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lost oil pressure, and STILL not sure why **UPDATE**

Discussion in 'The Garage' started by GMCLegacy, Jan 9, 2004.

  1. GMCLegacy

    GMCLegacy 1/2 ton status

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    ok bear with me while i explain the events....

    i took my truck out wheeling for a short trip, no problems with oil pressure at all.

    the engine was rebuilt about 2 months ago, the specs are
    1988 SB 350
    bored .030
    nothing special
    old cast iron intake w/ thermostat choke setup with my QJet.
    HEI
    high volume high pressure oil pump
    Autometer mech oil pressure gage


    as the story goes, the truck sat for 2 weeks while i was gone on xmas break at school. as i cranked it over, i looked the gages over quick and noticed the oil pressure gage was at 15-20 and sweeping upward. as the ole QJet works, it never runs after the first attempt. the second attempt was running long enough for me to see the oil at 40+ psi. on the 3rd or so try, it was begining to run on its own and i looked at the gage as it was at 20 and falling. i dont have a tach, but it reving around 2000. i shut the truck off and go inside since it was cold and didnt feel like messing with it.

    the truck had 10W30 in it, i check the level before i started the engine, it was good. it was barely above zero *F.

    the next day i pulled the distributor to to see if the oil pump shaft still existed. i took at scewdriver and turned the pump by hand, and within 6 turn i saw oil moving up the oil pressure gage line. i looked at the dist. and i found that on the end of the dist. where the oil pump engages, i could see where the two became seperated and were not spinning together (dist. was spinning but the pump was not). the cam gear does not look bad from what i can tell by looking down through the intake, and the dist. has 2 different patterns on it, one considerably lower on the gear than the other. although the dist. was used in my previus engine.

    so the question is what caused this to happen. i am afraid to just put it back together and have it work again, i would like to be able to let it run in the woods for hours on end without having to stare at the oil gage.
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: lost oil pressure, and not sure why

    wow, I've never heard of such of a thing... The only thing I can think of is was the hold down clip good and tight or did it get left loose last time the motor was timed or something? Maybe the bearings are worn out in the distributer and letting the shaft move around???? Did you inspect the dist really well, is the gear nice and tight on the shaft? whole shaft spin freely and no play? I am stumped besides those obvious things. /forums/images/graemlins/thinking.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/confused.gif
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: lost oil pressure, and not sure why

    Your oil pump driveshaft has a STEEL sleeve, right?

    Are you sure the four bolts that hold the oil pump together are tight?
     
  4. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    the dist. shaft that the gear is pinned to has about an 1/8" movement up and down. the gear is tight on the shaft

    i have a metal sleeved oil pump shaft

    today i used a priming rod with a drill, and got over 30 psi of oil. if those bolts were loose, wouldnt all the oil just dump back into the pan? im trying not to pull the pan at this point due to cold weather without a garage to fit the truck in.
     
  5. lukebaby1

    lukebaby1 1/2 ton status

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    Re: lost oil pressure, and not sure why

    With a high volume high pressure pump, and a fresh rebuild you should be pushing the gauge way up there around 100 when cold. Stock gauge should peg out. Sounds like one of three things. 1. Oil pump bolt has worked loose, 2. Oil pickup has come off of Oil pump and fell to bottom of pan.
    3. Cam is walking forward in bearings, (this would also account for big drop in pressure) and disengaging distributor shaft. (not good hope not). I would definitly drop the pan and take a look before major damage results. /forums/images/graemlins/shocked.gif
     
  6. mudjunkie 82

    mudjunkie 82 1 ton status GMOTM Winner

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    Re: lost oil pressure, and not sure why

    [ QUOTE ]
    Your oil pump driveshaft has a STEEL sleeve, right?

    Are you sure the four bolts that hold the oil pump together are tight?

    [/ QUOTE ]I think Tim is right,I would pull the pan and check the pump......
     
