1. 1978 cj5 AMC 304 no oil pressure

    We have a 1978 cj5 with an AMC 304. My husband and I have rebuilt our jeep. The problem is we will have oil pressure and then the next time we drive there will be no pressure. We have replaced oil pump and sender, have checked the wiring, new gauge, did clearance. Please help, I want to drive my jeep.

  2. What do you mean by "we will have oil pressure and then the next time we drive there will be no pressure".

    My jeep has an issue where once the engine is warm, if I shut off the jeep. Ten minutes later when I turn on the jeep it has no oil pressure. I know it's not a sensor issue since the engine knocks. I replaced the oil pump with a high volume oil pump (mueller I think). That helped a lot. If I had to guess I suspect the crankshaft needs to be ground down and bigger bearings are needed ?

  3. #3
    Join Date
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    Re: 1978 cj5 AMC 304 no oil pressure

    You replaced the pump, sender, gauge. what type of gauge, electronic or mechanical? Electronic was factory and they fail often, I have never trusted them and always switch to a mechanical gauge. I would start by having your husband take off a valve cover and have you start the jeep up while he watches to see if oil is actually being pumped to the rocker arms. put some rags under the jeep or around where the valve cover go's because it will make a mess, shut it off once you see oil is being pumped. if oil is being pumped to the rockers then I would replace the electric gauge with a mechanical. Let us know what you find. if oil is being pumped to the rockers, you can drive it :)

  4. #4
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    Re: 1978 cj5 AMC 304 no oil pressure

    If you have no oil pumping to the rockers, I would say you have a blockage in the oil passages inside the engine. that can be cured SOMETIMES with out taking the engine apart and we can address if need be. see if you have oil pumping first.

  5. #5

    Re: 1978 cj5 AMC 304 no oil pressure

    The 304 has a "splash plate" that sits behind the timing chain & gear. When the plate wears, oil pressure suffers. Not sure if that is your issue,but thought I would mention it as a possiblity. 69jeepcjs' plan of checking for oil at the rocker arms is a good idea,but I'm not sure if a worn "splash plate" would affect oil there or not.
    Tom Landvogt
    1978 CJ5(my toy)
    2001 Cherokee Sport(winter daily driver)
    2002 Dodge Dakota(summer daily driver)
    2017 Ford Escape(wifes' driver)

  6. #6

    Re: 1978 cj5 AMC 304 no oil pressure

    Thank you for all your help.
    Verified no oil pressure. Reprimed pump. Started with 60 psi, slowly worked it's way back to zero again. Let cool down and still at zero. Engine is fresh and no apparent wear problems.
    Thank you for taking the time to help.

  7. #7
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    Re: 1978 cj5 AMC 304 no oil pressure

    is oil getting to the rockers? If no, my brother and I have successfully unclogged two engines with plugged oil galleys by taking off both valve cover and blowing compressed air into the oil holes of the head, and using PB blaster or the like, spraying it into the holes and letting it soak then blowing compressed air again. repeat and repeat. we sent a hour here and a hour there and in a day or two it broke free.

  8. #8
    Join Date
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    Re: 1978 cj5 AMC 304 no oil pressure

    is oil getting to the rockers? If no, my brother and I have successfully unclogged two engines with plugged oil galleys by taking off both valve cover and blowing compressed air into the oil holes of the head, and using PB blaster or the like, spraying it into the holes and letting it soak then blowing compressed air again. repeat and repeat. we spent a hour here and a hour there and in a day or two it broke free.

  9. #9
    Just a thought, have you checked the shaft that goes up to the distributor? Is it completely engaged into the distributor notch?. If it's barely in the notch, it could intermittently slip.

    Sent from my iPad using Jeepz
    Confucious says: Don't eat the snow where the huskies go!

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