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Thread: Distributor oil pump engagement issue

  1. #1
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    Distributor oil pump engagement issue

    Good afternoon
    I have a 1955 CJ5 f134 and having a problem with the engagement of the distributor to the oil pump. I have checked the dimensions from the face of the block at the distributor to oil pump and can't find any reason why It wont fully engage to the oil pump the arm on the distributor is around .100 to .125 from going up tight to engine block can't seem to find out why. The distributor drive drops into the oil pump. Any help would be greatly appreciated.
    Thanks Mike

  2. #2
    Super Moderator bmorgil's Avatar
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    Mike, the distributor will only go in one way in one spot. The drive where it engages the oil pump is offset. If you look closely at it it is closer on one side than the other. It will only go into the oil pump one way. It cannot be indexed. It is a little tricky, everything has to be just right.

    If you just cant get it, this will work. Pull the oil pump. Put the distributor in where you want it with the rotor pointing to number one and the timing mark on 5 deg before TDC. If it wont go down now something else is wrong. Be sure the number one cylinder is approaching firing (compression stroke valves closed). Now carefully reinsert the oil pump bumping the gear until it lines up with the distributor drive.
    Last edited by bmorgil; 10-17-2020 at 05:59 PM.

  3. #3
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    I appreciate the input but very familiar with the procedure, went through all the steps and i rotate the distributor it will drop right in the oil pump drive slot but i still wont go down to the adjusting arm of the distributor flush with the block. i am posting the dimensions of the distributor and the block down to the oil pump.
    1- face of block to oil pump shaft. 7.900
    2- face of block to bottom of the oil pump drive slot 8.189 which gives you .289 depth of slot
    3- bottom of the distributor adjusting arm to end of shaft 8.067
    4- bottom of distributor adjusting arm to beginning of drive tang. 7.809 which gives you .258 length of tang
    5- so with these dimensions i should have .122 clearance when the distributor is installed in block and engaged with oil pump
    all this being said it makes no sense why it wont go down to the block. If any one has an distributor and block that can verify this info i sure would very grateful.
    Thanks Mike

  4. #4
    Super Moderator bmorgil's Avatar
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    Mike, I would pull the oil pump and see if the distributor will drop all the way. At least that will tell you where the issue is.You certainly have checked it out! You are close enough to what I have. I have .255" of shaft engagement and about .125" of clearance. I like the way you are approaching this. It has to be something fairly simple, there isn't much there. I am assuming this is the distributor that came out. If it is a newer replacement from the aftermarket, you are definitely on the right path checking the dimensions. All that said, the distributors on these are a tight fit and often freeze in the block. Did it come out easy? I would say at this point I would pull the oil pump and try to drop the distributor in. It sounds like the bottom of the bore is tight. It could be rust or just some scoring. This would not be unusual. The oil pump engagement slot in the pump gear itself is often filled with crud, also not unusual. It might be as easy as that. Keep me posted, it should go down all the way with what you have measured.

    I would definitely pull the pump and check the receiving socket for the pump shaft in the gear and the fit of the distributor housing into the block with no pump, and the fit of the drive shaft into the pump. I have seen broken shaft ends stuck in the pump more than once. If the shaft breaks it is usually just below the drive gear in the pump. It will drop down and take up your .250" depth leaving only a small amount left to engage the shaft. This occurs when the distributor shaft seizes in the housing and the engine rotates shearing the shaft off at the gear in the pump. I can't think of anything else it could be.
    Last edited by bmorgil; 10-18-2020 at 06:55 AM.

  5. #5
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    Thanks
    I did pull the pump which was the first thing i did, drops right in. as for the distributor i tore down the engine for complete overhaul distributor slid right out, I disassembled oil pump and checked all dimensions per manual and replace all the gaskets. all original equipment only 9000 miles total. With the oil pump removed the distributor drops right in as it suppose to. Surely Baffling........... I am going to try to get a total measurement from distributor block boss to oil pump block boss and check against previous measurements ?????

  6. #6
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    Just came in from the shop pulled distributor and oil pump, measured across from distributor boss in block and oil pump boss. 12.250
    I also measured the distributor engaged in oil pump on the bench 12.312 so there is my problem. the distributor is .060 + longer than the distance between the oil pump and distributor bosses. Anyone have a distributor that could be measured????? i have a extra block and oil pump they both measure the same.jeep distributor.jpgjeep distributor.jpg I am posting a photo of the distributor installed.

  7. #7
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    Ok got it figured out i have two oil pumps and the engagement of the distributor in one is 7.6875 and the other is 7.500 which gives me a difference of .1875 thes dimensions are from the bottom of distributor arm and oil pump where they engage. I will have to see if the one pump is re-buildable.
    Thanks Guys

  8. #8
    Super Moderator bmorgil's Avatar
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    That is truly bizarre. It is the same oil pump from 1946 to 1977. With that being the original Distributor something really weird there.

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