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5.0 Volvo Penta GXI rough idle and knocking

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  • #46
    muc I'm having the worst time trying to find specific information pertaining to my specific engine model. One thing I did tonight, I went out and with the key in the on position, I connected to the distributor wiring plug and am getting 5V there. Seems strange.

    I also disconnected the high tension line from the coil and cranked the engine running that line to ground and am getting spark but it is WEAK. Obviously weak enough that I'm not able to visibly see spark coming from the distributor via plugs.

    All the manuals talk about the purple wire from the coil and testing for 12V there. I don't have a purple wire at all. I'm thinking about swapping out the coil anyways but really would like to troubleshoot it first if possible. I ordered this: https://vod.ebay.com/vod/FetchOrderD...&ul_noapp=true. Hoping it'll help


    • #47
      If you click on the above link, it will take you to where you can get the correct manuals. Put your serial number in and click search. All the manuals for your specific engine will show up.
      Not sure what manuals your looking at that talks about a purple wire to the distributor. But they aren't the right ones.
      The computer controls the ignition on your engine. Without a scantool there is very little that you can test. The ignition system is one thing that you can test, but i fear that you will cause more problems if you do it wrong. That's why I suggested the service bulletin.

      Parts swapping is usually a a bad method for troubleshooting, especially if the parts your using come from anybody other then Volvo. Swapping out with aftermarket parts has a better chance of making things worse.

      Have no idea what you ordered from eBay. That link only works for the person who placed the order.
      Good Luck Muc


      • #48
        muc solid reminder on OEM Volvo products. I have a genuine Volvo EFI diagnostic manual coming from ebay (that was the link). I replaced The ignition coil/module/heat sink with new Volvo product. No change.

        I’m done part swapping now So I checked the voltage with key on at the CKP and it’s 4V. Seems to me that it is supposed to have B+ (12V min), right?

        Same is true for the CMP wiring plug at the distributor.

        The starter solenoid intermittently seizes and gives that lovely click almost as if the battery is undercharged. Battery is fully charged. Wondering about the starter relay. Would that have the ability to cause low/no voltage to the ignition system?


        • #49
          Those are 5 volt sensors. Anything below 4.9v is bad and must be corrected. Could be battery, wiring or one of the other 5v sensors causing it.
          Good Luck Muc


          • #50

            I was finally able to get it into a certified VP shop. I found a couple other posts on here with MAP sensor issues. Well as it turns out. The MAP needed to be replaced as well as the (what I'm calling the CAM sensor) beneath the distributor. Both of those sensors replaced (along with my tuneup and starter motor replacement) and the boat is running like a top!

            Had her out on the Mississippi the other weekend and heading back out tomorrow.

            So as a rundown:

            I was slowly moving in gear when it first stalled. Could NOT get it restarted. Opened the engine compartment and the bilge was full of water. Turned the bilge pump on and pumped it out while getting towed in. The bilge housing was broken likely from being winterized full of water.

            Got it trailered and took it home to dry it out and replaced the bilge pump. Did a full tuneup, plugs, wires, rotor, cap. Able to get it to start but did NOT sound great. Intermittent stalling at idle, intermittent no start, stalling when putting it in and out of gear.

            Replaced starter motor assembly as it tested bad and was starting to fail. Replaced ignition coil assembly which I still have as that did not resolve the issue. Wasn't getting spark still.

            The FIX was the MAP and CPS sensor as both had failed but they weren't throwing codes.

            At any rate, I hope this resolution helps anyone else out. I'm happy to salvage the rest of my boating season.



            • #51
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              Thanks for the update. Glad they got you back on the water. Two sensors failing at the same time is rare. But when it does happen it can be difficult to troubleshoot.
              Good Luck Muc