Greetings all. Not new to the forums, but I am new to older-gen Subarus.

I just picked up a 1985 Brat a few weeks ago. Now I seem to be having issues with the oil pressure.

Details, in case they are relevant:

1985 hydro lifter EA81. 133,000 miles, everything seems in good mechanical shape. Fresh 10w-40 oil and wix filter. Resealed oil pump and new sending unit. Idle set a little high at 800/850 (gets shaky with the AC on otherwise). Weber carb, and 5 speed DR swap.

 

So a little backstory. The Brat was running great and showing no problems until a friend and I decided to take a ~2hour trip. The oil pressure had always jumped up to around 50 when the Brat was first started, and settled down to around 25 both while driving and idling (this is on the dash gauge, which I know tend to be unreliable at best). Near the end of our trip, we noticed that when stopped and at idle, the oil pressure gauge would drop to 0. Ok, fine, I got an oil pump reseal kit with the spare parts that came with the Brat, and I figured resealing and inspecting the pump would give me peace of mind anyway.

So I drained the oil and pulled the pump. I measured it as best as I could with feeler gauges, and everything looked to be in tolerance. Physically the pump looked to be in great shape, no signs of wear that I could see. The O-rings were flat and a bit crispy, and the small O-ring on the outside was folded over a bit. I thought for sure that would be my problem. While I had the oil pump off, I did the method suggested in the keep your Subaru Alive book, and used a piece of hose to blow back through the oil inlet. I could definitely blow some air through the hose, but there was resistance (could be normal?).

I got the resealed pump back on, fresh oil and filter, and same thing; when first started, oil pressure goes up to around 50, and settles to 25 at idle. Go on a short drive, and the oil pressure drops to nothing when stopped at idle. I should probably mention that I don't hear anything amiss (lifter noise etc.) when stopped. So after this, I noticed the oil sending unit was leaking oil...so why not, I went ahead and replaced it too this morning.

Again, same behavior, pressure drops to 0 at idle after a short drive.

So anyway, my actual question. Is there a good place to connect a shop gauge other than where the oil sending unit mounts? If possible, I would like to leave the sending unit connected so I can compare the dash and shop gauges. I realize that I probably should've started with the shop gauge anyway, since the dash gauges are a known-issue...but I do want to get a real gauge on there before I pull the oil pan and start checking the oil intake (looks doable, but a PITA with the engine installed?).

 

...and pictures, because why not?

Nice ride mate, jump seats and all!

On the rhs of the oil pump opposite the filter mount is/should be a hex key plug. This is where the oil light pressure switch is mounted on the "povo" pack vehicles (like mine).

This should be a good spot to tap an aftermarket oil pressure gauge into. Removing the hex key is the trick

Cheers

Bennie

Make sure you get a British tapered pipe thread adapter.  That port is not metric, or NPT.

DaveT -  I am also want to install an aftermarket oil gauge...  Have you installed one using this port?  If so, where would one buy the British pipe thread adapter?  Size?

Thank you for the heads up.

Yes, that port is where you can install an after market gauge.  Some of the gauge companies also offer adapters.  I also know that Amsoil had a kit with them for the bypass filter.

Thanks for the suggestions, I do remember seeing that port when I had the oil pump off. I have an industrial supply store close to me that should have any thread that I need.

I hope to find with a shop gauge that my oil pressure has been fine all along, and that the dash gauge is junk. I would like to get back to driving this thing!

Edited July 31, 20187 yr by Evinrude

There is a second port on the side of the EA81 oil pumps that is used for the pressure switch on DL and STD models, or digital dash cars that are not equipped with the pressure gauge option. This port is usually fitted with the square head pipe plug that is 1/8" BSPT thread. Remove this and install an adapter such as this one:

https://www.amazon.com/GlowShift-Female-Sensor-Adapter-Reducer/dp/B00NWZ3TUI

And from there you should be good with any mechanical shop gauge as most will handle 1/8 NPT out of the box. 

That said, you probably need a new sending unit, and it is technically acceptable for the gauge to read 0 at hot idle. Says so in the owners manual even. The sending units are crap especially when old. Generally speaking you want at least 10-15 psi at a hot idle. The general rule is 10 psi per 1000 RPM of engine speed. Subaru engines are usually higher than this though. 

GD

 

McMaster-Carr part number:

4936K408

https://www.mcmaster.com/#bspt-to-npt-pipe-fitting-adapters/=1dyf6ni

Edited July 31, 20187 yr by czny

19 minutes ago, GeneralDisorder said:

That said, you probably need a new sending unit, and it is technically acceptable for the gauge to read 0 at hot idle.

Good info, appreciated. I recall seeing the square shaped plug too. I didn't realize 0 at idle was OK (I have a "Keep your Subaru Alive and a Haynes manual, still need to find an FSM). I seem to remember my friend's EA82 keeping 50+ on oil pressure at all times, so I was thinking mine was reading low. Sounds like I'm still in good range with the per 1K rpm rules.

I installed a new sending unit this morning with no difference. I hope to get the shop gauge connected in the next few days, I'll report my findings.

In the past on various vehicles I've used a T fitting screwed into where the oil-light switch is and screwed the oil-light switch into one end of the T and the guage line into the other end of the T

Having said that, I have not done it  on a Subaru so possibly access/clearance might be an issue on them.

On the Subaru oil pump, if you have the oem gauge, the port for the pressure switch is plugged, so you can just use an adapter and connect the mechanical gauge there.

Wow, same message about five times over now :p

hooefully he's got it sorted

Cheers

Bennie

He is probably out and about in his little ute :)

I have read in here someone saying not to run both idiot light and gauge senders together. have one or the other but not both.

I read this after I did this to my utes EA82, well , actually was an EA81 at first.

With 15W40 I can see 100 psi on my gauge when cold and maybe revving more than should. When everything is warm and at idle speed of 800 rpm I keep seeing the needle drop to zero, but there is no knock, no other indication of problems and pressure picks up as soon as I give things a squirt again. Every pump I have done has been in spec - yet not pulled all the pressure plugs and springs - they don't want to come out !

Update, got my shop gauge connected today. I used the port with the square nut, and my gauge  threaded right in, no adapter needed. 

 

Surprise, surprise (no one is surprised) the dash gauge is way off. At cold idle I’m reading around 55, and up to 70 with a throttle blip. After everything warms up and the dash gauge goes to 0, I’m still showing around 20. Again, with a blip of the throttle it jumps back up to 50. 

So now I feel a lot better, and my paranoia is satiated for the moment. I plan to mount a nice/working gauge on the inside eventually, but for now all is well. 

 

Edited August 2, 20187 yr by Evinrude

Nice gauge.   What brand and is it a kit?  Where you get one?

1 hour ago, rdweninger said:

Nice gauge.   What brand and is it a kit?  Where you get one?

https://m.harborfreight.com/engine-oil-pressure-test-kit-62621.html?utm_referrer=direct%2Fnot provided

 

It’s the kit from Harbor Freight. Like most tools from there, it actually works pretty well for a DIYer that only uses it occasionally.

not much to break on a gauge.  I like the 5'  6"  hose.    Thank you for the info.

Just run that gauge into your dash - it is an aftermarket one in my ute that reads zero,  not a factory gauge !