Low oil pressure

You need to hook a fuel pressure gauge to it. It has to have 55 psi or it won't run. Have you checked for spark at one of the plug wires. I'm guessing low fuel pressure, fuel pump.

You may have a bad oil sending unit this is located under the hood near the oil filter two wires are connected to it. i would change this and see if your problem persists, if so you could have an oil pump you wont hear anything until its too late. 20 psi is all you need to keep it alive. good luck

have it tested using a manual gage if still low then main baring ore most likely bad that would mean a over hall if is really low and bearings bad should be making rattle noise when started up first few seconds

While engine is running, open the cover where you add oil to engine and see if you see a good flow of oil, if good flow, could be as easy as replacing oil sending sensor. got to realize that if poor maintenance history your engine may not be building enough pressure at iddle to move your hydraulic operated valves, only when you rev it up it will pump enough to run smooth. if running engine too long, you may cause more damage to other engine components such as crankshaft and cam shaft bearings. if you can spare a few bucks, have a good mechanic check your oil pressure with a mechanical gauge. another cheap option is to replace oil pump. last resort if you love your truck as much as we do,replace engine or rebuild it. At 205,000 this is a normal symptom, other than timing chain problems, most engines don't make it that far. hope this helps!

If you are using the gauge that came with the vehicle it's accuracy is not great. These gauges were designed so that at a glance you can see the needle is pointing basically to the middle of the dial. As long as the needle is more od less there, you're okay but the numbers mean nothing due to the gauges in accuracy. If you really want to check the oil pressure, the procedure is pretty easy but requires decent equipment as well as the knowledge of where to tap into the pressurized oil system.

Nope, normal on start up is 60 PSI and once warmed up drops to 45 psi. Have the oil pressure checked for a proper reading during start up's when the engine is cold. As for the lifters ticking, that may be a sign that the engine was ran with low oil pressure or no oil and the lifters are damaged, or low oil pressure and the lifters are starved of oil. Try not to drive it and have a proper oil pressure reading, low oil pressure will damage the engine by having the main crank bearing to spin which is a engine replacement. Good luck and keep me posted.

if it shows low oil level its possible bad "level sensor "located on oil pan.if it shows low oil pressure possible oil "pressure sensor"

could be one of two things, oil pressure switch (located on top of engine behind intake) or instrument panel cluster, if your vehicle has under 70,000 miles, it's covered under warrenty

30-40 psi of oil pressure is fine for many vehicles including your GMC. I am assuming that the truck has more than 100,000 miles on it and still has the original engine in it. By rule of thumb you only need 10 psi per 1000 rpms in a typical street driven engine to give adequate oil pressure to keep the bearings from oil starvation. The oil pressure is typically higher when initial start up occurs because it is more viscous due to the temperature of the oil as the engines oil warms up the visconsity thins out and the oil flows more smoothly. The drop in oil pressure is a normal occurance. Above 45 is more than required for a daily driven street engine. I believe that the specs on that engine only list 30- 45 psi.

Is this after recent oil change.Sound like you have the wrong viscosity of oil.