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Thread: O-200 Won't Start, Cough, or anything...

  1. #1
    CarlOrton's Avatar
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    O-200 Won't Start, Cough, or anything...

    Very frustrated.

    I rebuilt my own O-200. I have significant engine building experience from a prior professional life as a Chrysler tech. I also built my own AeroVee VW conversion for my prior plane, a Sonex. I know, I know, it's not the same. One mag was less than 75 hrs when the core became available. I sent the other mag to our local mag shop for 500 hr servicing. The MA-3SPA carb also had less than 75 hrs on it, so I did not send it out for overhaul. I could put 100LL into the fuel bowl, pump the accelerator, and have fuel come out of the accelerator port (on the bench).

    I've been trying to start it. I can crank and crank, and nothing happens anywhere by anything indicating an attempt to start.

    I thought I had spark issues. I re-checked; I'm not 180 deg out, and all timing marks line up. I disconnected the P leads, since I didn't know if the GRT tach sense connection was somehow grounding the mags. I've had folks tell me to hold the spark lead next to engine ground and have the impulse coupler pop to produce a spark. Could not see a thing. Had other folks tell me that was a waste cuz you usually cannot see the spark anyway.... I traced all plug leads to make sure they ran to the correct plugs in the correct firing order. Rechecked using the mag synch tool. Spot on together.

    I then shot some starting ether in the air filter. That produced some pops and sighs. Didn't spray much, so I wasn't expecting it to start. However, I'm *assuming* that because things were popping that *something* was lighting the fuel/air mixture, ergo, the mags must be firing.

    So now I'm thinking fuel issues. Zenith tech support suggesting using a fuel pump to ensure the bowl was filling. Since my wings aren't on, and the tanks are in the wings, I plumbed up a facet pump in rubber fuel line and used a milk jug for a fuel tank. Fuel was getting to the fuel bowl because I had a slight fuel leak at the fuel linlet. Tightened that and tried again, still no sign of life. I checked all the intake manifold rubber joints.

    I can understand if it started and ran poorly or only on 2 cylinders, but not having ANY sign of ANYTHING going on, I just don't know what to do.

    How 'bout filling the fuel bowl with super whiz-bang carb cleaner, let it soak, then drain the bowl and retry with 100LL? Or would that ruin seals and gaskets in the carb?

    I really don't want to replace the carb unless I know for a fact that it *IS* the carb. ~$1000 to "just check" is something I care not to waste.

    Thanks for any suggestions. I'm at a loss.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  2. #2
    Mike Switzer's Avatar
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    I usually use my timing light to verify spark. A trick I have used in the past (on auto engines, before I had a timing light) is get a propane torch, open the valve wide (don't light it) & have someone hold it in the carb mouth while someone else cranks the engine. If you have spark it will try to start.

  3. #3
    cub builder's Avatar
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    Let's take a methodical approach to this. You have to have compression, fuel, spark, and the spark has to be at about the right time. One of these 4 items isn't right. So let's do a quick walk through each of these requirements to diagnose your problem.

    1. Do you have compression when you pull the engine through?
    a. no - fix it.
    b. yes - go to step 2.

    2. Does it spark? Pull all the top spark plugs to ensure that there is no compression available, and the engine can't possibly start. Connect the leads to each spark plug and lay them on top of the cylinder head. Turn the magnetos on and pull the engine through in the hangar with the doors closed and lights off. Does the impulse coupler snap? (if not, fix your magnetos) If you are in a relatively dark hangar, you are going to see the arc on a spark plug if it sparks when the impulse snaps.
    Is there a spark?
    a. No - Possible causes. Bad magneto, incorrect mag switch wiring. (Note: when the switch is in the on position, it opens the P-lead connected to it. In the off position, the switch is actually closed to ground the P-lead.)
    b. Yes - Continue to step 3.

