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Carb Backfire... Help!

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  • [Corsa B 1993-2000] Carb Backfire... Help!

    Hi guys

    Cars been running fine up until starting it tonight, there's now a squeaking and backfire (throws the petrol out the carb) on cylinder 2. Never done this before and its even popping out the exhaust on idle (Sounds more clear with headphones)

    Here's a video so hope someone can help:
    VID_20131104_222317_zps19696f77.mp4 Video by liquidd_monkeyy | Photobucket

    Left heavy carbon almost oil like deposits in the backbox after a few minutes of running very rough

  • #2
    Start with checking the timing.
    1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

    Comment


    • #3
      Originally posted by Taurus View Post
      Start with checking the timing.
      Will do thanks Taurus, Could the belt have slipped?

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      • #4
        Poorly valves?

        Comment


        • #5
          Originally posted by Sam_Sri View Post
          Will do thanks Taurus, Could the belt have slipped?
          Possibly - anything to do with backfires, especially through the carbs, then it's always worth checking the timing is OK before progressing further.

          Originally posted by P1nky View Post
          Poorly valves?
          That's a possibility of course - hopefully not. If the timing has slipped far enough then it can happen. Or they can just stick or burn out. If the timing is spot on then the next step is to check the compressions. As ever, take it one step at a time.
          1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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          • #6
            Thanks for the advice guys, I'll start with checking the timing tomorrow evening then go from there.

            Hopefully its not head related as I've only just rebuilt it.

            I find it odd that one day the cars fine and next time I start it, its like this, would have expected it to happen whilst driving or something.

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            • #7
              Iirc youre on bike carbs arent you? Ive seen them stick before

              Comment


              • #8
                Originally posted by P1nky View Post
                Iirc youre on bike carbs arent you? Ive seen them stick before
                Sure am mate, yeah? Thanks for the info I'll add that to my list to check.

                Found a total Vauxhall PDF which shows how to fully strip and clean bike carbs as I've only partially stripped and cleaned them before, so am going to try that after checking the above suggestions

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                • #9
                  id put money on it being the belt slipped a tooth or two. normaly happen on first crank. check the belt tentioner hasnt slackened off.
                  Take a look, Its old and rusty[URL="http://www.thecorsa.co.uk/projects-builds/182-zetec-powered-mk1-fiesta.html"]
                  http://www.thecorsa.co.uk/projects-builds/182-zetec-powered-mk1-fiesta.html[/URL]

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                  • #10
                    Timing will be checked tomorrow as i'm missing the socket i need to turn it over by hand and will be doing a compression test at the same time.

                    Last night i re-fitted the carbs, checked the plugs which looked awful, checked ht leads etc and when i started it, it run like normal! apart from a very unhealthy fuel/oil smell. Took it for a drive and it ran strong!

                    BUT.... Started up today and its doing the same as the first video but worse and gets better as the engine warms up (less carb backfire) but still runs lumpy.

                    Plugs...

                    /IMG_20131105_174407_zps3fc0c619.jpg.html]"]Photobucket

                    I think the oil on this one is due to a rocker cover leak but will double check tomorrow.. Just to note this one looks the worst but is cylinder 4 plug but its cylinder 2 carb which is having the issue:

                    /IMG_20131105_174346_zps1ed7db0e.jpg.html]"]Photobucket

                    Video after start up:

                    VID_20131105_190650_zpsa0ee7026.mp4 Video by liquidd_monkeyy | Photobucket

                    After 15mins running:

                    VID_20131105_192006_zpsa84ea064.mp4 Video by liquidd_monkeyy | Photobucket

                    After a drive round the block: (bangs are fireworks)

                    VID_20131105_193106_zpsc0b51ade.mp4 Video by liquidd_monkeyy | Photobucket

                    But obviously back to square 1 now. I've got HT Racing at brands hatch lined up to map the ECU on the dyno but i need this sorted first and the carbs balanced.

                    Any help is appreciated

                    Comment


                    • #11
                      When were the plugs last pulled to check them?
                      Is it just one cylinder that has oily deposits as bad as that?
                      Were the valve stem oil seals and guides done when the head was rebuilt, or was it pressure tested?

                      It looks like it's burning oil in at least one cylinder.

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                      • #12
                        Originally posted by Hardcore View Post
                        When were the plugs last pulled to check them?
                        Is it just one cylinder that has oily deposits as bad as that?
                        Were the valve stem oil seals and guides done when the head was rebuilt, or was it pressure tested?

                        It looks like it's burning oil in at least one cylinder.
                        Probably about 4 weeks ago and they just showed signs of slight over fuelling. And yes just the one cylinder but it's not the one that I'm getting backfire off.

                        Stem seals were replaced but not the guides, head was machined and tested and came back fine

                        Comment


                        • #13
                          When you done the sump gasket was there any smell of petrol from the oil?

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                          • #14
                            Hmm - to be honest I'd check the timing and compressions before doing anything else. You need to know those are good first of all.
                            1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

                            Comment


                            • #15
                              I didn't notice a distinctive smell of petrol tbh seemed all normal when we did it.

                              Sure thing I'll report back tomorrow evening and go from there

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