Lost oil pressure

[todd619]

I was driving along listening to the radio when between songs I thought I heard a different engine sound (I always do that). Anyway, I looked at the gauge cluster and noticed the oil pressure gauge reading nothing. It was pegged as far back as possible. I quickly pulled over and shut off the engine but I didn't really here any worse clattering before doing so. The engine was still running smoothly and the temp. gauge (after market) didn't go up.

So here's my predicament: Is the sending unit out or did the lower fuel pump go out and I just happened to look down at the right time before there was damage? How can I test the oil pumps pressure without starting the truck so I know if it is just a sending unit problem. I've noticed lately the guage moving with slightly varying pressure depending on the engine speed which makes me think it's just the sending unit but I can't afford to chance it and mess up my motor. It's only got a little over 249,000 miles on it. Any ideas are appreciated.

[Southpaw]

Well, I don't know what year your truck is, but I used to have a 97 7.3. I don't know if the newer bs are the same, and I am not a mechanic but this is my experience with losing oil pressure.
I got my oil changed, the plug got stripped, and I got 11 miles down the road when it fell out. The truck shut off. I got out in time to watch the last 2-3 quarts drain out of the oil pan. No damage what so ever to the motor. There is a saftey feature in them, that if you lose too much oil pressure, the PCM will shut off power to the injectors, thus shutting down the motor.
So, in my "opinion", you should be able to start your truck up without worrying about doing any damage to the motor. If it is losing oil pressure, and it is not the sending unit, the motor should cut off before it hurts itself.
C'mon guys help me out here-is that correct on all of these motors?
Hope this helps!

[vitalidle]

What year is your truck? If you lose your low pressure oil pump it can no longer feed the high pressure pump and your truck would shut down.

[SCUFFY828]

IF THE ENGINE IS RUNNING , YOU HAVE ENGINE OIL PRESSURE , THE WAY THESE ENGINE WORK , IF YOU DONT HAVE BASE ENGINE OIL PRESSURE IT ISNT FEEDING THE HIGH PRESSURE OIL SYSTEM SO THE ENGINE WOULDNT EVEN RUN, IF I HAD TO GUESS I WOULD SAY THE GAUGE IS THE ACTUAL PROBLEM ,MAYBE SENDING UNTI , BUT BY WHAT YOUR DESCRIBING , IT SOUNDS LIKE A GAUGE PROBLEM

[todd619]

Thanks for the tips. I'm thinking it's gotta be a gauge problem too. If there was no oil pressure the needle wouldn't be all the way to the far left, right? It would be at the red mark I think. I had forgotten about the cut off feature with oil pressure. We had an '01 at my old job a guy ran low and it wouldn't start one day due to lack of oil.

Mine is a '95. It kept running after I noticed the neddle drop so I knew the HPOP was working but if the low pressure feeds the high then it has to be ok too or it would die sounds like.

Does anyone know where a good resource is to find manuals that actually cover the engines in these trucks? I easily find them covering the bodies with gas engines and an occasional nod to the diesel or the diesel books I find are scarce in useful information. I've looked on ebay but have a hard time trusting that what is being sold contains useful content.

Thanks again for all of the info. I'll hook an auxiliary gauge to it tomorrow and fire it up. Hopefully that's all it is and I don't blow my motor.

[alabamafrog]

I don't know about the 95 but my 99 gauge is not really a gauge, it is an idiot light that looks like a gauge. The sending unit it either on or off at around 9 psi so the gauge either reads no pressure or in the middle of normal not matter what the pressure is as long as it is above 10 psi. I have installed a real gauge above my mirror because of this design.