I have a 93? Hijet that needed rod bearings when I got it. Pulled the pan and noticed the pickup tube is in the front and pretty high off the pan. After it was back together, I took it out for a drive and that's when I noticed the oil light come on trying to climb a fairly common hill. Is this typical? Also I noticed the Subaru sambar has a backwards facing rear engine.... What does it do when the oil is sitting on the Pistons climbing a similar hill? Probably going to sell the hijet for an acty. Oil pan design looks more slope friendly. What's your $.02?
I’ve putted my Hijet up some pretty steep stuff without any effect on the oil pressure. So, it isn’t normal. Had anyone else been into the engine before you? They might have forgot to reinstall the basket filter if there was one. Just guessing, as I’ve never needed to get that far into the engine on mine. I’d look at the oil pump, or the oil bypass valve. The pumps do wear, and the bypass valve spring can weaken over time.