Let's Talk Low Oil Pressure in a TBI...

So as some of you know, my wagon didn't make it to VA due to a weird low oil pressure issue. I'm starting to run out of ideas and don't know where else to go. This started post intake manifold gasket replacement. It should also be noted that post intake I didn't quite get all the air out so it got hot, but not into the red "danger zone" at any point. It was also only hot for about a minute, shut the car off, cooled it off, reburped the system, Retimed and off I went no more temp issues. Driving home the next night (car sat 24 hours to let everything dry/set) once the car reached temp (180F) oil pressure would drop, ultimately leading to a stall. Checked the usual suspects, grounds, etc no issues put a mech gauge on it, it still moves down at temperature. There is ZERO noise that would be out of the ordinary, no metal on the drain plug. So began the replacing of parts. As of now I've done the following.

-Fresh oil/filter. Mobil Super 5-30 and a Delco filter
-New block pressure sender
-New dizzy with ICM
-known good, but used ESC

None have gotten me running reliably again. I would also like to think the minute or so it got hot would not cause a head gasket issue since I have good temperature currently. It should also be noted that over the summer the motor was removed and the top end refreshed with a new cam and injectors. Motor has appx 2500 miles on it since the rebuild with no prior issues except the aforementioned intake job.

The stall would lead me to investigate a vacuum leak,.resulting in slow idle resulting in the low oil pressure,.?

does it stall all the time? or just warm?

is it a roller cam engine or flat tappet?

phantom 309 wrote:

The stall would lead me to investigate a vacuum leak,.resulting in slow idle resulting in the low oil pressure,.?

does it stall all the time? or just warm?

is it a roller cam engine or flat tappet?

Just when warm and in drive, pressure holds fine at temp in park. Stock roller LO5

turn the idle up a little,.

phantom 309 wrote:

turn the idle up a little,.

Via the dizzy? I didn't think there was an idle screw on these.

It could be that the pressure relief valve in the oil pump is sticking open when it gets hot. The spring could be weak when hot as well. Changing the oil pump is going to take most of the day. Remember to remove the distributor cap, and the trans dipstick before lifting the engine. I also replaced the nylon coupler for the distributor drive with a metal one, so I never have to worry about it again. The crank must be in the 6:00 position to get the pan out. You also have to remove the oil level sensor before dropping the pan, or you will break it off.

I had a pressure relief valve stick closed, and it squeezed the oil filter gasket out, then sprayed a wedge shaped stream of oil about 20 feet out of the side of the car.

Cadet57 wrote:

phantom 309 wrote:

turn the idle up a little,.

Via the dizzy? I didn't think there was an idle screw on these.

i just read you changed the cam,.. ?

you recalibrate the chip?

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What cam?

Did you change the oil pump when you had the engine out?

jayoldschool wrote:

What cam?

Did you change the oil pump when you had the engine out?

L98 cam. Did not replace the oil pump, cleaned out the screen and inspected. Reinstalled.

phantom 309 wrote:

Cadet57 wrote:

phantom 309 wrote:

turn the idle up a little,.

Via the dizzy? I didn't think there was an idle screw on these.

i just read you changed the cam,.. ?

you recalibrate the chip?

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Yes I did. Chip was tuned professionally for the new cam, injectors, and AIR delete.

Going to order a new oil pump and hope for the best. I *really* don't want to do another motor

fwiw my oil pressure gauge on my car reads 0 at idle when warm. i run a thicker oil-10w40 or something like that.

why would it be stalling though? the tbis use the oil pressure sensor as redundancy to trigger the fp if the fp relay goes. i think... fred knows for sure.

maybe if your fp relay is shot and its relying on the oil pressure sensor and it senses 0 when warm it cuts out the fp?

Thought about the fuel pump relay, especially since it's in the tangled weave of oil pressure switch, ICM, and ESC. However, until this issue my gauge has always reads around 30 at idle and 60 under load. So I think the only role the FP relay plays here is that it's correctly shutting the car off when the gauge drops to under 10 psi.

Turn the idle up a little,.

phantom 309 wrote:

Turn the idle up a little,.

Going to try that on a spare TB base I have. This is a new experiment for me so I don't want to mess up my "good" stocker. Thanks for that link BTW.

Did you replace the cam bearings when you installed the cam?If so,were you careful about the oiling hole alignment?

Flasheroo wrote:

Did you replace the cam bearings when you installed the cam?If so,were you careful about the  oiling hole alignment?

I didn't do bearings under the thought of "not broken, don't replace" The old cam didn't have any excessive wear so we decided to leave the bearings alone.

TURN UP THE DAMN IDLE!

Welp, its not the idle. Turned it up a little, pressure still comes down. Guess next step is an oil pump.

I did an oil pump, and it was not all that bad. The major work was installing the pickup on the pump body. Get a metal connector for the pump drive from the distributor. The nylon ones tend to crack and break. I hope it cures the pressure problem.

Yeah, RA has the metal coupler so I ordered one of those as well. Just wondering what size I'll need though. There are two sizes, 5/8 and 3/4 for the pump sizes. Wonder if its a car to car thing.

Cadet57 wrote:

Welp, its not the idle. Turned it up a little, pressure still comes down. Guess next step is an oil pump.

whats the idle rpm now in gear>?

phantom 309 wrote:

Cadet57 wrote:

Welp, its not the idle. Turned it up a little, pressure still comes down. Guess next step is an oil pump.

whats the idle rpm now in gear>?

Bumped it from about 970 (according to the timing light) to about 1100.

I believe the correct one is the 5/8 inch. I think the 3/4 inch one is for the big blocks.

1100 rpm in gear?

wow,.

phantom 309 wrote:

1100 rpm in gear?

wow,.

Like I said, around there. I moved it back to 970 when I noticed it didn't make a difference.