I am so stuck here.
I start up my truck i have oil pressure i drive it around for a while engine heats up i pull up to a stop sign and/or have it in park and oil pressure plummits to Low and Check Guages light comes on.

Changed Oil Pump this weekend and filled fluids today started up seemed fine then same problem again no oil pressure at idle.

While I had the oil pump off i sprayed a can of break fluid down the pick tube and forced air to make sure nothing was clogging the pick up tube.

What else can be the problem, I already replaced the oil pressure sending unit.

 

Have you hooked up an oil pressure gauge to any of the oil lines to make sure you actually have low pressure?

It's possible you have another bad sending unit....

If you are getting low pressure at the sending unit when you test it, you might want to hook up another gauge at the oil filter (they make special brackets to do this) and check it there as well.

If one doesn't read the same as the other, then you might have a clog in the system.

The other possible cause is that your oil pick-up has a crack in it somewhere causing you to lose pressure at idle...

You need to do more investigating with real gauges, b/c the OEM oil pressure gauge is not always accurate.

 

Could also be worn internals.

 

I dropped it off at the shop today and am having them change the oil pickup tube and o ring along with the oil pan gasket i had these parts already and was planning on doing them soon, but do not want to keep driving it like this.

I did more research when I got home today online and am pretty convinced when I did my head gasket recently and repaired some bent valves that maybe it is something with the cam bearings this makes the most sense to me I am also got the check engine light a few times stating intermittent cam sensor error.

When I had the cam off I made sure I put all of the cam bearing caps back on in same order with arrow facing towards me, but now im thinking more and more this is the problem.

If this is the problem what can I do the bearings are not serviceable I can get a new cam for $145 on ebay but not sure what to do about bearings. Or do I just chance it and get a used cam and bearing caps from junk yard?

This truck had almost 300K miles on it but runs like a brand new truck besides the dam low oil pressure problem after it warms up at idle.

 

Well you should ALWAYS replace those bearings when you take them out... as you'll never get them in the same place as you did before.

Did you check all the bearing clearances?

Anyways... you dropped it off at a shop, so let them tear into it and see what they find.... if you aren't leaking oil, and the level is where it should be, the only other options you have are:

1) Obstructed Oil Flow somewhere in the system (includes clogged jets, passages etc.)
2) Bad Oil Pump (not likely since you replaced it w/ a NEW one right?)
3) Broken or Damaged Oil Pick-Up

 

From what I was reading yesterday it sounded as if the bearing clearences are too much then it will never build up pressure as it will just spew out of the top instead of being pressurized.

 

that's why I asked if he had checked the clearances...

I'm sure the shop will figure it out... I just hope the bearings didn't get screwed up b/c of bad clearances, that won't be fun (or cheap) to fix.....

 

Heavier weight oil will help lengthen the lifespan and bring up your pressure for worn internals.
If your oil galleys are clogged up, this will reduce oil passage drain back and could reduce flow therefore causing lower pressure. If you put in heavier weight oil with this problem, it will only exacerbate the issue.

I have seen aftermarket sending units bad out of the box. They have far less quality control and use lower quality components. So, this means your pressure could be off by as much as 10-20% by a low quality part. Resistance values start to walk from actual value the hotter they get, so it would make sense that it goes faulty when hot and not cold.

You can test the sensor by putting it in a boiling pan of water and verifying it's resitive values. The service manual will tell you what they need to be at.
I'd try 10w-40 and see if that helps out. If not, you might have to go up to 15w-50.

 

Yes it will -- and only temporarily as the wear won't stop and eventually you'll need a rebuild anyways. But if you need the truck and something do drive, do your thing.

 

Is their anything i can do without replacing head, if i was to put a low mileage used cam in with its matching cam bearing caps would that help or probably not because the issue is more likely with the lower cam bearing built into the head.