Intermittent Low Oil Pressure

[AuroraGirl]

You can do actual diagnostics or you can guesstimate and radomly replace parts, and it's this evan though i replaced it with new. A blocked filter? As in never changing a filter or you engine is making some much debris in the oiling system? If the filter material no longer flows oil, it would in continuous bypass. Our oil filters are not full flow. Our oil filters are in bypass above a preset psi. Therefore a " blocked filter " would have no effect on system pressures. An oil pump showing it's age can have big effect on oil pressues. There are no seals internal. Just metal to metal clearence. As gears an surfaces wear those clearances open and pressure tapers off, and partial oil circles within the pump rather than pressuring oil system. Small areas of wear within the engine all add up. A half to one psi drop along the cam bearings, one psi at each main bearing. Wear on the pump gears and flat surfaces. A hot Calif day " what 10 psi ? ". The service states a minimum 6 psi at idle is acceptable. Good luck.

Who said blocked filter?

 

[Schurkey]

What oil pressure sensor(s) does a '90 have?

'87--'89 uses a small switch by the distributor to bypass the fuel pump relay. There's a fist-size canister just above the oil filter that sends it's signal to the dash gauge. Those canisters are known to be screwy; I've had four of 'em on my '88; and I don't know if the one on the truck when I bought it at 170K was original. I'm getting about 50K miles out of them. They can read "too high", "too low" or randomly high/low. Sometimes when you unthread them from the vehicle, they slosh because they're full of oil inside--faulty seals.

They are, in short, poorly designed/poorly manufactured junk. Apparently, one company makes them (in Asia, of course) and fifteen other companies buy in bulk, put them in custom boxes sold under whatever the "House Brand" is.

The defining item is the green paint on the end, at the base of the hex. (NAPA OP6729)

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Some parts stores catalogs show a different sending unit, but it's too big--won't clear the exhaust. (NAPA OP6649) Even tried it with different adapter fittings, but it just doesn't work.

http://hbassociates.us/K1500_Oil_Sender_02.jpg

 

[GoToGuy]

Who said blocked filter?

Beginning Initial post, second line from bottom.

 

[thinger2]

Oil pumps can get worn out but it is pretty rare.
Dont trust the factory OP gauge.
Install a mechanical oil presure gauge and see what is really happening.
Fix all of the ground wires too.

I have at least 4 different OP sensors on the shelf and I can swap them and get 4
wildly different results
They vary between check gauges and fluttering from 10 to 80 psi.
And the old factory one just drifts around at about 40 to 60.
What I actually have is now 60 at cold start and 40 running and 20 hot idle.
If I took the factory guage as truth, I would think It was done.
Dont trust your factory instruments at all.
They are pretty much worthless.

 

[GoToGuy]

Four different brands, four different applications, four different volt/ ohm range. " Don't trust your gauges ' they are pretty much worthless "
Do you propose we rip out all gauge packages and replace them with state of the art digital.
Couldn't there be some middle ground, not blanket statements that all factory are no good ?
How about testing, verify, system knowledge, operating conditions.

 

[Schurkey]

...not to mention "buy the sending unit that matches the gauge", and "Fix what's broken" in the gauge system.

You'll get screwy results if you use a 0--80 pressure sending unit on a 0--60 gauge. (or the other way around.)

Broken or bare wires make for no, or intermittent readings

Some gauges--fuel gauges, for example--have dampened movements; they're erratic when the dampening is broken.