Oil pump priming question

Small Block Mopar Engine

  1. Dusten

    Dusten Active Member

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    I have a 71 Duster I just dropped the 340 LA engine back into. Went to prime the oil pump/engine with the hex head tool and drill. After 4 to 5 minutes of priming the oil gauge only read about 5 -10 psi. I took the oil gauge off and blew compressed air into it and the gauge moved to about 20-25 psi. Then I primed the engine with the oil gauge of to see if oil was coming out and just a drop every now and then. When I took the copper gauge line out at the block and primed it, tons of oil cam gushing out. So I know lots of oil is getting to the start of the oil gauge line just not going through it. So I bought a new copper gauge oil line. installed it and made sure I didn't kink it. Same thing when I prime the engine I get lots of oil to the start of the copper line but just little drops of oil to the oil gauge and the gauge only reads 5-10 psi. Also have not seen oil get to the rocker arms yet. priming clockwise and turned the engine over slow clockwise. Is there something I am missing? Do I just need to prime it longer? I have primed it for about 6-8 minutes. so much that my drill starts to heat up really hot so I stop to let it cool down. Other have said it take a couple of minutes, so I feel like it should be showing oil pressure at least by now. Thank in advance for any help.
     
  2. Garry in AZ

    Garry in AZ Building a 9 second Valiant FABO Gold Member

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    It shouldn't take more than 15-20 seconds for you to see oil pressure. I'd try a different gauge first, and see what happens. It also sounds like you need to determine what is causing the restriction in the copper tubing. I wouldn't start the motor until I had this figured out.
     
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    • furyus2

      furyus2 Well-Known Member

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      Does the oil come out of the oil pressure line, if you remove the gauge? No? check the next fitting closer to the engine. Keep going until you find the restriction. Or go to the auto parts store, and buy a whole new gauge, and tubing kit. Much cheaper than an engine.
       
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      • Dusten

        Dusten Active Member

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        Thats what I did, there was only small drops coming out of the tubing the goes into the oil gauge, but lots of oil coming form the engine into the oil gauge line. So I thought the oil gauge line was clogged up. So I bought a brand new copper line and the same thing is happening.
         
      • Garrett Ellison

        Garrett Ellison Amateur driver on public roadway, do not imitate..

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        Somethings up, the lack of oil up top to the rockers is probably a sign that the galley plug behind the cam gear is missing.
         
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        • flyfish

          flyfish C8H18+N2O = :-D

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          If I recall correctly, if you put the motor at 90° before TDC on the compression stroke you should get oil to the passenger side rockers. 20° after TCD and you should be getting oil to the driver side....this is what I recall from a post WAY back by 70aarcuda.

          I only primed mine for 10 seconds or less with a drill. You should see pressure in seconds after the oil filter fills.
           
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          • AAndrews

            AAndrews Supercuda

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            So lets start at the beginning. What was done to the engine while it was out of the car? Did you use the same oil gauge setup before to check oil pressure before you removed the engine?
             
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            • gzig5

              gzig5 Well-Known Member

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              Flyfish is onto something. There are certain crank positions that block the oil ports to the heads.
               
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              • 1994redram

                1994redram FABO Gold Member FABO Gold Member

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                Check for the oil plug by the distributor. Check for the oil plugs behind the cam timing gear. The oil will take the path of least resistance, so when the oil gauge port is open/unplugged you said you had oil gushing out. But when you put the copper tube in it, you now have resistance and only got a couple drops. The oil seems to be exiting somewhere else.
                 
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                • brian6pac

                  brian6pac Well-Known Member

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                  Yea I agree he has a plug out somewhere, galley by the dist.
                  Here is my buddy's 495, priming cold w/20w50
                   
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                  • rustycowll69

                    rustycowll69 Well-Known Member

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                    as far as the gauge is concerned you should bleed the air out of the line where it goes into the gauge.
                    There are several oil galley plugs that need to be in place. there's one they mentioned in the rear of the left lifter gallery. You should see it just above and in front of the intermediate shaft gear. I can't remember for sure but there is probably one on the rear of the Rt gallery, too. There's another one below(block inverted) the rear main cap. When this plug is in place it directs the oil from the pump and to the oil filter. If it is left out, you will get only partial oil filtering. I doubt that that is your problem, because it wouldn't have much to do with oil pressure, just filtering (that's important, too). There's another one, I think, in the oil filter boss of the block.
                    Did you use Teflon tape on any of the fittings? You have to be careful with Teflon tape. You have to wrap in the correct direction, and hold it away from the first thread or two. If a Teflon booger hangs out it can block an oil passage.
                    Did you prime the oil pump with oil when you installed it? I pack the oil pump rotors with Vaseline. It stays in place until you're ready to finally prime the engine after it is installed.
                    There is a remote possibility the oil pump relief valve could be stuck partially open.
                     
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                    • Dusten

                      Dusten Active Member

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                      No teflon tape was used. I did prime the old pump when we installed it. I will start checking out all of the oil galley plugs.
                       
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                      • Dusten

                        Dusten Active Member

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                        This sounds like what it could be. I will start checking the oil plugs.
                         
