84 Jimmy 6.2 ltr deisel problem with oil pressure

A question for any of you deisel owners out there,
I have an 84 Jimmy with the 6.2 deisel and recently as I started it to warm up, my oil pressure suddenly went to zero. I emmediatly shut it off
but then after checking the oil level, ( good,) the pressure switch, (good) Ive determined that it is indeed a problem somewhere in my engine and am getting no oil pressure at all. Yesterday I pulled the pan and the pump and found everything to look normal, the drive rod is complete and not twisted or broken and the pickup filter/tube is clean. the pump itself is in ok condition. Any Ideas Where I need to check next? What drives the oil pump? Is it attached to the fuel pump drive? It still starts and runs. I dont have the detailed repair manual or schematics of this engine.
Thanks in advance
Dennis
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The camshaft drives the vacuum pump that is behind the intake manifold, then the vacuum pump drives the oil pump shaft.
You should have checked the oil pressure with a mechanical guage first.
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I did check it , Its a mechanical guage not electric, and reads 0 oil pressure. And did several other test to make sure it was not a fualty sending unit/ coupler or pressure guage. So if I understand you correctly, this vacume pump is located under the intake manifold? and should be where I go next?
Thanks Again
Dennis
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Geez the last thing you do is open the engine.... You say the pressure switch is good what do you mean by this... There is a pressure sender mounted on the block behind the drivers side head (looks like a 2" mushroom with one wire coming from it). Replace this and see how you make out. The chain drives the cam, cam drives vacuum pump and it drives the oil pump (same as the distributor in a gas engine). The engine runs so you know that it either is electrical (gauges - turn on ignition and ground out the sender wire, the gauge should peg), sender (replace should be ~$20) or the drive btwn the vacuum pump drive gear and the oil pump (pull the vacuum pump and check to make sure the gear is not bad). When it is all said and done I would bet the sender is bad. Since you have pulled the oil pump off the engine you need to reprime the engine like it was new. So you might as well replace the oil pump (incase it has a bad pressure spring) and replace the pan gaskets. If you don't know how to bench prime an oil pump post back. Working on the 6.2 is just like working on any other V-8 so the same concepts apply. Post back with more information if we did not help.
good luck, mark
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