    3. Is the timing correct? With the spark plugs still out and you have turned the engine to where you just get a spark on a spark plug as the impulse snaps, turn the magneto switch off, and back the propeller up 1/4 turn. Put your thumb over the spark plug hole and pull the engine back forward 1/4 turn. There should be compression there. If not, your timing is off, likely 180 if you have checked it with a timing tweeter.
    Is the spark timing correct?
    a. No - correct he magneto timing, possibly removing and re-installing the magneto.
    b. Yes - Continue to step 4.

    4. Are you getting fuel into the engine? You said the accelerator pump on the carb is working. Slowly open and close the throttle plate through it's full stroke several times. If the accelerator pump is spraying fuel, you will have fuel dripping out the bottom of the carb. If you don't have any fuel running out, your accelerator pump is not pumping fuel. There are two reasons why that may happen. Either your accelerator pump is not working, or more likely, you aren't getting fuel to the carb. Let's check to see if the carb is getting fuel. At the back of the MS carb, there is a pipe plug. It could be an allen socket, but is more likely a square or hex shaped pipe plug that is safety wired into place. Cut the safety wire and remove the plug. If there is fuel in the carb, you will have about a cup of fuel drain out through the plug hole when you remove the plug. If not, then you aren't getting any fuel to the carb. Check your fuel system, check the inlet filter on the carb, and check to ensure the float/needle is correct and opening.

    Assuming your engine is assembled correctly, you are going to find your issue if you spend about 30 minutes and go through these steps. Your problem will be found somewhere along the way.

    -Cub Builder

  4. #4
    CarlOrton's Avatar
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    Quote Originally Posted by Mike Switzer View Post
    I usually use my timing light to verify spark. A trick I have used in the past (on auto engines, before I had a timing light) is get a propane torch, open the valve wide (don't light it) & have someone hold it in the carb mouth while someone else cranks the engine. If you have spark it will try to start.
    Interesting thought on using a timing light on a non-running engine. Will the impulse coupling provide enough pop to light the timing light? Also, really like the propane idea, but I've used starting fluid/ether, and as I noted, that will generate some pops/burps/sighs.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  5. #5
    CarlOrton's Avatar
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    cub builder: Thanks for the input! I like your method. My comments interspersed below in caps; not yelling, just to differentiate:

    Quote Originally Posted by cub builder View Post
    Let's take a methodical approach to this. You have to have compression, fuel, spark, and the spark has to be at about the right time. One of these 4 items isn't right. So let's do a quick walk through each of these requirements to diagnose your problem.

    1. Do you have compression when you pull the engine through?
    a. no - fix it.
    b. yes - go to step 2.

    YES - I CAN FEEL IT WITH MY THUMB OVER THE PLUG HOLE. COMPRESSION STROKE ALIGNS WITH THE TIMING MARKS ON THE PROP FLANGE

    2. Does it spark? Pull all the top spark plugs to ensure that there is no compression available, and the engine can't possibly start. Connect the leads to each spark plug and lay them on top of the cylinder head. Turn the magnetos on and pull the engine through in the hangar with the doors closed and lights off. Does the impulse coupler snap? (if not, fix your magnetos) If you are in a relatively dark hangar, you are going to see the arc on a spark plug if it sparks when the impulse snaps.
    Is there a spark?
    a. No - Possible causes. Bad magneto, incorrect mag switch wiring. (Note: when the switch is in the on position, it opens the P-lead connected to it. In the off position, the switch is actually closed to ground the P-lead.)
    b. Yes - Continue to step 3.

    COULD NOT SEE THE SPARK IN DAYLIGHT; THE GARAGE IS TIGHT AND THE WEATHER HAS BEEN COLD; GETTING WARMER NOW. CAN'T ROTATE PROP WITH DOOR DOWN, SO WILL RETRY IN THE NEXT EVENING OR TWO JUST TO SEE IF i CAN SEE SPARKS.