                      • 67Dart273

                        67Dart273 Well-Known Member

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                        Air has nothing to do with the oil gauge. If you actually have pressure, the gauge will read, air in line or not. You sure you are not over-tightening the line fittings so much that the compression is squeezing the line?

                        I'd remove the line/ gauge, and hook them up to an air source, regulator or inline valve if possible, and "see what you have."

                        Most likely plug left out is the "trick" one that is INSIDE the engine down by the distributor bushing. You can see that by pulling the dist. with a flashlight. There's been a couple of members on here actually got them back in through the dist. hole. If not you could pull the intake

                        plug.jpg
                         
                        Last edited: May 25, 2019
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                        • Dusten

                          Dusten Active Member

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                          I will definitely check that one out. How many oil plugs are they on the 340 engine?
                           
                        • Dusten

                          Dusten Active Member

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                          So I checked both of the plugs in front and back of the distributor shaft, both were there. If the plugs were out on the back of the engine would it run down into the bottom front of the transmission bell housing? Nothing leaking there and I looked and felt around inside the bottom of the bell housing and it is dry all along the bottom. Or would the oil drain into another part of the transmission? Was hoping I would have to drop the trany to check the plugs back there.
                           
                        • yellow rose

                          yellow rose Doctor of Thinkology.

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                          Post 14 shows a picture of the plug you may be missing. You can't see it with the gearbox out. You have to pull the distributor out and physically look in there to see if it's there or not.

                          It can be missing and you wouldn't have an external leak.
                           
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                          • Dusten

                            Dusten Active Member

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                            Yes the plug pictured in post 14 is in. I already had the distributor and the intermediate shaft out. I had to take those out to prime the oil pump with the priming tool and drill. I was thinking about other possible oil galley plugs that might be out. I thought there were two on the very back of the engine that are covered up by the transmission. Also I believe some are behind the cam timing gear.
                             
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                            • yellow rose

                              yellow rose Doctor of Thinkology.

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                              There are two plugs on the back of the block. The one covers up the hole that gives you access to the drivers side plug. The other is for the passenger side gallery and if that was missing, you'd know. You'd be knee deep in oil by now.
                               
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                              • Garrett Ellison

                                Garrett Ellison Amateur driver on public roadway, do not imitate..

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                                If it’s not behind the upper cam timing gear, the fault probably lies with with a pickup tube that is pulling air or is partially blocked by debris (I am thinking of cellophane/plastic wrap, had family in once from S.D. drive down on a fresh rebuild and they lost oil pressure at once. I pulled the pan and lo and behold...). It could also be the oil pump to main cap mounting surface is warped or the gasket is missing. This is also assuming that bearing clearances are all within spec and that it’s not a dreaded “diamond stamped” block that requires the .008 oversized lifters with standard sized lifters in place.
                                 
                              • nm9stheham

                                nm9stheham Well-Known Member

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                                There are also plugs at the front of both oil galleries. They are covered by the cam plate. The cam plate helps block that area, but if those plugs are missing, that has been known to leak enough to lower pressure. Timing cover has to come off to inspect.

                                As for the air suction, if the oil pump is not seating square on the rear main bearing cap, then that will cause both suction and output pressure problems.

                                And the pressure relief bypass valve in the oil pump could be jammed open.
                                 
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                                • Locomotion

                                  Locomotion Well-Known Member

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                                  Do you have anyone that can rotate the engine by the balancer bolt while you run the priming drill?

                                  Also, did anyone mention the "cup" plug that's installed in the passage under the main cap, part way towards the top where the oil pressure fitting goes? It bottoms out part way between the two. You might be able to figure out if it's there by dropping a long thin rod down the pressure fitting hole by the distributor. It shouldn't reach the main cap.
                                   
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                                  • Locomotion

                                    Locomotion Well-Known Member

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                                    After re-reading the posts, I see that rustycowll69 did mentioned the cup plug. I don't recall the size, but it's listed in one of the Direct Connection manuals and I believe it slightly different than what goes into the lifter galley passages behind the cam plate.

                                    If dropping a thin rod down the oil pressure passage determines it's missing, you'll have to drop the pan and the rear main cap to put the correct sized plug in. Here is the diagram and old part #. But I haven't been able to find the plug size.
                                     

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                                    • nm9stheham

                                      nm9stheham Well-Known Member

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                                      At the risk of re-igniting an old debate, the particular oil plug last mentioned just forces the oil to flow through the filter. Being left out means the oil bypasses the filter. But it would not drop the pressure to such low levels. The distance from the top of the block to the plug has been measured and mentioned in at least 1 thread here.
                                       
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                                      • Locomotion

                                        Locomotion Well-Known Member

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                                        It could be a combination of issues!

                                        Another possibility is #5 main cap bolt related. Did you use washers under the bolt heads and/or use aftermarket main cap bolts? I've has instances where a washer caused one of the bolt heads to interfere with the oil pump housing, keeping the mating surfaces from sealing. Solution was to grind down the head and/or the oil pump body for clearance.....or just leave off the washer on that one.
                                         
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