Ok so to start off with I'm by far no ford guy. I had a guy ask me to replace his zf5 with a reman. Glow plugs. And the oil cooler. Well all went well. Except when I went to start it. It fired up then died. And no restart. Checked The hpop for oil it was empty. So we primed it. It fired up ran for a bit then died. Then we realized it had no low oil preasure. This is through the factory gauge and an aftermarket manual gauge. We then rechecked the oil level. It was full. Checked the hpop its empty. Refilled the hpop thinking maybe just didn't have time to refill the oil system beings we drained it all. Ran with no lop then died. I then checked the oil filter to see what the level was because when put the new filter on I left it about 1 1/2" down from the top. It was full so I know the lpop is pumping. But why do I not have any low oil pressure. And the hpop keeps being drained as soon as it gets cranked or starts. I was thinking the ipr valve. Let's hear your thoughts. Thanks a lot.