    I DO NOT HAVE P LEADS CONNECTED AS NOTED IN MY POST SINCE I WANTED TO ELIMINATE WIRING/SWITCH ISSUES. IMPULSE COUPLERS (2) SNAP.

    3. Is the timing correct? With the spark plugs still out and you have turned the engine to where you just get a spark on a spark plug as the impulse snaps, turn the magneto switch off, and back the propeller up 1/4 turn. Put your thumb over the spark plug hole and pull the engine back forward 1/4 turn. There should be compression there. If not, your timing is off, likely 180 if you have checked it with a timing tweeter.
    Is the spark timing correct?
    a. No - correct he magneto timing, possibly removing and re-installing the magneto.
    b. Yes - Continue to step 4.

    NOW I'M CURIOUS. I PREVIOUSLY (COUPLA DAYS AGO) PULLED THE PLUGS, ENSURED I HAD TDC COMPRESSION, AND IT MATCHED THE PROP FLANGE TIMING MARKS. IMPULSE COUPLER SNAPS AT THIS POINT. WHEN I INSTALLED THE MAGS, I MADE SURE I INSERTED THE TIMING PIN IN THE LEFT HOLE IN THE MAG (MAGS SAY LEFT ROTATION ON THEIR ID PLATE), AND INSERTED THE MAG, THEN CHECKED WITH THE TIMING TWEETER. YES THE MAGS WERE INSTALLED WITH THE CAM/CRANK TIMING MARKS ON TDC.

    SINCE THE ENGINE POPS WITH STARTING FLUID BUT DOESN'T SOUND LIKE ITS TRYING TO START, AND THE PLUG HARNESS ONLY INSTALLS IN ONE ORIENTATION, IS THERE SOMETHING ELSE THAT MIGHT HAVE RESULTED IN MAGS BEING 90 OR 180 OFF?

    4. Are you getting fuel into the engine? You said the accelerator pump on the carb is working. Slowly open and close the throttle plate through it's full stroke several times. If the accelerator pump is spraying fuel, you will have fuel dripping out the bottom of the carb. If you don't have any fuel running out, your accelerator pump is not pumping fuel. There are two reasons why that may happen. Either your accelerator pump is not working, or more likely, you aren't getting fuel to the carb. Let's check to see if the carb is getting fuel. At the back of the MS carb, there is a pipe plug. It could be an allen socket, but is more likely a square or hex shaped pipe plug that is safety wired into place. Cut the safety wire and remove the plug. If there is fuel in the carb, you will have about a cup of fuel drain out through the plug hole when you remove the plug. If not, then you aren't getting any fuel to the carb. Check your fuel system, check the inlet filter on the carb, and check to ensure the float/needle is correct and opening.

    Assuming your engine is assembled correctly, you are going to find your issue if you spend about 30 minutes and go through these steps. Your problem will be found somewhere along the way.

    I DRAINED THE FUEL BOWL YESTERDAY JUST TO MAKE SURE IT HAD FUEL IN IT. UNFORTUNATELY I DIDN'T COLLECT THE FUEL. THE CARB HEAT BOX / AIR FILTER IS ON THE BOTTOM OF THE CARB SO I DIDN'T SEE FUEL DRIPPING ON THE FLOOR. I'LL REMOVE THE SCAT TUBE AND SEE IF ANYTHING IS IN THERE.

    -Cub Builder
    Just wondering: could the starter not be spinning the engine quickly enough? Didn't think too much about this because the impulse couplings should allow slower speeds like hand propping. Starter doesn't turn too slow, but it's not not at 200 rpm. 60 rpm? just guessing on that count.

    Thanks for the suggestions;

    UPDATE: our son was visiting tinight and, when he left, I decided to pull the prop thru in search of a spark. #1 cylinder did not spark when timing marks aligned and impulse coupling popped. BUT #4 DID generate a pretty good spark. Strong spark.

