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Thread: Another hard start issue - fuel priming problem?

  1. #1

    Another hard start issue - SOLVED! It's the IAC Idle Air Control

    I've got an '09 XB9SX, 20k miles, stock exhaust, stock ECM. Just got a Buelltooth and trying to figure out if I have a stock map. TPS reset done. Ever since I got the bike last year / 1000 miles ago, I've had the same problem. I ride in SF, CA where the weather is usually always 50-70F.

    Problem is that every time I start it cold, it takes 5-6 hits of the starter button before the engine catches. I can hear the fuel pump whine quietly for about 2 seconds, and the starter seems to whir up fine each time. I've tried the "Buell blip" with limited success. When it finally catches, I have to keep the revs high or else it is likely to die. But once the bike warms up, it rides really nicely without any lag on acceleration nor any burps. If I shut it down with the engine warm, it starts right up with a single hit, like any normal happy bike.

    Battery is a Deka EXT per recommendations here. 12.8V at start, drops to about 10.5V cranking. Even with a jumpstart pack separately, I get the same issues. Spark plugs looked good when I changed them out.

    I thought fuel pump could be suspect, but wouldn't that cause problems while riding? And the bike starts fine when warm.

    Any chance this could be a problem with initial fuel priming? I see the injector test on Buelltooth, but not sure what to look for. Would I be able to see fuel squirt out the injectors?

    Thanks all!
    Last edited by Endopotential; 06-15-2019 at 05:19 AM.

  2. #2
    Senior Member rb70383's Avatar
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    Did you just get this bike? Have you been able to see what maps are on the ECM yet? My 03 9R always was a little "cold blooded" I've tweaked the cold start to get it starting decently in cooler weather. Mid 30's.
    Lunatic is the fuel pump guru...
    But until then, If there are no other riding issues, loss of power, sputtering, loss of power at WOT, I would say the pump is OK. What is the Buell Blip? Blip the throttle while starting?
    To check initial priming, cycle the pump 2-3 times, before actually hitting the start button. If that fixes it, I'm not exactly sure what would cause that. Haven't looked into what holds the pressure in our fuel system. check valve or done by the regulator, or??

    Is this the only issue? No codes? Has mpg dropped? Does it smell rich? Speculation here...possible air temp sensor could be going. Enough to 'add' a choke to the bike. That can be seen on Buell tooth. Quick check once you get connected to the ECM, view live data and see if the live data matches the actual room temp. Obviously before the first start of the day.

  3. #3
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    It could be a goofy map.

    Load a stock one see if it cures your problem. That would be the easiest thing to do and just as easy to go back to your original map.
    I doubt its the fuel pump, it wouldn't run right no matter the engine temperature.
    Last edited by cossack84; 06-13-2019 at 01:35 AM.

  4. #4
    Thanks guys for chiming in.
    Will try to work on the ECM mapping over the next couple days. But that should only affect running, not initial startup no? Unless the map is really screwed up for low RPMs?
    The "Buell Blip" - I read somewhere here that you should hit the starter for a second to get the cylinder turning just to give it some momentum, then hit the starter again seriously to get the engine to catch.

    How do you go about tweaking the air fuel map for a cold blooded engine? Put in more gas for the low RPMs?

    Or at some point should I just give up and accept that "Harley engines are big and heavy, and take a lot of work to start"?

  5. #5
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    Quote Originally Posted by Endopotential View Post
    Thanks guys for chiming in.
    Will try to work on the ECM mapping over the next couple days. But that should only affect running, not initial startup no? Unless the map is really screwed up for low RPMs?
    The "Buell Blip" - I read somewhere here that you should hit the starter for a second to get the cylinder turning just to give it some momentum, then hit the starter again seriously to get the engine to catch.

    How do you go about tweaking the air fuel map for a cold blooded engine? Put in more gas for the low RPMs?

    Or at some point should I just give up and accept that "Harley engines are big and heavy, and take a lot of work to start"?
    Buells and modern Harleys are relatively easy to start. Sometimes they need a little extra (or a strong battery) to get over the compression on the first crank of the starter, but fire right up afterwards... as long as everything else is ok. If you are having fuel delivery, spark timing or other issues, you may have a cold blooded engine.

  6. #6
    Senior Member Cooter's Avatar
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    As long as the bike is cranking over fine, don't worry about the 'Buell Bump'.

    Try this: Cycle the key and run switch several times before tying to start it (adds fuel).
    or open the throttle slightly while cranking (adds air).
    If either of those let it start faster, it's narrowing down the possible issue.
    I would also use the live data on ECMDroid to check the temp sensor readings as it warms up. Make sure that sensor if good.

    To simplify, the fuel map doesn't really have a cold setting. It has "modifiers" that add a % of fuel for a specified time (referring to the map). That means a stock or race map won't matter, the engine is cold so it's not getting to closed loop or read the O2 anyway.
    Yes, you can change the modifiers to give the bike more or less fuel while starting. Buells have a VERY rich and VERY long cold setting as OE.
    I don't recall if ECMDroid has the option to change it with your Buelltooth dongle, but ECMSpy and TunerPro definitely do.

    Any fuel injected bike should start quickly and run well immediately no matter the engine temp. Good luck!

  7. #7
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    I had the same issue with my 09' XB when i purchased it a couple years ago. Turned out the plastic hose that goes from the fuel pump to the fuel regulator had two pinholes in it due to age. That caused the fuel pressure in the hose to drop after the pump would prime and caused the hard starting. It is not an uncommon issue since the plastic wears out over time. It is a cheap fix. You can contact Jacob Stark on the buellxb facebook page for details on a good replacement hose. While you are in there, you should probably also change out the fuel filter and the O-rings. You can see a tutorial on fuel pump removal here:

  8. #8
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    Lunaticfringe, referenced above, sells rebuild kits for the fuel pumps, he also knows a lot more than just about the fuel pumps.

    Have you tried iridium spark plugs ?
    Last edited by njloco; 06-13-2019 at 02:37 AM.

  9. #9
    Senior Member rb70383's Avatar
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    As stated, cycling the key/switch a couple times to prime the pump will help narrow it down as well.
    Only trick to start mine was slightly open the throttle on cold days.

    Have you ever got into the ecm at all? Or is this the first one you're getting into? The learning curve for first timers is a little steep, but clicks quickly.
    I use the buelltooth, and a tablet, then load the logs into my laptop where I tune the maps. I also use the tablet to do quick small changes if needed.

  10. #10
    I've tried keying the run switch several times before hitting the starter, thinking about that priming issue, but to no avail.

    I was able to get into the basics with ECM Droid. The map that was on the bike looks pretty close to the stock XB9 map that was sent to me by Buelltooth.
    Though I'm not used to seeing a fuel map with hexadecimal. I was expecting something with plain numerals. Though I haven't a clue how to fiddle with any of those values.

    IMG_0099.jpg



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