rebuilt 7.3 not starting no oil pressure HPOP not staying filled

[breakstuff]

I have a 2000 f450, pulled out the motor due to hole in #8 piston, put in a '99 long block. Double checked all wiring connections, all hose connections, filled head galleys, filled HPOP. Cranks fine, no oil pressure building, HPOP drains into crank case after every attempt to start. no smoke when cranking. no leaks anywhere. i have cranked 30-40 times at about 1 minute each time. when i reinstalled the HPOP, i used the same type of gasket that came out of it with the screen.

please help me to get this started

[JSchuricht]

You may have the wrong gasket. I have done a few and there was no screen.

[jc82chevyman]

IIRC there is anti drain back in the reservoir to prevent that from happening

[breakstuff]

I have read on the gaskets and as long as you put in the same one that came out, it is okay.

Where is this anti drain back?

[Codum]

Double check to make sure you tightened the nut under the front cover of the hpop above the water pump properly. I have had this issue, after I scratched my head a few days I checked it and it was loose. I know I tightened it but it was loose.

[Solid98]

No oil pressure while cranking and an empty HPOP res tells me to look at the low press oil pump.

[Codum]

Originally Posted by Solid98

No oil pressure while cranking and an empty HPOP res tells me to look at the low press oil pump.

He said the hpop resivoir drains after every attempt to start, the fact that it drains means it is getting oil pumped into it from the low pressure oil pump. I am not sure how he knows this unless he has opened the resivoir plug while cranking. If not I would, open the plug while cranking and see if oil starts to run out, if so its not the low pressure oil pump.

[GAS]

The antidrain back check ball is in the block on the later trucks.
On the left side of the very front of the block just below the head block joint.
If memory serves correct, its a largish allen socket plug, assembly goes, plug, spring, check ball.

[Codum]

Did you get it running? What was wrong?

[52d2]

my truck dose the same changed the lpop no difference i've pulled the anti drainback ball a few times but what im wondering now is if its supposed to seat on an o ring in the hole it looks like theres a shoulder for one im scared to try it in case it gets sucked in deeper somewhere