Hello, recently I have been having an oil pressure problem. I just bought the truck and the first this I did was change the oil (pitch black) to new full synthetic 10w30. My truck has 119000miles. I drove the truck 180miles with original oil with no problems. With the new oil after about 10 miles I came to a stop light and my oil pressure dropped to zero. I reved the engine to 1500rpm and it jumped right back up. This happened a few more times in the next 10 miles until I was able to part the truck back on campus.

I started by dropping the oil pan. There was a small bit of sludge in the bottom and a little sediment but no chunks of bearings. The oil pump screen was almost completely unblocked. I took the oil pump appart and there was nothing that I could see wrong with it (clearance was very tight and there was no scarring, pitting, or wearing on the gear faces). Still I replaced it and cleaned the oil pickup tube in a parts washer. I cleaned the oil pan including blasting and painting the outside. I reinstalled everything and filled it up with oil.

I tried to prime the pump by pulling the coil wire and cranking the engine for a few seconds, and got no pressure on the electric guage... I tried again and still nothing.. I was getting a bit frustrated so I started it and let it run for about 6seconds hoping this would spin the pump with enough speed to pump the oil. The engine sounded just like an engine with no oil it . It was really painfull listening to it run and I hope a few seconds without oil pumping did not do any damage!

Anycase I pulled the valve cover to check what the condition was and it was spotless. I could not find a speck of sludge which was good news I guess but I still didn't know what oil was not getting in. I started to pull the oil filter and after about 4 turns it started overflowing with oil so I know the pump is getting oil that far. I pulled the oil sending switch which was really a pain and cranked the engine and no oil came out of its port. Should Oil have come out of the oil pressure switches port when the engine cranks??

 

yes. oil should be pumping through all cavities.

it would take a couple of moments to fill up the oil filter, and another couple of moments to fill up the passages and lift oil to the sensor. but - within 20 seconds or so, oil should be pumping out the oil sensor port.

since you lost pressure before changing the oil pump, and the new oil pump didn't help, there must be a blockage somewhere.

i'd blow air into the oil pressure sensor hole.

 

I hooked up a mechanical oil guage and I am getting plenty of pressure but the engine sounds terrible I would say its knocking If I had ever heard another engine knock. I don't know what gives. Its also backfiring and producing a lot of smoke..