Occasional 'no oil sound' at startup on 4.0 OHV. Why?

[RangerX]

It will sound like there's no oil in the engine. It happens maybe once a week, sometimes twice. Always when I go to start it first thing in the morning. Goes away in a few seconds. It's like when you do an oil change and then start the engine, those seconds before the oil reaches everywhere.
This is on my 93 Ranger, it's the 4.0 ohv, and it has about 350,000 miles on it. Stock engine, never any work or repairs on it other than intake manifold gaskets a few years ago.
One possible factor may be that it is parked pointing downhill, with a lean to the driver side. But I park that same way every night, so I don't know. Oil level can vary, but it did it this morning, and I had just added a quart yesterday, so it was full this morning.
Is this the sign of a oil pump going bad?

 

[RangerX]

Bump

 

[tdavis]

How old is the oil filter? Have you changed it lately? I believe it has a check valve in it, and it could be sticking.

 

[RangerX]

Changing the oil (and filter) is the one thing I'm good about. Every 3-4000 miles. Motorcraft filter. Plus the filter hangs vertically, open end up, so the oil can't drain out overnight...

 

[jd4242]

Sounds to me like its just taking a second for the lifters to fill up..you probably have rockers and pushrods that are starting to get worn down making the sound louder at start up.or worn lifters that are bleeding down faster now

The randomness is probably just depending on motor temp,outside temp and which rockers it stops on with its trying to open a valve..that will cause extra pressure and cause the lifter to deflate

 

[RangerX]

Hmm, interesting. I've seen pics in another thread of really worn pushrods, they looked liked whittled sticks. I don't know enough about engine internals to know in what way rockers and lifters can wear, but sounds like these parts don't all wear evenly?

I would guess that of the randomness factors you mentioned, it's probably what position the engine stops at, which lifters are up or down, which would be random. The engine temp is always cold when it does this. And by cold, I mean low 70s, which is the outside temp in the morning. There is no variation in that, it's always a few degrees plus or minus from 70 every morning here.

So is this a symptom of eventual catastrophic failure of any kind, or will this just get more frequent?

 

[jd4242]

Hmm, interesting. I've seen pics in another thread of really worn pushrods, they looked liked whittled sticks. I don't know enough about engine internals to know in what way rockers and lifters can wear, but sounds like these parts don't all wear evenly?

I would guess that of the randomness factors you mentioned, it's probably what position the engine stops at, which lifters are up or down, which would be random. The engine temp is always cold when it does this. And by cold, I mean low 70s, which is the outside temp in the morning. There is no variation in that, it's always a few degrees plus or minus from 70 every morning here.

So is this a symptom of eventual catastrophic failure of any kind, or will this just get more frequent?

Just get more frequent, eventually your start getting tapping wile running. Then it will be time to pull the covers and replace rockers and pushrods