Oil Guage Or Pump Faulty?

[Grillmaster]

A little background, I just did the timing chain replacement on my 2003 4.0 190k mile explorer. Have about 20k on the new timing chains. Driving at 60mph my "check guage" light went on and oil pressure guage bounced around a little then went to 0. I pulled off the freeway and when I put it into reverse Guage showed pressure. I noticed the belt tensioner was bouncing slightly and sounded like it was making some noise. I got back on the freeway and drove it for another 20 miles then guage showed no pressure again. I kept driving (thinking it was a faulty sensor) and started to hear some engine noise so pulled off again. Got it towed home and just started it again and now it shows oil pressure on the guage. Thinking I need to:

Check/replace tensioner

Replace sending unit

Check oil pressure with a mechanical guage somehow.

Replace oil filter

My question is if there was no oil pressure shouldn't I have got a low oil pressure light. And if there was no oil, would it have ran for 20 miles? How do you check the pressure with a mechanical gauge?

Any thoughts and ideas would be helpful. Have a lot of work in this truck already. Pulling the engine again is not going to be an option.

 

[Joe in NY]

The CHECK GAUGE and oil pressure gauge reading 0 PSI is the no oil pressure indicator! There is no additional oil pressure light to say: "HEY, YOU HAVE NO OIL PRESSURE. STOP DRIVING!"

I have a small hate for Ford using a 5 psi oil switch and gauge that just shows happy Normal pressure or 0 and you're f*cked instead of a sensor and an actual gauge that is meaningful. An engine will not be happy at 5 PSI of oil, yet Ford seems to think so. Was driving a car with DOD and a lifter was coming apart which caused the oil pressure to drop from the normal 40 PSI on highway to 15~20 PSI and 10 PSI at idle. Right then I knew that something was very wrong and knew what was wrong based off of oil pressure and engine performance. But if it were Ford everything would still be "Normal"........

 

[massacre]

So true
I installed a mechanical oil press gauge in a couple vehicles. Reading it while driving can tell you a lot more about what's going on with the engine than just oil pressure

 

[Drewmcg]

I've had a break in the wire (once) and a corroded/cracked sending unit (once) on these engines. Its hard to get that sucker back in the engine bay w/o whacking the sending unit! They cost around $15, IIRC. Check your wire integrity (single wire) and screw in a new oil pressure switch (lower front of engine, driver's side) before you freak out about oil pressure.

 

[Number4]

Why did you do the timing job originally?

It’s possible, if your OE guides broke, that they are in the pan getting sucked up and blocking oil flow. Then falling back into the pan when you turn it off.