Question about 1993 GMC Sierra C3500

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No oil pressure. Can not locate the oil pump & the oil pump drv

Would like to find a schematic to download if possible.

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  • stebeck57 Jan 11, 2009

    Okay, that helps but can you tell me what drives it? I think that is where the problem lies. It doesn't have a distributor.



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The oil pump is Inside the Oilpan. The best solution to your Problem for a Schematic is to Get a Haynes or Chilton Manual at your Auto Parts Store Or at their Websites. I Purchase 1 for Everything that I purchase. They give you the Exploded views for Everything that you need to Fix.

Posted on Jan 11, 2009

  • Travis Humphries
    Travis Humphries Jan 11, 2009

    There should be a Sending Unit for the Oil Pump. I am not sure where it is Located on a 93'. My 95' has the Electronic Oil Pump and I have a Relay for it in the Fuse Distribution Box under the Hook. Check there first. Could very well be a Similar or Same Setup. Let me know.



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First, you need to make sure there is the proper amount of oil in the crankcase... so check the oil, add if needed, then see if the problem persists.

If so, verify that there actually is a low il pressure condition and this is not just a faulty indication. If you have a mechanical oil pressure gauge, we'll assume it is accurate... but if it is electrical, you will need to obtain a service pressure gauge. When you have this, remove the oil pressure sending unit from the engine block, and with the right adapters, fit the service gauge to the sending unit hole... then check the oil pressure situation with the more accurate service gauge. Note if the low oil pressure is only at idle, or if it persists throughout the RPM range.

If the low oil pressure clears at RPM, you probably have a problem in the oil pump (worn) or oil pressure relief valve (stuck), but that is usually a part of the pump assembly.

If the low oil pressure is persistent throughout the RPM range, the possible causes still include the pump but also take in loose crankshaft main or rod bearings or possibly an internal leak in the pressurized oil galley circuit, such as a lost galley plug (metal plug used to close the hole where the internal oil passage was machined/drilled). And there are other possibilities...

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Hope this is illuminating and helpful, and good luck with the problem. Do not hesitate to post further questions or comments an let us know how it goes...


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