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Oil pump

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Adub, Dec 20, 2004.

  1. Adub

    Adub 1/2 ton status

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    Tried to search this topic, only one thread came up.

    Finally got the flexplate replaced on the truck. After sitting for a couple months, it fired right up, but I noticed Oil pressure was at 0. I immediately shut it off. Checked my sensor connections, everything looked good and the gage used to work. Pulled the dr side valve cover and fired it up for a sec. Sure enough, no oil. I've never replaced an oil pump before. Parts store sells them for 16 bucks or something. Anything tricky? I figured Id pick up a Chilton's manual.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    You are going to have to update this one when you get finished.

    I've never heard nor seen a pump that has gone so far as to move no oil.

    These are gear on gear pumps, it would be almost impossible for them to pump NOTHING...I've seen one with dents in the pump rotors from engine schrapnel going through them, and big gouges where the rotors sit in the pump, but there was still oil pressure.

    In my mind, it's likely that the distributor has a problem. I guess the piece on the pump that is turned could break the ears off if the pump seized from something getting into it too. You might want to pull the distributor before buying a pump, it might be on that end. Once the dist. is out, and with a long flat blade screwdriver and some patience, you can see if the oil pump turns, if there is evidence of a problem on the end of the distributor. Probably going to be a good idea to drop the pan anyway, no way of knowing if the pickup is clogged from something as well.

    If people use a lot of silicone in the wrong places, it could end up blocking the pump pickup too, as well as coked up oil making it's way down there. My old 305 had a layer of that stuff that if dislodged, could easily have blocked the pump pickup.
     
  3. Adub

    Adub 1/2 ton status

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    Well, it registered a solid 60 psi before I shut it down for the flexplate ordeal. Now nothing, no oil making it to the rockers. Guess Ill just have to tear into it.
     
  4. k20

    k20 3/4 ton status

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    dont risk it by runnin it, just thinking out loud, that perhaps the oil pump lost its prime? Like our fish filter, you let it get empty, it takes forever b4 it starts pumpin again.
     
  5. dremu

    dremu Officious Thread Derailer Premium Member

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    Jah, I seem to recall reading about priming the oil pump with an electric drill and a really long screwdriver bit. Never done it myself, mind you.

    -- A
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    On an initial engine rebuild, or after a LONG time sitting, it is recommended to prime the engine, but thats to get oil into the block, not for the oil pump, since it will drain every time the engine is stopped if the oil level is below the gear section of the pump, which I believe it always is. Either way, it's either always already in oil, or always empty on engine startup.

    Dunno how long it would take with some running to register pressure if the pump was working, but it has to be prety quick...how many peoples vehicles sit for months and start up with oil pressure coming up almost instantaneously?

    You can't prime a Chev with just a drill, you need the distributor housing (or equivalent) in place to oil both sides of the engine.
     
  7. 86dieselburb

    86dieselburb 1/2 ton status

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    Is your motor stock? If so you may have a broken oil pump shaft coupler. Chevy in its infinite wisdom used nylon for the couplers. When you replace your oil pump, do yourself a favor and replace the oil pump shaft with a solid steel shaft. Does away with that cheesy coupler. It's a little added insurance and it can be replaced at the same time as the oil pump.
     
  8. Adub

    Adub 1/2 ton status

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    As far as I know, the engine is stock.
     
  9. sweetk30

    sweetk30 professional hooker Premium Member

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    check this

    i would remove the press sender and install a manuel gage and fire up and watch for press seen many senders go bad!!!! replaced o in my truck was working o.k. but seped oil from elec plug and i got almost 10psi more on the gage. some sbc take 20-30 sec to get oil to the top after sitting a long time. the lifters need to a fill back up. try this gage test first to save your self a bunch of time.
     
  10. Adub

    Adub 1/2 ton status

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    Where would I find this gage? I called O'reilly's and they said they don't sell them. Couldn't find one on Harbor freight either.
     
  11. POWERMAD

    POWERMAD 1/2 ton status

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    El Cheapo manual gages work well for a test gage.
    Even if it sat for a long time it should build pressure in a few seconds.
    The oil filter is still full and the pump is already primed.
    With all of the engines I fool with that have sat for a long time it generaly takes a bit of cranking to get em to fire at first and pressure has always come up before the engine fired.

    I would definately verify 0 pressure before tearing into it.
    A cheap gage from wally world would have the line and fittings too.
    Snap On and such have pressure gage sets but are pretty pricy.
    I made my own set with stuff I have collected over the years.
     
  12. motorheadnelson

    motorheadnelson Registered Member

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    Yup sending units go bad. Mechancal gauges are the way to go. Oil pump pressure relief could have a tiny piece of crud in it, holding it open enough to register 0 psi at idle. (Been there).
     
  13. bigblock44k5

    bigblock44k5 1/2 ton status

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    Go to your local auto parts store, they will have cheap guages in the performance section you can swap in to check. You can also check the guage by pulling the wire off with the key on, the guage should peg all the way high, if you ground the wire it should go to 0. If it still shows no oil pressure with a new guage, check the oil system. Make sure there is oil in it of course, and pull down the filter and dump it out to check for sludge that might be blocking it. If all this looks alright, use the drill priming method to check for pressure. If none of this works give us a new update.


    BTW-After an engine sits, even overnight, it will take a little while before oil comes up through the pushrods.
     

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