under the filter? Thanks guys.

SONIC7

 

Try measuring the resistance of the sending unit wire. It may be broken, or near breaking. If it's high resistance, replace it