well, i'm working on a friend's truck ('99 Ranger Super Cab 4x4 with 3.0 and auto tranny) and for once, i'm kinda stumped. i'll take it from the top and see if any of ya'll can help. about 3 weeks back she ran it low on oil. i heard the valvetrain and checked the oil, wasn't even on the dipstick. she put oil in it and the noise went away...for a few days. checked the oil a few days later, still full...checked for leaks, didn't find any. well, here it is about 3 weeks later, she finally tells me i need to take it and try to fix it, as it has NO power and makes HORRIBLE valvetrain noise when warmed up. i figure it's a collapsed lifter or a bent pushrod-worst case a burnt valve. i pick it up and first thing i do is check the oil, it was about halfway within the crosshatch area, so it was ok. hop in, fire it up, truck sounds TOTALLY normal, no noise, running smooth. i take off, stop at the commissary (my wife and i needed to go grocery shopping, truck was on the way), about an hour later, we go to leave, truck still sounds totally normal (i noted on the way to the store that the temp gauge wasn't working right, and i thought that MIGHT be the valve noise issue, since the computer references signals from the CTS to adjust timing). as i get out of the gate i start to hear the valve noise. about halfway home (i only live about 6 miles from work-where i got the truck from) it starts losing power BAD and making so much valve racket it almost sounded like it had NO oil in it, but the gauge still said normal (no idiot light either). i had to stop at a light to go to my house, as i'm stopping it dies. took me about a minute or two to get it to start again, and when it did it had horrid valve noise and belched a LOT of black smoke like it had flooded (i thought at that point it might have been an ignition problem, too much fuel and a weak spark). it was also REALLY weak, and i barely got it to 30...it stalled again right before i turned onto my street...barely got it started again (bunch of black smoke again). it stalled a third time in my driveway...played with it, got it started, parked it. today i tried to start it, after it had cooled, sounded like it had NO compression, so i run a compression test...here are the results...

Cyl 1: 90 dry, 100 wet
Cyl 3: 60 dry, 90 wet
Cyl 5: 110 dry, 140 wet
Cyl 2: 85 dry, 110 wet
Cyl 4: 60 dry, 70 wet
Cyl 6: 125 dry, no need for wet test, cyl. within specs

by looking at that test, it looks like 5 cyls have bad rings. i find this REALLY hard to believe. this truck was running STRONG right before all this started. i'm leaning toward a couple blown head gaskets. this really doesn't explain the valve noise from what i can tell with my shadetree experience though. is it possible that it has BOTH issues-a bent pushrod/burnt valve/collapsed lifter AND a couple blown head gaskets, or does this thing REALLY have 5 cylinders with blown rings? the truck wasn't smoking before AT ALL and there is no water in the oil. but i have also seen head gaskets blow on vehicles and NOT mix oil/water at all. the truck did have the gurgling coolant issue before, which i DID mention might be a head gasket leaking...so, does anyone have an opinion on this before i start tearing it apart, or any more checks i can do to make sure before i start really tearing into it or tell my friend she needs a new motor/rebuild? truck is in pretty good shape overall and has 100,4XX miles on it...

thanks in advance for taking the time to read this and for any help you can provide!
Josh

 

Fuel in the crankcase will show as good oil level? If you have collapsed lifters, the compression readings will not be normal. If you can, do a leakdown test. A leakdown will tell you if you have a ring or valve problem.
When you did the compression, did you pull all the plugs at one time? I note the cylinder order... They mostly seem to pick up 30psi w/oil, almost, so they're about the same.
The gauge IS an idiot light on most late-models. There is a resistor in the circuit that 'tells' the gauge to go to the middle of its reading. Unless you have a true sending unit on the block. Most have an on-off switch that closes at 5psi. That, along with the resistor, make the gauge go to the middle. The switch will be about 1" in diameter, with a plastic or bakelite area, and one connector in the middle. The sender will have a dome-like shape, where a variable resistor moves in relation to oil pressure.
Get a cheapo pressure gauge from WallyWorld, and replace the sending unit for a test. Seems you are losing oil pressure, and if you had an injector leak, it could dilute the oil and try to lube the bearings with fuel. The black smoke indicates too much fuel. The power loss could be bearings starting to sieze or ...
How's the coolant temp? Can you turn the crankshaft over by hand, or is hard to turn?
tom