I have a '90 GXL, all stock w/ ~37k on rebuild, 175k total. The other day I changed my oil, but couldn't get the filter off (I was in a hurry to get to work) and ran the car to and from work on the old filter, which was changed 3k miles before. Driving home from work, stuck at a long red light, I notice my oil pressure gauge is reading near 0. I blipped the throttle a bit, and the pressure rose a bit... not a dead gauge. Got to a friends house, he said it was most likely due to not changing the filter. Changed the filter last night, along with the fuel filter. Started my car up, and it smells like a lawnmower engine. No smoke comming out the pipes, but it smells heavily of oil. After a few minutes of idling (letting the car get warmed up) the smell starts to fade out a bit but I notice the oil pressure gauge is nearing 0 again.

 

Tap on the oil pressure sending unit below & forward of the filter (can't miss it- one wire going to it)...Does your gauge move?

 

Thanks for the quick reply, Wayne.

RED - This was unplugged when I went outside to try this "tap test". Plugged it back in, didn't change anything. What is it?

GREEN - This is what I tapped on, which had no effect on the gauge. This is assuming I tapped on the correct thing. :P

BLUE - Found this connection behind the oil filter. Seems to run up behind the intake manifold area, can't really follow it past there.

YELLOW - This is where the plug was found, before I moved it to be photographed.

 

Flipped through the Haynes manual, couldn't find anything on oil pressure (index says page 74, but that is prepping the engine for removal.. I hope I don't need this page )

Wayne, for your "tap test" I simply tapped the unit circled in green (double checked, its the correct unit) with a small screwdriver with the car off, set to ON, and running... gauge didn't bounce at all during the "tap test" and the gauge still does what its been doing.


Start the car, it idles at ~30psi st first, slowly drops down to near 0. Blipping the throttle makes it rise a bit. Under load/decent acceleration, pressure nears 60psi but doesn't go over it. Pressure stabilizes to arround 45psi after letting off, slowly drops to 30 to hang a bit, then continues its downward spiral.

 

oil pump??? I had a 200sx that would do the same thing turned out to be oil pump.

 

The blue plug is your relief solenoid valve (S4 cars, anyway), it controls the "overboard" air for your ACV...

Blue circle, not sure, maybe an S5 thing. It's in the general area of the purge control valve on S4's, or perhaps the air bypass solenoid valve...

I wonder if you blew a front cover o-ring...

 

Well, there is oil under the car, especially near where the tranny meets the engine... but the car doesn't leave spots on the driveway, and I'm not losing any oil.

Edit: Found THIS: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/low-oil-pressure-idle-searched-303379/ : thread, will try the pellet thing tomorrow.

 

That area might be your rear seal, but I don't think that would affect your pressures the way you're describing, unless it's totally crapped out (then you'd have a nice big oil spill back there)...

 

I'm fairly certain the oil I see under the car is from the previous owner... he must have had a MASSIVE oil leak because there is oil all along the bottom of the car.... like it even goes onto the diff.

Also, when I posted the pic... I said the wire goes to the intake manfold... I wasn't thinking clearly. Its behind the throttle body.

 

Update: Still trying to get the pellet out... after spending all day trying to get 2 rounded-off nuts off the mechanical fan, we finally just hacksawed them off and will just use the other 2 bolts to hold the fan on until i get an electric fan. Now, we can't get the e-shaft bolt off that has the pellet inside via spring... whenever we try to move it with the breaker bar, all the pulleys on the car move (yes, its in gear).

 

Yeah, that thing is a PITA with the engine in the car. Some guys have to just put a breaker bar on the bolt, and rest the end of it on the left frame rail, then hit the starter for a split second to break it loose.

You should also be aware of the consequences of breaking that front bolt. There have been instances of one of the needle bearings (thrust bearing) falling behind the spacer after the tension of the front bolt is taken away from it. Mazdatrix has an excellent writeup on this, check out their website, in the FAQ, I believe...

 

Does any one know much a oil pressure gauge cost? would it save more time if he just buy one and check the oil pressure from the block?

 

Wayne - Thanks for the mazdatrix info, checked out the FAQ and will definately remember that. As for the breaker bar +starter idea, I tried that already. I really can't think of another way to get this thing off... I guess for the time being I'll just have to rev a bit at stop lights.

 

hey gimme an update on this, I have a similar problem. I'm hoping it's just a clogged oil filter, will be changing the oil tomorow. I read that pellet faq and it seems all that the thing does if it fails is not raise the oil pressure from startup conditions, which would not leave you at 0 psi.

 

No update for this particular problem yet... I believe my 5/6 ports are stuck closed, so I'm just going to take the car to Marvelspeed and let them poke around at it a bit.

 

My oil pressure sending unit is pretty dead. It usually reads lower than 30 psi, occasionally it crawls up to 45 psi, but most of the time it hovers around 0 psi. However, my VDO gauge reads 30 psi at idle and 60-70 psi depending on RPM and load.

It could just be that the sending unit is dead and won't even really respond to tapping. You could also try cleaning the connection where the wire slips on the sending unit.

If you can get ahold of a mechanical oil gauge, just put it in place of the sending unit and rev the engine to see if the oil pressure is truly what the gauge says it is.

 

I drove a '90 GTU 560 miles with the gauge on 0 the whole way and it ran fine. I think its just ancient technology.