No I didn't pull it to test. The pickup easisly unbolted from the pump, so I just did a swap. The used pump looked identical to the pump underneath. No damage to the pump was visible. Any ideas on why I would have oil pressure for 10 minutes, then none? This makes me think that the pump works OK if it can maintain pressure for that long. I am also suspecting the pressure relief valve may get stuck open & rob me of valuable oil pressure. Any thoughts on this? Thanks.

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1985 300CD 279k
2000 F250 powerstroke