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help please.. Cylinder 2 & 4 cold (not firing)

Discussion in 'XJ Technical Chat' started by amiel1157, Apr 1, 2016.

  1. amiel1157

    amiel1157 Member

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    hi.. have been trying to back read old post trying to find solution to my problem can't find something that exactly the same as mine..

    my bike run ok for many months now been using her :) almost daily .. yesterday I loaded up on the usual regular 91 octane gas here (the cheapest one) then went to manila via NLEX super high way (100+ kilometers) then encounter super heavy traffic on my way home she never died on me but on the very hot day with the oozing mud like traffic she started to "sputter" first 10 minutes only a few hiccup from the carbs like BACK FIRING when I was almost home the hiccup from the carbs was so bad as in it felt like there was "POPPING" sound coming from the airbox sounding like small firecrackers..

    after shutting the engine OFF I notice the inline FUEL filter (small plastic see through) was empty.. which is weird because I have plenty of gasoline in the tank.. I think its not the fuel filter cap (I clean it already) causing partial vacuum...

    im NOT sure but I think the emptying of the inline fuel filter is somehow related to my popping carbs.. Please help..

    Also this morning I started her and noticed No# 2 cylinder and No. #4 is not firing as in stone cold, I notice immediately and after maybe 1 kilometer running sluggish she woke up again as if awaken from deep sleep and now back to fighting power...(ALL 4 pots are hot.. this had happen 3x already.. all occasion when the engine was stone cold in the morning..

    Sparkplugs all brand new.. new oil.. no oil leaks whatsoever carbs are clean..

    at first I thought it was the carburators but it runs fine very good idling good top end power 170kph + as long as I don't encounter super hot days with heavy traffic..

    I am lost right now.. I suspect a bad ignition coil (hope not) I do not want to start buying parts that im not sure off..

    what other things should I check? is it fueling problem? ignition problem? thus an old spark plug cap give this kind off problem?
     
  2. amiel1157

    amiel1157 Member

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    also.. lately I have been using the cheapest gas I can find believing the high octane stuff is not that important to my engine.. can this be the cause of the popping carbs when hot? should I empty the tank and go back to high octane juice?

    can my problem be tappet related? won't that show up immediately if it was the valve clearance issue? on idling I here normal engine sound no ticking or clunking...

    also my engine is stock as in 100% stock original air box.. original spark plugs etc.. even the muffler which I have been iching to replace with 4 into 4 setup.. now im not sure.
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    yes you should adjust /check valve clearances first
    valves should make a clicking sound if properly adjusted, follow this link
    AIRHEAD VALVE ADJUSTMENT with Pics

    over heating can cause vapor lock in the fuel line
     
  4. amiel1157

    amiel1157 Member

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    adjusted the valve already around 500kilometers ago..
     
  5. jayrodoh

    jayrodoh YimYam Premium Member

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    There are 2 coils, one fires cylinders 1 and 4, the other fires 2 and 3 so I wouldnt suspect a coil issue, especially if it runs well when warmed up.

    Two pipes being cold when warming up would point to the starter circuit being plugged up. If you have a Morgan Colortune you can visually see if the cylinder is firing. If not firing on initial start, let it warm up and see if the cylinder starts firing. If so, then your starter circuit needs attention. If not but starts firing when you give it some throttle, then you have a pilot circuit or mixture adjustment issue. Have carbs ever been to church?

    Unless your fuel filter is straight up and down and air can escape, it will never be full. Look at it while it's running, you'll see some fuel in the bottom but it won't be full. If totally dry I would suspect something amiss with the fuel cap or the petcock itself. If you have the issue again, you can briefly switch to prime to see if the problem goes away.
     
    Last edited: Apr 2, 2016
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  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Check the condition of your vacuum line. When it sputters, pull over and open the gas cap. What happens?
     
  7. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    So which is it... New plugs, or original plugs? I'd say try a new a set of plugs.....

    I would doubt a coil first..... You said cyls 2 & 4. That would mean both coils would have to be bad. If it were 1-4, or 2-3, I'd be more inclined to say a coil.

    It sounds like you have floats sticking shut, or you may have floats sticking OPEN, your crank case is full of gas and you're drowning. Open the oil filler cap and take a sniff. That will tell us a lot real quick. Dave
     
    Last edited: Apr 3, 2016
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  8. quebecois59

    quebecois59 Well-Known Member

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    If your fuel filter is partially empty, you have air in the fuel line, it's not surprising your engine is popping and not firing properly. I had similar symptoms with my xj900, for some reasons i always have an air bubble in my line. It didn't affect the idle at first, but when I hit the road, the air bubble was sucked in the carbs and then the engine ran rough with lots of popping when accelerating.

    THat's why I'd say you have a feul delivery issue. Try to change your fuel filter, it's cheap.
     
  9. amiel1157

    amiel1157 Member

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    i think found the problem (i hope so :) after checking the gas cap again, found lots of paint chips.. also after check the new spark plugs i just put in VERY black and lots of powder (carbon)
     
  10. amiel1157

    amiel1157 Member

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    thank you
    ! i will definitely change my fuel filter...
     
  11. amiel1157

    amiel1157 Member

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    i will have to verify if i have a sticking "closed" floats.. NO gas in engine oil :)
     

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