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Thread: #4 cylinder still won't work.

  1. #1
    Senior Member c130jake's Avatar
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    Default #4 cylinder still won't work.

    While I wait for Monday, are there any engine/electronic ignition experts who might want to add to my troubleshooting homework?

    Engine starts and runs a little rough since #4 isn't working. Checked for fuel and spark, checked all the coils, rechecked the plug wires, verified firing order, blocked the primer, switched plugs, rechecked wires from electronic ignition, adjusted magnetic pickup again to .040 and made slight adjustment on top sensor to line up line on ring. (It was off by .030-.050 in the vertical)

    The last two things in the plasma trouble shooting decision tree not yet tried is a compression check and putting a timing light on it. I put an automotive compression test on it today and got 60psi. I don't have access to an aviation one so I don't know if it leaked down past a valve. Not sure how to time the engine and don't have a timing light.

    Between Mitch and the guys in Kamloops, I think I have tried every possible check on the electrical side.

    Other than the engine not working, my build is done minus the front wing to fuselage fairing. (Waiting for the glue to dry)

    Thanks

    Jake Hayes


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  2. #2
    Senior Member Cubrath's Avatar
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    Default Re: #4 cylinder still won't work.

    I feel for you Jake! So close to being done then a major issue.

    If the plug on the number four is wet it is getting fuel. It has compression so my bet would be still be in the ignition. Have you verified spark on the #4 plugs. There is a automotive tool called an inline spark tester. You can buy at a local auto parts store. You put it in line right before the spark plug and you can visually see if it is sparking. It's cheap and would let you know if you even have power going to the plug.

    Keep us posted!


    Mike


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    Last edited by Cubrath; 06-25-2016 at 09:32 PM.

  3. #3
    Senior Member c130jake's Avatar
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    Default #4 cylinder still won't work.

    I checked for spark first, swapped plugs (4 was wet), checked the coils, all were good. Checked firing order by rotating prop and watching spark plugs fire in order. Removed primer line in case of flooding, Checked resistance in wires, coils, leads from the ignition boxes.

    Trying to find a proper compression test unit. It runs the same on left, right or both ignition. I was hoping it would be something easy. Mitch ran out of ideas and had me call Aerosport power. They had me check firing order and the magnetic pickup. Timing and compression check are all that's left. I am surprised at how well it starts and runs on only 3 cylinders. Was hoping to fly it this week. It could be a bad ignition box I guess. I hope it's not a bad cylinder/engine like the other Jake.

    Jake


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    Last edited by c130jake; 06-25-2016 at 09:54 PM.
    Jake
    Finished CCEX N96FV!

  4. #4
    Member DRL's Avatar
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    Default Re: #4 cylinder still won't work.

    It seems like an ignition problem, but if any ignition component has failed, there would also be a problem in another cylinder. Conversely, there is no one common ignition component that would simultaneously affect both spark plugs. Attached is a diagram that we made to better understand how it is wired. It is still possible that this has something to do with the plug wires, but that looks like it would require a double failure. Crimping the RG400, shields and cores, is not easy, nevertheless it should fire off even with a high resistance cable, just not smoothly. One other thing to check; the cables to the ignition boxes and the BNC connectors. Ours were pre-made, but it is possible to get a short if someone did not build it correctly.

    Unless their is some induction blockage, which is highly unlikely, that can be eliminated. So, if you took the valve cover off and saw the values are working, while turning the engine over, it probably is getting fuel to the cylinder. This is a real mystery, we will be very interested with what you discover. Mitch is rarely stumped.

    Dave
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  5. #5
    Senior Member Cubrath's Avatar
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    Default Re: #4 cylinder still won't work.

    I'm just thinking out loud here. You are going to need an aviation compression tester but in the mean time I would think you could hold your thumb over the spark plug hole while you rotate it through and see if you are getting the normal suction and compression cycles. Would it be possible that the intake or exhaust valve is stuck?? You could pull the valve cover off and see if they are moving normally.

  6. #6
    Senior Member c130jake's Avatar
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    Default Re: #4 cylinder still won't work.

    We did that. It was sucking any blowing with a finger on the spark plug hole. The guys on the field think sticking valve. I am hoping is a simple wiring snafu and I haven't found it yet. What are the odds it's a bad cylinder on a new engine?

    I should be flying it today. 🙁

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    Jake
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  7. #7
    Senior Member c130jake's Avatar
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    Default Re: #4 cylinder still won't work.

    I will recheck the RG400 cables. We checked the core for continuity and to make sure LA,LB,RA, and RB were on the correct coil. Before we pull a jug, I will pull the induction pipe. I did the SB but don't remember looking up at the valve. It was pretty cold in the hangar that day if I remember. Thanks for the schematic.

    Jake Hayes

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  8. #8
    Member DRL's Avatar
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    Default Re: #4 cylinder still won't work.

    Quote Originally Posted by c130jake View Post
    What are the odds it's a bad cylinder on a new engine?
    I would say very low, the engine has been run-in, so it worked once. Ours sat on the hangar floor for about 9 months before we started it. There was some concern with that, even though it should have been prepared for long term storage before we received it. I agree, observing the valve movement is probably next, and easy to do.

  9. #9
    Senior Member c130jake's Avatar
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    Default Re: #4 cylinder still won't work.

    Induction leak. I must have jacked up the SB last winter. Got #4 to run by using the primer. I will take it apart and try to stop the leak. Big thanks to Klaus at lightspeeed. He had me check if the induction tube was perfectly centered. It wasn't....after letting me know it couldn't possibly be his electronics.

    Much better than a cylinder or engine swap.

    Jake

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  10. #10
    Senior Member Cubrath's Avatar
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    Default Re: #4 cylinder still won't work.

    Wow! I wouldn't have thought that intake could have been misaligned enough to get the hose on then not to fire. I just did my intake SB this week. The only thing I didn't like is how the edges of the hose turned up slightly when the clamps were tightened up to the required spec. I'm sure it has a good seal! I'm glad I did it, after 50 hours I already had drops of shrink tube glue in the bottom of the cowl and fuel staining.


    Glad you got it figured out Jake. The good news is your ignition system has been triple checked!! Let us now how the inspection goes!

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