Hey guys,

Trying to get some information on diagnosis and what steps to take with my s5 13bt motor in my 1985 GS Rx-7. A couple of nights ago, I was driving home from work late and noticed very low, but steady oil pressure at any RPM, showing 25-30psi on my aftermarket and stock oil pressure gauges, and showing 10psi at idle.

Normally, I get 30-40psi at idle and 70-80psi under load at 2-3k RPMS. I stopped and checked my oil levels, and the oil level was full but smelled like fuel. From what I understand, it's normal for rotaries to get some blow-by, so I drove it easily home that night, and haven't driven it until I got a chance to check into it further today...

So, firstly I pulled the drain plug on my catch can and it was full of fuel! My last oil change was about a month ago, and I emptied the catch can then, with hardly any liquid being present in the catch can at that time. I checked the dipstick again, still full, dark brown in color, and still smelled like fuel.

Here's my fuel set-up:
-in-line Walboro 255lph pump
-stock s5 TII fuel filter, stock PD and rails.
(this was kind of a temporary solution that was running fine, but I knew eventually I'd have to get an aftermarket FPR to compensate for the aftermarket pump.)

At this point, I'm not 100% sure if the fuel in the oil is causing the oil pressure drop, but I'm sure that is causing some issues with it. I plan on buying an s4 fuel rail and fitting a banjo bolt, running an aftermarket FPR for the pump, and obviously changing my oil. I think that would be the right approach, before I decide to pull off the oil pan and front cover to check for internal issues, like the o-ring in the front cover to the oil cooler or a bad regulator.

I do have questions in regard to the s4 rails and FPR set up though:
What's the proper way to plumb an aftermarket fpr, is the Y-block I see used often in aftermarket fuel systems necessary for proper atomization? Or could one just run an in-line fuel pressure regulator into the fuel system without using the Y-block. (I am new to this sort of thing, and just trying to figure out how, and more importantly why)


Any feedback would be appreciated, since I want to make sure I approach this properly.

Thanks,
Ian

 

Oil thinned with fuel will give you low oil pressure....especially if it as bad as i sounds, maybe you have a leakin injector?

 

sounds like a MIA front cover o-ring.

verify oil pressure with a test gauge.

 

Update:

It's been a busy Christmas season with work, and today is the first day I had an opportunity to change the oil to verify whether the fuel in the oil was the only cause of the low oil pressure...It was not. I drained, and then flushed the system with an additional 3 qts of oil and let that drain, allowing any residual fuel to evaporate for 20 minutes before doing the oil change. Even while warming up, (mind you I did not go above 3000rpms) but I was only getting 30psi of oil pressure at 2-3krpms while driving and 15-20psi at idle.

Obviously the next step is to remove the front cover and oil pan; but beyond checking the front cover o-ring, oil pump, and pressure regulators, what other things should be checked in the oil system for failure?

Also, after parking the car at the house again, I checked the dipstick and got a faint smell of fuel, and had residual fuel in my catch can. Would a front cover o-ring allow this much fuel back into the system? or do you think I am having compounding issues.

Thanks again for the feedback,
Ian

 

Compounding issues is my vote. My engine is ragged out(s5 na) and the oil smells rancid of fuel after 500 miles but still gets proper oil pressure when fully warmed up(~24psi with oil temp at 185*)

 

Have a similar issue with my 10th...

A few things to verify (or re-check, even if you already looked into them):

- engine compression levels (you could have excessive blow-by due to a failing side or corner seal, or more...)

- fuel pressure before and after the regulator to check for bad regulator and/or pump

- fuel pulsation damper

- as already mentioned, leaking or stuck injector(s)- this could also be an electrical issue, not just a failing injector

- timing

- EGR and crankcase ventilation system operation

- O2 sensor functionality and continuity of wire to ECU

And, obviously, as many have said- double check the oil pressure levels and diagnose for internal system failures/leaks.

Neal.

 

UPDATE:

Borrowing a friends garage to do the work and we started with a compression test today:
We used a craftsman piston engine compression tester, and overall I was getting good readings. All of the readings were done with a new battery and the throttle at WOT.
- 50-55psi consistently on the front rotor (holding the bleed valve open) and 100-105 psi when letting the pressure build on three rotor faces.
- 50-60psi consistently on the rear rotor (holding the bleed valve open) and 100 psi when letting the pressure build.


The fuel in the oil is what's really worrying me, I did NOT drive the car more than 4 miles from when I last did my oil change in December and had a large amount of gasoline in the oil pan again when I drained it this evening. I pulled the vacuum line for the regulator and pulsation dampener, and did not have any leaking gasoline, however I am still seeing/smelling gasoline residue in the oil catch-can and oil pan.


I have purchased an Aeromotive aftermarket FPR and a parallel system that will be installed as I'm pulling the front cover and refreshing the oil system (new front cover o-ring, new oil filter pedestal o-rings, and checking the regulator and eccentric needle valve for proper tolerances.) When this is done, I will be checking for leaking injectors to rule that out as a culprit. but I'm hoping the aftermarket FPR will fix the fuel issue, and refreshing the oil system will fix the low oil pressure.

Should the oil pump be pulled off the motor and checked for tolerances as well? Or are there any clear indications of failure without removal.

Thanks again for the input,
Ian