    I thought the wire harness could only be installed in one orientation. Could I be 90 degrees off? Firing order is 1-3-2-4 so 4 is 90 off from 1.
    Last edited by CarlOrton; 02-28-2022 at 10:29 PM.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  6. #6
    CarlOrton's Avatar
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    Since it was late last night when I tested the spark, I wanted to really make sure I was thorough this AM. I removed #1 plug and put my thumb over the hole and turned the prop until I had compression. The timing marks on the prop flange were correct. No spark on #1 when turning the prop and having the impulse coupler snap. Turns out #2 cylinder plugs both fire when pulled through.

    So. I'm 180 out on something. I say this because the firing order is 1-3-2-4, so #2 would be halfway (180) thru the full firing order. I have not yet tried to see if the plug wire harness cap is in the wrong spot, but everything says it only goes on one way. Both mags state they're LEFT rotation, and I'll swear on a dinner that I put the timing pin in the left hole. I also know for a fact, with photo documentation, that the cam & crank gears are aligned to their respective timing marks.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  7. #7

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    I have an O-200 on my VariEze that I put new mags and a carb on. The thing I almost missed was lining the 24deg BTC mark to the BOTTOM split line of the case.

  8. #8

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    Carl....Random thought here..could the mag output order numbering be an event order rather than firing order? The Eismann mags for the O-435 are that way and it catches people at times...

  9. #9
    CarlOrton's Avatar
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    Quote Originally Posted by CraigCantwell View Post
    Carl....Random thought here..could the mag output order numbering be an event order rather than firing order? The Eismann mags for the O-435 are that way and it catches people at times...
    Craig, these are straight forward Slick 43xx mags. Speaking with the mag shop (Aircraft Ignition Services in Honey Grove) the opinion is that I screwed up installing them. I’ll pull and retime them.

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  10. #10
    cub builder's Avatar
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    Quote Originally Posted by CarlOrton View Post
    cub builder: Thanks for the input! I like your method. My comments interspersed below in caps; not yelling, just to differentiate:



    Just wondering: could the starter not be spinning the engine quickly enough? Didn't think too much about this because the impulse couplings should allow slower speeds like hand propping. Starter doesn't turn too slow, but it's not not at 200 rpm. 60 rpm? just guessing on that count.

    Thanks for the suggestions;

    UPDATE: our son was visiting tinight and, when he left, I decided to pull the prop thru in search of a spark. #1 cylinder did not spark when timing marks aligned and impulse coupling popped. BUT #4 DID generate a pretty good spark. Strong spark.

    I thought the wire harness could only be installed in one orientation. Could I be 90 degrees off? Firing order is 1-3-2-4 so 4 is 90 off from 1.
    OK. Your symptoms and your description are telling me you have the magnetos 180 off. You installed your magnetos with #1 cyl at TDC at the end of the exhaust stroke rather than at TDC on the compression stroke. Pull your magnetos off, Turn the engine until you get thumb compression on #1 cyl and stop at 20 Before TDC and reinstall your magnetos with the installation pin locked in on firing position for #1 cyl in the magneto. Finish your timing with a timing tweeter and you should be good to go. Remember on the Continental, #1 is the back most cylinder on the engine.

    This is a common mistake and something I have seen over and over, even by experienced mechanics that know better. They always tell me it was installed and timed correctly, and it is, but the cylinder only fires every 720, so it's firing on the incorrect rotation of the engine. So, what happens if you will sometimes get a pop when it lights off the fuel, but there's no way it can start or run.

    Starter speed is unrelated as the impulse coupler will provide a hot spark no matter how slowly the engine turns.

    Rereading your reply, you have it firing 90 off. If it was me, I would make sure the mags are timed to #1 cyl at TDC on the compression stroke, then simply follow your plug wires and put them on in firing order. It's an easy fix you should be able to do in pretty short order.

    Good luck with it.

    -Cub Builder
    Last edited by cub builder; 03-03-2022 at 06:50 AM.

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