lost oil pressure

[dak605]

I installed a professionally rebuilt 4.3 engine in my 95 Blazer, including a replacement oil pump. Warmed the engine up until thermostat opened (195), oil pressure fine. Went to road test, shortly pressure dropped to danger area. Would go up momentarily with a little increase in speed. Engine temp normal. Removed oil pan to inspect. The pickup tube and screen were connected to the pump. The distributor turned the shaft operating the pump. Removed the pump, ran it with a drill. It pumped oil but when I increased the speed of the drill,I could barely hold onto the pump because it was vibrating wildly.

Should I assume the pump is defective even though it seemed to pump oil and replace it? Any other suggestions as to why I could have no oil pressure?

Thanks dak605

 

[427Z06]

Possibly a sticking pressure relief valve in the oil pump.

 

[Quest]

Obviously, there's a mechanical issue with regards to your "professionally" rebuilt engine.

While I would not speculate whether this has something to do with your new oil pump (possibly so), you'll be better off check back with the mechanic who serivce/RE-RE your engine to find out more.