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Oil pressure (lack there of)

Discussion in 'Early CJ5 and CJ6 Tech' started by jph0913, Oct 27, 2003.

  1. Oct 27, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    22
    I finally got my m38a1 running again after sitting for about a year, but I noticed that I was getting very low oil pressure at idle(the needle just barley moves off of the peg). I took the oil pump apart to see if there were any foreign objects in there, but it looked fine. I primed it and fired it up, but still at idle it has around 1 lbs of pressure, adn at around 2k RPMs it has about 10 lbs. As a side note, the last time it ran, the oil pressure at idle was around 8 to 10 lbs. The motor has been rebuilt and not used very much since I installed it. Any ideas on whats causing this problem? Oh its the F-head.
     
  2. Oct 27, 2003
    javracer

    javracer Land Locked Bubblehead

    Northwest Arkansas
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    Feb 4, 2003
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    I don't know much about the F-head but, the great Late Smokey Yunick preached that, "10 pounds per 1000 rpm is good for any gasoline engine." I guess I missed alot buying a early CJ5 with a Chevy siezed 305 between the rails. :(
     
  3. Oct 27, 2003
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    Can you trust your gauge ? electrical or mechanical ? I would think at the readings you are getting, you should be hearing valve train clatter or other noises.
    That being said, you need to look at a lot of things.
    Oil pickup in pan, bolts loose or no gasket ?
    Wow, the list can go on from there !
    Good diagnostics needed here :shock:
     
  4. Oct 27, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    There is chatter and other knocking noises coming from the motor. The gague is fairly new, but by hearing the motor knock it kinda rules out the gauge. I'll drop the pan and take a peek. Anything else I should look at while i have the pan off?
     
  5. Oct 27, 2003
    budtoh3zo

    budtoh3zo Member

    little...
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    Mar 23, 2003
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    can a dirty oil filter have anything to do with it? Just a idea
     
  6. Oct 28, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    The motor has 0 miles on it and maybe an hours worth of running. I did not do the rebuild, a local performance shop did the work. The only thing that chagned recently is the placement of the motor. I had to lower it, and shift it to the right. i did check the oil level, and it looked about a quarter quart low, but i never filled it all the way up.
     
  7. Oct 28, 2003
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Nov 6, 2002
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    4,275
    My flattie had a really tired L-134 in it when I bought it, and it too had really low oil pressure. IIRC, a new oil pump only cost about 40 bux and it brought the pressure up to about 20lbs at idle, and 50lbs or so at higher RPMS. Not a substitute for a new engine I know, but it may help you prolong the inevitable for quite awhile!

    Just a thought; Have you checked the pressure with another guage? How about the oil itself. Have you changed it lately and made sure you have 30 or 40 weight in it? Prior owners have a habit of doing strange things to vehicles. For instance, my jeep had ATF in the T-90 so it just about ate itself to bits... :rofl:

    <EDIT>

    Disregard my comments on the tired engine. Your last post came in before I could type in my response. :oops:

    <END EDIT>
     
  8. Oct 28, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    I spoke with a friend of mine, and he suggested that I replace the oil pump to go with the rebuild, which does make some sence.
     
  9. Oct 28, 2003
    Brian45

    Brian45 New Member

    Hermosa, South...
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    I personally think that I would tow it over to the rebuilders and have them check it out, just a thought
     
  10. Oct 28, 2003
    Ducks-Bass-n-Jeeps

    Ducks-Bass-n-Jeeps A Parade of One

    Brentwood, Tennessee
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    Aug 11, 2003
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    I just rebuilt my F-head. And the idiot light comes on at idle when the engine is at operating temperature.

    :hurrican:
     
  11. Nov 1, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    I checked the oil pick up and it is tight and a gasket is there. But when I drailed the oil, there was a vey strong gas smell. Fresh oil and tried again, and the pressure is still low, and some knocking noises from the motor. Im running Castrol 10W30, is that too thin of an oil? Should I be running something thicker liek 10w40 or maybe 20w50?
     
