Info request related to low oil pressure

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Dec 1, 2017
Ahhhh hello all, I’m a 1988 FJ62, engine rebuilt a year ago, my 2 quick questions first:
1. Does anyone have a link to the FSM that includes the lubricant system?
2.Does anyone know the torque setting for the bolts on the connection rod near the top left of this image below.

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So long story short... I’m being plagued with low oil pressure. Truck starts fine. No smoke/blue smoke. Sounds and performs well. When the truck starts the oil pressure gauge waits, then pops to the bottom of the acceptable range. Over the next 10minutes(give or take and depending on how much red light idling I do) the oil pressure slowly drops to basically below the very last indicator line on the gauge. I would be below the red if it was a fuel gauge for reference.

It then more or less stays there until the truck turns off and the gauge drops entirely.

I have:
-checked with a full screw in mechanic oil pressure gauge (same result)
-oil changes with much heavier oil.
-replaced pressure sending unit
-replaced the oil pump.

Many thanks.
The pressure seems to stay pretty consistent under load. But anytime she slows down or idles then the slow drop continues. I don’t gain pressure under load so much as stop loosing it or loose it too slow to notice.
And thanks for the reply!
I have not gotten a compression test done as of yet,
These 2f engines are pretty durable.

A compression test will confirm if there is an issue.
Check the PCV @ the passenger side firewall, it can get congested, is there any oil getting into the air filter?

I see you said no blue smoke, which is a good sign.
Sorry just have to ask... PVC?
There was no oil in the air filter last I checked though. I will take a look tonight again to confirm. No extra oil anywhere that I can see and the oil level stays very consistent as well. (Is there any type of pressure release gauge by chance?)
Appreciate your time, :)
Gauge was plugged into the engine block, by the oil filter and where the original pressure sending unit is located.
Ok. So where you tested is appropriate, but if you don't know the measurement units, you may want to re-test - as it could be fine.

The fact that it runs well, with no bad noises - and changes in viscosity don't impact the pressure readings makes me think you either have a bad gauge or a possibly some kind of restriction in the galley where the gauge is reading.

Have pressure readings been low since the rebuild? Or is it a recent issue?
In that image, the torque values for the con rod cap are right below the words 'Connecting Rod Cap'. I believe the '43' is lb-ft, for us English types.
Pressure was maxed post rebuild(in retrospect possibly too high as it read above the gauge). Then on day I looked down and was loosing oil pressure, about I months post rebuild.
It was a defined switch though. It was very high and has never been like that/consistent since. It’s been like this for likely 6months now but she isn’t a true daily driver. Lucky enough to walk to work.

I will track down a mechanical gauge again for retests and look into the PVC.
Many thanks everyone. Any suggestions are welcome.
Ah, my bad, 3fe it is. :redface:
If you connected the wire to the oil sending unit to the tab on the side for the ground instead of the tab on top you'll fry your oil pressure gauge. When you fry your gauge it may initially read high then drop to very low and remain there.
I would install a mechanical gauge so you can monitor the pressure, I'm not sure of the specs. for a 62 but rule of thumb is 10 psi for every 1K rpm. Some newer cars can run on 4 psi at idle and this is factory specs.

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