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Volvo Penta AQ131D compression problem

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  • Volvo Penta AQ131D compression problem

    I tested the compression on the motor this weekend and found my rough idle culprit. Here's the results.

    Cylinder 1: 3psi
    Cylinder 2: 150psi
    Cylinder 3: 120psi
    Cylinder 4: 150psi

    #1 is a real problem, I'm thinking a broken valve or something
    #3 is probably worn piston rings, valve seating issues or something.

    This is outside my area of expertise and I lack the special tools to perform this work. Does anyone know a reasonable shop in the southwestern Ontario area that could do this type of work? Can I take it to a regular mechanic or does it have to go to a marine shop?

    Any idea what type of price tag I'd be looking at?

    Thanks,
    Trevor.
    Thanks,
    Trevor.

  • #2
    I took the opportunity to remove the intake and exhaust manifolds this weekend to have a look. The exhaust side looks okay. The intake side looks carboned up so I'm thinking it's not sealing. Not sure what to do with this information now but it's interesting. All the valves move when I hand crank the belt drive however I cant move it too much before things tighten up.
    Thanks,
    Trevor.

    Comment


    • #3
      I would check to see if the timing belt jumped a tooth.
      This can cause compression problems and is easy to fix.

      Valves may appear to move, but it is difficult to see if they fully close or seal.
      Dennis
      20' 1987 Renken Cuddy Cabin
      AQ131C 270 drive
      Southern NJ

      Comment


      • #4
        Thanks, a mechanic buddy of mine suggested that because of the carbon and oil deposits in the intake he thinks it's likely a head gasket issue which is probably my best case scenario. He agreed that its difficult to tell if they close properly without pulling the head so I guess I'm playing mechanic for a bit. He gave me pointers on how to position the pulleys so we can get it back together without issues.

        The timing belt slipping a tooth I cant see causing compression issues on only 1 cylinder after considering it.

        thanks!
        Thanks,
        Trevor.

        Comment


        • #5
          One tooth might do what Dennis suggested?

          Why did the belt jump? Old(yes) , pully rusted?
          When it jumps, it usually affects the cam pully.


          Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
          ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

          In Scenic , Beautiful San Sebastian by the sea Florida

          88 Bayliner 21CC 2001 Mercury 225 HP EFI

          Comment


          • #6
            Cam timing would affect each cylinder evenly. Are the valves adjustable on that engine? Is that the little Volvo engine, or a Ford engine? The little Volvo engine was a pushrod engine.

            Comment


            • #7
              Bump the starter around until your on number 1 compression and timing mark lines up on the damper. Now the head can be removed. If all can be freshened up, I would replace the timing belt while your at it

              With all the oil and carbon build up, my guess is the valve just will not seal and may be hung up.

              94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
              95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
              07 Seadoo GTX
              Merc Adults Only VP Adults Only
              G-Dad always said "First Liar doesn't stand a chance"

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              • #8
                Just thought of something, the motor has a over head cam so doesn't matter where the crankshaft is. Just pull the head and prior to reinstall, move number one piston to TDC. Adjust cam on the head to TDC and install the head.
                94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                07 Seadoo GTX
                Merc Adults Only VP Adults Only
                G-Dad always said "First Liar doesn't stand a chance"

                Comment


                • #9
                  Thanks, I'll pay special attention to this on reassembly!

                  It is the little pushrod. it's a 4 cylinder overhead cam and the cam bolts are separate from the head bolts so the head can be removed without removing the cam which is really nice! I just have to remove everything around the head. I have the intake and exhaust off obviously, next is the innercooler, then belt, then head. Sounds easy right?
                  Thanks,
                  Trevor.

                  Comment


                  • #10
                    Originally posted by TrevorStott View Post
                    Thanks, I'll pay special attention to this on reassembly!

                    It is the little pushrod. it's a 4 cylinder overhead cam and the cam bolts are separate from the head bolts so the head can be removed without removing the cam which is really nice! I just have to remove everything around the head. I have the intake and exhaust off obviously, next is the innercooler, then belt, then head. Sounds easy right?
                    Pushrod engine preceded yours. I looked it up..you have a later model OHC engine. Like dodge says, stuff is lined up after assembly. New belt, tensioner, water pump. good to go.

                    If you had defective compression rings there would be massive blowby from the crankcase.

                    Comment


                    • #11
                      Compression ring, Is that on the piston? Admittedly I hadn't thought of replacing the water pump. the tensioner I was planning on inspecting and re-installing. Parts for this thing are harder to find and expensive when you do. I can find some on E-bay but the shipping usually kills me being in Canada.

                      *Edit*
                      Found the compression ring in the manual, it's on the piston. If it's that I'm not sure what I'll do. The reason is that if it's a broken compression ring it's probably damaged the cylinder wall and gets into tearing apart the whole lower section, crankshaft, etc... I'm a woodworker not a mechanic. I'll jump off that bridge if I get to it but I'm seriously hoping it's just the gasket!

                      Thanks,
                      Trevor.
                      Last edited by TrevorStott; December 11th, 2018, 08:06 AM.
                      Thanks,
                      Trevor.

                      Comment


                      • #12
                        Originally posted by TrevorStott View Post
                        Compression ring, Is that on the piston? Admittedly I hadn't thought of replacing the water pump. the tensioner I was planning on inspecting and re-installing. Parts for this thing are harder to find and expensive when you do. I can find some on E-bay but the shipping usually kills me being in Canada.

                        *Edit*
                        Found the compression ring in the manual, it's on the piston. If it's that I'm not sure what I'll do. The reason is that if it's a broken compression ring it's probably damaged the cylinder wall and gets into tearing apart the whole lower section, crankshaft, etc... I'm a woodworker not a mechanic. I'll jump off that bridge if I get to it but I'm seriously hoping it's just the gasket!

                        Thanks,
                        Trevor.
                        The point is..if it was a compression ring issue, there would be so much blowby the engine would probably leaking oil everywhere.

                        Comment


                        • #13
                          2Xs with Aimlow’s opinion. The only thing this points to is an exhaust valve problem. If this was a pushrod style engine I would be thinking about a worn intake cam lobe if the valves were not burned.
                          There are shims under the “buckets” that ride on the cam which sets valve lash. Make sure that the clearances are in spec after the cam is installed back on the head.
                          Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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                          • #14
                            Got the head off the motor. No slop in the pistons, cylinders look amazing. Going to get the head tested tomorrow. Surprisingly the head gasket looked good as well. I'll let you guys know how the head test goes.
                            Thanks,
                            Trevor.

                            Comment


                            • #15
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                              Originally posted by TrevorStott View Post
                              Got the head off the motor. No slop in the pistons, cylinders look amazing. Going to get the head tested tomorrow. Surprisingly the head gasket looked good as well. I'll let you guys know how the head test goes.
                              NEVER! reuse a head gasket. Must be a valve issue.

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