  12. Nov 1, 2003
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    Where I live I use straight 30wt. This may not be suitable for colder climates. The gas odor is interesting; flooded from trying to start the engine, or maybe a fuel pump that might be leaking internally and pumping fuel into the crankcase. There are still so many possibilities, but only a few more that you would be able to check. As was suggested before, maybe a trip back to the rebuilders. If any of the machined tolerances are out of spec, there goes the pressure no matter what you do.
     
  13. Nov 1, 2003
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    jph, I've done a little reading about the 134 lately. Maybe I can suggest something that could be of help.

    - there are a few pipe plugs that have to be put back in the oil passages when the engine is rebuilt. They are shown here: http://www.film.queensu.ca/CJ3B/Engine/Rebuild2.html

    - this page has some tips about oil pressure: http://www.film.queensu.ca/CJ3B/Tech/OilPressure.html Note that the oil pressure can be adjusted by changing the releif valve pressure.

    - seems to me that a rebuilt engine deserves a new oil pump.

    - I understand that the L and F 134 only have one cam bearing next to the timing gear, and that the other two bearing ride in the block. I'd think that this could be a problem in an old engine, and remember reading something about this problem long ago.

    - usually gas in the oil comes from a fuel pump leaking into the block.

    - nothing against the group here, but I'd think that the guys over on the G (g503.com) would be another good source of 134 info.

    hth 8) Tim
     
  14. Nov 1, 2003
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I guess you're saying the engine sounded fine, didn't knock during the original hour or so you ran it a year ago? And the oil pressure was good? When rebuilt was the block cleaned? Could be the pump, but it also sounds like something got plugged, stopped up.
     
  15. Nov 1, 2003
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    The engine has been flooded several times due to carb problems which have been fixed. The fuel pump is new so i doubt it is leaking. After the motor was rebuilt, it did have a knock, but and the oil pressure was a little low, around 10 to 12 lbs at idle. I dont think that taking the motor back to the guy who rebuilt it is an option b/c any warrenty has expired, and I dont want to pay someone to fix it unless I have to.

    Thanks for the link Tim. The two plugs near the crank are plugged, and the freeze plug for the rear cam bore is installed. I'll order the oil pump tomorrow.
     
  16. Nov 2, 2003
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    On the front of the block there is an oil jet designed to spray on the timing gears. This makes me wonder if it was left out, or loose? Also, on the earlier engines the orifice was too big and caused the front main bearing (I think it was the main) to starve, so they made a jet with a smaller orifice to fix this. I don't think it caused an overall low pressure problem though. You would have to pull the timing gear cover to check this out.
     
  17. Jun 16, 2004
    jph0913

    jph0913 New Member

    Raleigh, NC
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    Aug 6, 2003
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    Update.. I replaced my oil pump finally, still low oil pressure, and a knock. Any ideas on what the problem could be? Im really at a loss....
     
  18. Jun 16, 2004
    CT

    CT Member

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    Change your oil to get any gas out it, and drive it for about an hour. The rings have not set yet. I bet it picks up oil pressure, and if it smokes, it should stop smoking

    How much did an engine rebuild cost? Just wondering.

    Thanks
    Cliff
     
  19. Jun 17, 2004
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    A tip for the knock
    one way to determine which cylinder might be involved would be to run the engine at idle (knocking) and remove 1 plug wire at a time. If it is piston, wrist pin, or rod bearing involved, good chance the noise might disappear on the suspected cylinder when the plug wire is pulled of the plug. This makes the plug not fire and reduces the downstroke pressure on the cylinder involved. If the cylinder stops making noise when the plug wire is removed, you now know which cylinder or rod to look at when you drop the pan. If bearing related, could be the source of your low oil pressure.
    The rings seating/ not seating wouldn't have any effect on oil pressure.
     
  20. Jun 17, 2004
    jph0913

    jph0913 New Member

    Raleigh, NC
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    I will have to try that. I know it is coming from either #3 or #4 not sure which. What should I be looking for, the inner workings of a motor are still new to me.
     
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