  7. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    im headed out to pull the pan, i will post what i find
     
  8. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    i pulled the pan to find the oil pump still torqued down to the block. the four bolt holding the pump assebly where also still tight. i pulled the pump off, and took the pump apart. the gears are polished with no scratches or chipped metal. the oil pump shaft (metal sleeved) is in one piece with no sign of wear on either end.
     
  9. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    lukebaby,
    i only normally will get over 80psi on cold startup, i was not spinning the drill at full speed, at the time i was just hoping for some oil pressure.
     
  10. lukebaby1

    lukebaby1 1/2 ton status

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    Re: lost oil pressure, and not sure why

    Ok, well next, I would take a good look at the distributor. Check the shaft for up an down play (should not have alot maybe a 1/16 or 1/8th. Also look for side to side up top with the rotor. Does the inside of the Cap look OK? If all that checks out, take a long screw driver and carefully see if you can push the cam forward any. If so then you may want to consider a cam button installed under the timing cover. Other than that the only other thing that would cause a loss of pressure like your describing is a bearing loosing its sealing integrity somewhere in that assembly. Since you already pulled the pan, you might want to try another Pump. Also if that distributor has over 75000 miles on it, I would definitly look at replacing it. Good luck! /forums/images/graemlins/confused.gif
     
  11. Confedneck

    Confedneck 3/4 ton status

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    Re: lost oil pressure, and not sure why

    cant crank/cam bearings going bad cause a loss of oil pressure?? i thought i remembered hearing that somewhere..
     
  12. lukebaby1

    lukebaby1 1/2 ton status

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    Re: lost oil pressure, and not sure why

    Definitly, you bet. /forums/images/graemlins/grin.gif
     
  13. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    at this point i do not think it is a bearing problem. for what it looks like to me that somehow the dist. and oil pump haft became seperated, causing my loss of oil pressure. i will look at the dist. more when i get back from work.

    thanks guys for all your help
     
  14. lukebaby1

    lukebaby1 1/2 ton status

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    Re: lost oil pressure, and not sure why

    You said that the bottom of the distributor shaft showed evidence of not mating properly with the oil pump shaft. If there was alot of play in the shaft (up and down movement). This would most certainly be evident inside the distributor cap. (gashes and big time wear on the contacts, rotor damage). The cam when turning would have a tendency to push up on the rotating distibutor shaft. /forums/images/graemlins/eek.gif
     
  15. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Re: lost oil pressure, and not sure why

    If the cam were walking enough for him to lose oil pressure it'd smoke cam bearings and jump time if I'm not mistaken.

    There are only a few things my Dad and I have been able to come up with:
    1. Smoked bearing somewhere, he's leaning towards cam bearings or main bearings. Marc, did you guys replace the cam bearings? My Dad was wondering because not a lot of people have a cam bearing installation and removal tool. I figured at least one strange ranger would have one.
    2. The intermediate shaft is a crappy one and is too short for full contact with the distributor gear. When a lot of load is applied to the distributor gear the distributor shaft lifts up off the intermediate shaft.
    3. A piece of something stuck the oil bypass in the pump open.

    This is what we came up with:
    We figured that if you measured from the top of the intermediate shaft to the top of the intake and then measure from the intake mating surface on the distributor to the drive in the distributor gear and they didn't interface by enough then that is your problem.
    Since you already have the pan off, pull the main caps off and and have a look-see.
     
  16. lukebaby1

    lukebaby1 1/2 ton status

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    Re: lost oil pressure, and not sure why

    I'm with Cyber, check the length of your oil pump shaft. Could be to short. /forums/images/graemlins/confused.gif
     
  17. GMCLegacy

    GMCLegacy 1/2 ton status

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    Re: lost oil pressure, and not sure why

    the member formerly known as wrathorc - i replaced the cam bearings, not personally, but the machinist in l'anse did for me.

    the shaft is laying right here, anyone have a dimension for it?
     

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