Onan B48M-GA018 & MS DD13 Work
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  1. #1
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    Onan B48M-GA018 & MS DD13 Work

    Too many issues this spring...the latest of which caused me to remove all the shielding, starter, coil, intake and rebuild my Marvel Schebler DD13, install new Champion RH18Y and clean the cooling fins.

    All appears sound except when I attempted to start the B48M to test everything late this afternoon. Fuel is coming out of the carb. It appears to be leaking through the front gasket area between the two halves of the DD13. My reading on this issue suggests those who experience "fuel shooting out of the top of the carb" have used the wrong gasket (that is, the gasket with the slot). I used the gasket with the two small holes. However, is it possible I installed it upside down?

    I read this thread several times while working through the DD13 rebuild:

    http://casecoltingersoll.com/showthr...0129-Onan-B43M

    I am not going to open the DD13 up this evening. I chose to re-direct my evening toward enjoying Father's Day. I may open the DD13 up before or, after going to work tomorrow but, I must have this 446 running by tomorrow night.

    Let me know what questions you have.

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    rav
    YES, it is very likely that you installed
    the gasket between the halves upside down.

    the gasket has a rectangular hole on the right front of the carb.

    thank you. boomer

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    jfk (06-19-2017)

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    Thanks Boomer. We can always count on your expertise. Going out to test this idea promptly.

    Rick

    Quote Originally Posted by boomers_influence View Post
    rav
    YES, it is very likely that you installed
    the gasket between the halves upside down.

    the gasket has a rectangular hole on the right front of the carb.

    thank you. boomer
    Edit - Yes, as Boomer suspected my gasket was installed incorrectly. An easier way to determine this is to notice the upper part of the DD13 has an asymmetric perimeter. If you have a segment of gasket exposed you know you have the gasket installed improperly. The rectangular hole he mentions as a feature in the gasket does need to be in the location he specifies.

    Now I need to determine why the engine will not catch and run. It cranks strong. I suspected fuel prime so, I added < 1 oz of fuel to the DD13 to help with this. The pump diaphragm/pump interface or my fuel supply line was weeping fuel momentarily but, this appears to have stopped. I smell fuel after short attempts to start the engine.

    Coil resistance values are within the ranges specified in the manual, wires were ~1.8 kOhms, the spark plugs are new and are gapped at .025"

    C'mon Onan...run already!

    Edit 2 - No spark...time to check the points or call David Kirk as I have his Points Saver.
    Last edited by RAVC1; 06-19-2017 at 07:24 PM.

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    Super Moderator tss8690's Avatar
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    I recommend checking the points gap and replacing the condenser.

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    No condenser if he has the point savers, It is removed.

    Do you have power to the coil? Just check, turn key to on and with test light, alligator clip to batt negative,, stick the needle end of test light on coil positive post. You should have power in all key positions, including start, with key off,, you should have no power.

    Really, as long as you have fuel, power to the good coil, the motor should start and run till it is out of gas. Or, at the very least, spit and sputter if the timing is off.

    If you have power to coil, and it doesn't start,, try this, with carb top off, as you turn the starter over, squirt a little bit of gas down the carb throat (tiny bit of gas is maybe 1/2 oz at most. What you want to see is if it will cough and momentarily start.

    As well, when you turn the motor over,, is the points saver indicator light, flashing on and off?

    FYI, even a brand new set of points,, I ended up having to run a very fine piece of emery across the points, otherwise they wouldn't ground out,,
    Last edited by Lionel; 06-20-2017 at 07:55 AM.

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    To test point saver, and check timing at the same time,

    Watch the timing hole in the front engine shroud. The point saver light should be on just prior to the flywheel getting to the timing mark, 21 degrees. As it passes this area, the light should go off (points opened) about halfway around with flywheel, the light should turn back on,, (points closed) and each and every time it goes past 21 degrees, it should go off. If it does that, my guess is it's working correctly, and your timing is good.

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    ssmewing (06-20-2017)

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    Lionel, all,

    PointSaver passed all tests with points removed from the ignition system (David returned my email with specific tests to perform to assess his PointSaver.). This suggested the points. I began with a simple cleaning and installed the cover. The B48M started with ease on the initial turn of the key! Life is better now.

    The only remaining concern I have is the fuel seepage from the supply line or, more likely, the interface between the diaphragm gasket and the polymer pump body. I illuminated this area with a flash light and watched it intently while the engine ran. I did not observe fuel seepage during the brief period I let the engine run. More similar yet, longer testing and carb adjustments, today to increase my confidence that the fuel system is safe then on to more deck modifications and mowing.

    Thanks for the involvement in my need for assistance. There is no doubt I like these tractors because, they are robust. However, they do beat us up on occasion.

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    jfk (06-20-2017)

  13. #8
    Senior Member ssmewing's Avatar
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    Quote Originally Posted by RAVC1 View Post
    Thanks Boomer. We can always count on your expertise. Going out to test this idea promptly.

    Rick



    Edit - Yes, as Boomer suspected my gasket was installed incorrectly. An easier way to determine this is to notice the upper part of the DD13 has an asymmetric perimeter. If you have a segment of gasket exposed you know you have the gasket installed improperly. The rectangular hole he mentions as a feature in the gasket does need to be in the location he specifies.

    Now I need to determine why the engine will not catch and run. It cranks strong. I suspected fuel prime so, I added < 1 oz of fuel to the DD13 to help with this. The pump diaphragm/pump interface or my fuel supply line was weeping fuel momentarily but, this appears to have stopped. I smell fuel after short attempts to start the engine.

    Coil resistance values are within the ranges specified in the manual, wires were ~1.8 kOhms, the spark plugs are new and are gapped at .025"

    C'mon Onan...run already!

    Edit 2 - No spark...time to check the points or call David Kirk as I have his Points Saver.
    You simply cannot have any leakage at the fuel pump or the fuel line. I hope that all the gaskets are new as well as the plastic valve body.

    New fuel line is a must as well. Tank to pump and pulse line. Use fuel line clamps.

    As for spark as others have said you have to trace the voltage. The repair manual has the test procedure.

    Sent from my XT1097 using Tapatalk

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    Super Mod jfk's Avatar
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    I find when the points are in good shape and working mechanically as they should a shot of brake cleaner works wonders!

    Thanks
    Jim

  15. #10
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    ssmewing,

    All carb, pump parts, fuel line, fuel filter (single Wix inline filter), pulse line and, plugs are new. I use fuel line zip ties not band or, worm gear clamps. I work as a marine mechanic and they are specified for OE use so, they are suitable and known to be safe. I followed Lionel's order for installing the pump parts, gaskets and diaphragm so I am good in this regard. Note some minor wrinkling of the diaphragm is evident directly above and below the center of the diaphragm (along the long, horizontal edges - top and bottom - of the pump). If you install the diaphragm adjacent to the pump cover plate the wrinkles are more severe. All assembly screws are tight but, I may add washers for the fuel pump screws to increase my confidence before returning the 446 to routine use.

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