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Thread: ECM correction after new fuel pump

  1. #1
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    ECM correction after new fuel pump

    I've re-installed my rebuilt fuel pump assembly with new pump, and after priming the bike fired up and idled great. Didn't have time for a ride after that, so it sat a couple days. Fired it up yesterday and it idled rough, fluctuating between 800-1500 rpms, and died a couple times. Always fired right back up and idled all over the place again. When it warmed up it seemed to hold idle better, so I took it down the street and it coughed a bunch through the throttle body, backfired, and died. Babied it back to my driveway, and am wondering if maybe the previousyl failing fuel pump had caused the ECM to adjust for the lean scenario, and now needs to be re-calibrated. I was going to re-load my original map that used to run great before the pump died, and re-set TPS as a baseline, but was wondering if this is common after re-installing a new pump. Also, how quickly does an ECM adjust itself? I'll report back how it runs after re-setting the ECM fuel and TPS.

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    Senior Member 34nineteen's Avatar
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    If the pump was failing and pressure/flow was low, the bike probably saw itself as running lean and fattened up the AFV to compensate. I would also check the plugs to make sure they didnt foul.

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    Quote Originally Posted by 34nineteen View Post
    If the pump was failing and pressure/flow was low, the bike probably saw itself as running lean and fattened up the AFV to compensate. I would also check the plugs to make sure they didnt foul.
    Yeah that's what I was hoping. Was saving the new plugs for when I rotate the engine but may drop em in sooner just to rule it out.

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    Senior Member 34nineteen's Avatar
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    Quote Originally Posted by RidetheLightning View Post
    Yeah that's what I was hoping. Was saving the new plugs for when I rotate the engine but may drop em in sooner just to rule it out.
    Just pull them and clean them. I'd get ahead of this now, because once you start the rotate, you will have a million other things on your mind, especially since its the first time. Hey, I was so preoccupied I forgot to install the O2 sensor!

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    Senior Member Cooter's Avatar
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    The ECM will adjust AFV pretty quickly and thats certainly easier to check before you open the tune nightmare.

    IMO, re-check your work before adding more variables. No shame in making a mistake, only in not looking for it
    Did you have the airbox off? Throttle body to airbox base gasket OK?
    Was there a few attempted starts before it ran? Fouled plugs. They are easy to swap without a rotate. Use a short length of 3/8" fuel line shoved on the plug as a flexible extension to thread in the new one.
    Fuel pump connection OK?
    Was the sock disintigrating? Did you get debris in the fuel line?
    Did you check for chaffed wires inside?
    If it doesn't idle well, it won't run well
    Once the little things are checked, I would re-start diagnosis as if I never touched the fuel pump.

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    Hunting idle and coughing through intake are sure signs of a lean condition. Did you replace all of the seals and o-rings on your pump assembly and did you check the fuel pressure afterward? The ECM will compensate for low fuel pressure by raising the AFV dramatically, so fixing the pump would make it run rich until the AFV is dialed back down.

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    hooked up to ECMdroid lat night and had a battery voltage code. Got my battery tested then charged. Re-loaded my fuel map, reset TPS, and adjusted the clutch cable (something I've been meaning to do already). Tonight I'll check out the plugs, which should be the last thing before I try again. Unfortunately between work and kids I have to work on it in very small increments.
    Last edited by RidetheLightning; 02-03-2021 at 09:39 PM.

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    Quote Originally Posted by RidetheLightning View Post
    hooked up to ECMdroid lat night and had a battery voltage code. Got my battery tested then charged. Re-loaded my fuel map, reset TPS, and adjusted the clutch cable (something I've been meaning to do already). Tonight I'll check out the plugs, which should be the last thing before I try again. Unfortunately between work and kids I have to work on it in very small increments.
    Checking your AFV should always be step 1 and can be done in about a minute. If it adjusts itself to a number significantly higher than 100 that is normally indicative of low fuel pressure. When you load a new "map" it is usually defaulted to 100. If the fuel pressure is low it may not even start at 100. If you adjust the AFV to say 120 and it starts then you know you have a fuel problem.

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    Quote Originally Posted by upaero View Post
    Checking your AFV should always be step 1 and can be done in about a minute. If it adjusts itself to a number significantly higher than 100 that is normally indicative of low fuel pressure. When you load a new "map" it is usually defaulted to 100. If the fuel pressure is low it may not even start at 100. If you adjust the AFV to say 120 and it starts then you know you have a fuel problem.
    Just realized I never said, but I checked it and it was 83.5% before I re-loaded my map. Got the new plugs in except I'm still struggling to get the boot back on the rear plug. Any tricks would be greatly appreciated.

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    Ah, ok. At the ~1100' elevation of Phoenix 83.5 is very low, and explains why your bike was running so bad. It's very common (more often than not I would bet) for these bikes to run unnecessarily lean because the ECM thinks the bike is going up a mountain. Reset the AFV to 100 and keep an eye on it to make sure it doesn't go down below about 98. I run my bikes in open loop with the O2 sensor still active to warn me of a lean condition , instead of allowing the ECM to adjust for it. rev-mo.com/openloop. What exhaust and mapping do you have? The EBR tune for the Jardine muffler has a nasty tendency to do exactly this. That causes a lot of decel popping which eventually causes the can to come apart.



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