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Newbie's headache - 2022 C400GT crank no start

ckwan

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Joined
Apr 27, 2026
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Location
Bay Point, CA
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Hello folks of BMW-Scooters! This is my first post and my first European Scooter. So it might not be smart to buy 2nd handed ones, but a bit too late now. Okay, here we go.

About me:

47yo male, mechanically inclined, former automotive technician, lives in PR California.

About my bike:

2022 C400GT (USDM), 16738 miles on dash, original BMW battery, fully charged float voltage at 12.5-12.8V. 20% front tire, bald rear tire. Not one time started, nor coughed, since I bought it.

Initial approach:

When I saw the ad of the bike, I went there to check on it. With the tires as Pirelli Angels in brand and with threads left as mentioned above, obviously the bike ran before. But I tried several times, engine turned, but no start. So I started to go through the basics: spark, fuel, air, compression. With bike powered on, I hear fuel pump humming for 3-5 seconds. And with fuel hose removed, fuel was pumping out healthily through outlet. Tested spark when attempted to crank while putting coil and spark plug against engine metal,.I saw steady output of spark there. And when I removed the fuel injector to test it while cranking, it squirted fuel out evenly in mist.
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I was stunned a bit when I found fuel and spark were present. Also, I was surprised that the service manual I found online, was not ideally the same for our USDM vehicle.
Screenshot_20260405_100916_Adobe Acrobat.webpScreenshot_20260405_100851_Adobe Acrobat.webp20260405_092045.webp20260405_093153.webp20260405_093200.webp
And I tried to go through YT videoes related to this issue, only to find another discrepancy between US and EU vehicles. On my bike, the Idle Control Valve/Solenoid was not even there to begin with.
20260422_104907.webp

But then I noticed the C400GT came with e-gas, a ride-by-wire throttle. Also, I noticed that when I powered the bike on, initial screen, aka., lamp check, showed no MIL lit. Without check engine light shown when keyed on, that is a tell tale sign of no communication of ECU. That makes me to believe that either ECU was bad, or some power or ground to the throttle body was compromised.

With that in mind, my goal now is to find the wiring diagram related to ECU and/or e-gas to figure out whether or not I need to replace my ECU into a new one.

To be continued..
 
Did the seller tell you anything about its condition? Sounds like no and you picked it up as a non-runner.
Since you have both spark and fuel misting from the injector, it would seem that the ECU is functioning. Although that spark plug looks very dry in the photo?
Then the three remaining things are:
- sufficient air to mix with the fuel, usually not the problem but useful to check anyway?
- timing, and
- compression
I would check compression first, then engine timing.
Let us know how it goes, and best of luck troubleshooting!
Get the Motoscan app to see if there are any codes.
 
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