Modern Vespa

Hello fellow Vespa fans. I've spent the last two days with Google Gemini and a multimeter working on my friends 250. It's a 2006 w/ 3,800 miles. He went over railroad tracks and the scooter died. I've been through the kill switch, stator connector, coil lead in and out, negative ground, etc... Please look at the photo for the conclusion AI gave, and provide some input. There were no visible signs of breach in the harness, or even the slightest wiff of something burning. I'm not after witty, snarky answers from people with too much time on their hands looking for a fight. If you've been down this road, I'd appreciate your feedback. Thanks in advance!

Does the injector spray fuel?

Is the spark plug lead in its place?? On older models it was kind of short and they had the tendency to unplug from the coil over huge bumps…

The spark plug caps are also prone to the small internal C-clip corroding to dust so the spark plug cap just sits on the plug without gripping it - and falls off when bumped. Happened to two out of five Vespas on the recent 1840-mile Pacific coast tour - one of which was mine!

One of the first steps was spraying starter fluid. It's a no spark problem. I've been using a brand new cable and ngk cap through this. I have removed the coil and it is resting on the floorboard fully connected. I've been over every electrical connection numerous times. One of the early things I did was test the coil, lead, cap and plug with a 9V battery. A spark jumped.

I had this issue on my 2009 GTS300. Everytime I went over a hard bump the scoot will give a hiccup. Replaced sparkplug, injector, cleaned throttle body, etc, but no success.

One day I went over a hard bump and it died totally. Turned out someone had replaced the screws that holds the seat hinge onto the body with slightly longer ones. Everytime the body under the hinge flexed from my weight on the seat this bolt pushed on the fuse under the hinge, cutting connection . Untill the day it pushed the fuse to far.

So check this fuse.

Is that the 10 amp fuse going to the fuel pump? On the 250 it's on the side next to the relay. Thank you for the reply.

ok, I wanna say that I am not super familiar with Vespa electrical continuity, but...... i know that they can be finicky.

1. does the coil require a proper ground to the frame when mounted ??

2. is it possible that the voltage regulator has ''popped'' inside breaking the cycle from the ecu thru the voltage regulator then to the coil to throw the lightning. is it even inline with what is needed to obtain spark?

the 250's had weaker regulators. I've had 2 fry and melt my headlight with 17 volts. both of those had less than 5k miles of use. why did they crap out ? who knows... both stators were fine.

3. could the violent jarring of the railroad tracks shake loose the allowable tolerance of the tone ring for the security communication to the ECU. then it would never allow a start signal to be sent. would the security light activate during this ??

4. both brake switches work properly ? they're kinda fragile and they have been known to malfunction.

Im just trying to help ya shoot in the dark.

you double confirmed that the kill switch works but the symptoms still say that it could be it. they can be sporatic.

Insert a poor attempt for me to not have to make assumptions

No. The coil has an ignition (and ECU switched via a relay) 'permanent' +12V on one side of the coil, and the other side of the coil is pulled to ground then released by the ECU whenever a spark is required.

I gather he's completely on top of the usual culprits.

So now it's down to directly testing the o/p of the ECU with a suitable test LED - if that fails then it's deffo the ECU - which might even be behaving correctly for some unknown reason. If the LED works then it's an open circuit somewhere between the ECU o/p and the coil -ve terminal.

Yep, I've beat this to death. AI is saying ECU. I have close to 20 hours w/ a multimeter into this. All the easy hanging fruit was eliminated. Keep the thoughts coming though. Thank you fellas.

Read this thread:

DIY Diagnostic tool for injection Vespa's with MIU ECU

Get a laptop and get IAWDiag. The KKL cable and Fiat adapter can be snagged off of Amazon cheaply. I'll find links if needed. On the GTS 250 and earlier 300s, the K-Line and L-Line on the Fiat adapter seem to be reversed (at least on the ones I've worked with), you may want to pull the insert out of the diagnostic plug on the scoot and plug the adapter in upside down.

I'd use it to establish if the ECU is dead or not. If the cables and connections are good and you have the COM port adapter set right, it should report the ECU data back when you connect.

There are a bunch of parameters you can enable and check, plus you can check for fault codes if the "left bank" coil is failing to fire.

And the contact of the lateral stand?
Often faulty on other bikes too.

Good stuff. Thank you!

Those who think the ECU is in 'no start' mode are missing the point that it's been proven that the fuel pump primes OK on switch-on, there's +ve power to all the 'fuel loads' (coil, fuel pump and injector), and the ECU appears to work completely OK *except* for providing the correct signal for the coil. Note the coil itself has been proven OK.

Yes, the AI could be correct that the internal pull-down transistor feeding the coil in the ECU could be o/c, but instead the external connector could be corroded or the wire from the ECU to the coil could be broken. Those scenarios can be tested. The ECU itself can also be tested with a test LED on the o/p.

Thank you Jim. I don't know what o/p and o/c mean.
Could you please elaborate on this some?
" the external connector could be corroded or the wire from the ECU to the coil could be broken. Those scenarios can be tested. The ECU itself can also be tested with a test LED on the o/p."

I suspect "o/p" is "output".

How about this. I have another friend who has a 2007 GTS250 in good working order. He generously offered up the TB/ECU of his bike to try in the 2006. Getting it on and off is pretty straightforward. 1. How do I navigate the chipped key(s)? 2. Is this a good idea? Thank you in advance.

I would pull the glovebox and the antenna ring, letting it dangle. Hold his key near the ring, and use the scoot's key to switch the scoot on.

Ok, I've worked on this a bit more. I unhooked the harness going into the ECU. Key is off, negative battery terminal removed. Set my meter to ohms, clamped the black probe to the rear shock bolt. I came up with 7 ground pins on the connector. AI tells me it should only be 4. I've aborted the idea of swapping throttle bodies. I already have 1 non running 250 sitting here.

That's the best way to test the wiring! I didn't suggest it because friends like that are rare.

It does entail both of you having Master keys. Swap his throttle body into your scoot, and swap the RFID chip from his Master key into yours.

Try to start - if it does, you have a failed ECU. The best scenario is that it won't start (lack of spark with everything else, fuel pump etc working). Then you *know* it's an o/c (open circuit) bit of wiring between ECU o/p (output) and coil.