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470 poor starting after rebuild

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  • 470 poor starting after rebuild

    Well I finally got her started today and she runds nicely.

    She did take a long time to get started but once running the engine is like a sewing machine so I am pleased.

    Residual issue is that she is hard to start even once warm. I set the ignition timing using a strobe to 5 degrees btdc. I did this using the strobe pointed at the middle TDC notch and turned the distributor so that it read 05.xx with the timing mark aligned to the centre mark on the engine casing.

    She is fitted with pertronix ignotion so no condenser or points.
    Battery is good and showing 13 volts.
    Fuel is fresh.

    I have primed with 3 full strokes of the accelerator then crank. sometimes she will fire up but nore often she wont.

    Am I flooding the chambers or is there not enough fuel coming through ? If I pump the accelerator I see a solid squirt of fuel from the carb looking down in to the flame arrestor.

    Choke is working fine but fully open by the time I shut off and wat to restart.

    I have removed the resistance wire and run in a new regualr wire between the coil and choke. 12 V present at the coil.

    Any Ideas ? My gut feeling is either too much fuel or too little.

    I'd like this engine starting reliably and every time before taking her on a test ride.

    Vid - https://youtu.be/E6xzFMlSRlY

    Any help gratefuly received.

  • #2
    When you look down the throat of the carburetor and work the throttle does fuel discharge from the accelerator nozzles?
    If not that could be the problem.
    Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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    • #3
      Hi Kenny - yes there are 2 jets of fuel when actuating the throttle linkage by hand

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      • #4
        Is there a way of finding out if it’s flooding or getting too little fuel to eliminate those possibilities?

        i guess fuelling can’t be too far out as when she does run she finds well.

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        • #5
          what happens when it's warm from previous good run, and you try to start with no throttle?

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          • #6
            Same thing - no start.

            timing wise I have a gunson strobe with timing readout on a small screen.

            when setting the timing I am using the centre notch on the engine casing which denotes TDC to time to.

            I fire the gun at the balancer and adjust the distributor
            little by little until the balancer white line aligns with the TDC notch on the casing when the dial on the gun is rotated until the gun says 4 degrees when the tdc mark and balancer line match up.

            im now questioning if I’m doing this correctly ?

            this is the link to the light
            http://www.gunson.co.uk/product/G4123

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            • #7
              From the manual -

              the advance control knob (D) fully anticlockwise. Press the trigger; the light will flash and the display will show 00.00. Direct the timing light at the timing marks on the engine. Rotate the advance control knob slowly clockwise until a rotating timing mark lines up with the fixed mark or tag. If the marks that are lining up represent TDC, then the ignition timing of the engine is the number of degrees shown on the display. For example, if (when the marks line up), the display reads 08.00, then the timing is 8o BTDC. If the timing marks do not represent TDC, but some other timing angle, then add this to the display angle. For example, if the timing marks represent 8o BTDC and the display is showing 00.00, then the ignition advance is 8o BTDC

              looks like I’m am timing correctly so maybe back to fuel

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              • #8
                Connect a volt meter to the + or BAT side of the coil and read the voltage when the starter is engaged. There should be at least 11-12 volts then should drop to 7-8 volts when the engine is running. The “bypass” circuit from the start relay could be the problem.
                Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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                • #9
                  Thanks Kenny I’ll check next time at the yard.

                  what is the bypass circuit and how would it cause a poor start issue ?

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                  • #10
                    I have primed with 3 full strokes of the accelerator then crank. sometimes she will fire up but nore often she wont.
                    Ayuh,..... After ya do the 3 stroke prime,..... Where do ya set the throttle before ya turn the key,..??

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                    • #11
                      Bondo - tried full off, a little open and fully open.

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                      • #12
                        The “bypass circuit” provides current when the key is turned to “start” because only the start side of the ignition switch has current. Think about your car how every thing, radio, wipers,etc. goes off when the key is turned to start.
                        Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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                        • #13
                          Flooding chambers ...probably not. When it finally does start do you get black smoke? If so may be flooded.

                          I think more likely you have weak or mistimed ignition. If you get a good stream of fuel when pumping the throttle and you have a good spark it will fire right up.

                          would try a spark tester see if you get a good hot blue spark that jumps a decent gap. If orange or weak fix the ignition. If you do have a good hit spark , try rotating the distributor while someone turns the key. Thought being if you are ATDC vs BTDC.

                          Every hard to start engine ive had has been related to weak spark. Fixed the ignition just look at the key and it starts ...

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                          • #14
                            Thanks for the advice Scott, you might be on to something, when I last checked the spark I wasn’t too impressed, it was small and possibly orange. I’ll have to go back and re check but it’s hard being at the helm and seeing the spark at the aft. I’ll hwve to find and assistant and re check

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                            • #15
                              Sign up today
                              Originally posted by kenny nunez View Post
                              The “bypass circuit” provides current when the key is turned to “start” because only the start side of the ignition switch has current. Think about your car how every thing, radio, wipers,etc. goes off when the key is turned to start.
                              Merc ignition switches leave power on the 'RUN' post when turned to 'START'. So he's not losing spark because of the switch being turned to start.

                              Rake722 What sort of compressions do you have? Have you verified that the TDC position you're using is actually TDC?

                              Chris.......
                              xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                              The world takes on a whole new perspective when viewed from 100’ below.
                              1972 Bertram ‘Bahia Mar’ 20
                              2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                              (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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